Simple Circuit Design

Adjustable Regulator Circuit Using TL431

2011-08-27T11:51:00.000+07:00

Here’s a circuit for simple Adjustable voltage regulator power supply circuit, at use integrated number circuit TL431. By from the circuit can fine volt 3V – 30V, depend on feed volt supply input and change the value R2, R1. This is the figure of the circuit;

It follow a formula calculates Vout = (1+R1/R2), Vref = 3V-30V, but this circuit gives current get not tall 100mA only. It just if want to enhance current, must use the transistor helps to enlarge current, such as 2N3055, TIP41 numbers or the other.

Simple Theremin Circuit Using Inverter Gates

2011-08-20T10:48:00.000+07:00

Here’s a design circuit for simple theremin circuit is constructed using only two inverter chip plus one regulator IC. This Theremin circuit is consists of five functional blocks: power supply regulator, hand controlled oscillator, null oscillator, mixer, and filter. This is the figure of the circuit;

The power supply regulator is consists of LP2950 regulator IC, which stabilize the voltage from battery to 5V. You can use more popular 7805 IC for this, but since the power consumption of this Theremin circuit is very small, then you can use 78L05 which is smaller. CR1 diode is used to protect from inappropriate battery polarity, shorting the battery voltage together with R8 100 Ohm resistor which prevent the large current when the battery is installed in wrong direction. Although the inverter chip will work well for 9V battery, there is a benefit of using voltage regulation to regulate the battery voltage at lower voltage level, that the voltage will remain constant for until the end of battery life. This will avoid frequency drift of the Theremin’s null oscillator which should be carefully adjusted to zero the output frequency, which can be affected by the supply voltage.

Simple TV Transmitter Circuit Using LM1889n IC

2011-06-06T07:59:00.000+07:00

This is a design circuit for a simple TV Transmitter Circuit Diagram and Circuit Board using LM1889n IC. This is the figure of the circuit;

The LM1889n consists of a sound subcarrier oscillator, chroma subcarrier oscillator, quadrature chroma modulators and RF oscillators and modulators for two low-VHF channels.

Simple Pressure Sensor Circuit

2011-06-06T07:51:00.000+07:00

Here’s a design circuit for a Simple Pressure Sensor Circuit Diagram and the PCB Layout. This sensor is based on the Lucas Nova Sensor NPC-410 Series pressure sensor. This is the figure of the circuit;

This circuit design utilizes an LM358 IC. The LM358 consists of two independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages.

Field Strength Meter Circuit

2011-06-06T07:50:00.000+07:00

Here’s a design of the instrument that is very useful for radio frequency (rf) engineer and hobbyist, especially when he/she has to adjust the final rf transmission. Setting up an antenna impedance matcher is one of the examples. This is the figure of the circuit;

The circuit uses only one transistor (MPSA18) as the active component. The signal strength meter display uses analog meter (1 mA full scale). This rf field strength meter has no absolute scale if we don’t calibrate the scale using a standard instrument, but the important thing for this un-calibrated rf meter is that it can display the changes of an rf field when we calibrate the antenna or the matching network for the rf transmitter-antenna loading. If we are tuning the antenna size or the transmitter-antenna matcher filter, then just observe the analog meter to get the maximum deflection.

Simple Sound Effect Generator Circuit Diagram Using HT2884

2011-05-25T04:51:00.000+07:00

Here’s a design circuit for Simple Sound Effect Generator Circuit Diagram uses the Holtek HT2884 IC to produce 8 different sound effects. This is the figure of the circuit;

The HT2884 is a CMOS LSI chip equipped with tone circuit, noise circuit, and other control logic to generate various sounds to be used in sound effects production. This IC features: single power supply (2.4V – 3.3V), low stand current, auto power-off function, and eight different sound sections.

Simple 9V Wireless Microphone FM Transmitter Circuit

2011-05-25T04:49:00.000+07:00

This is a design circuit for FM transmitter circuit can be used as a wireless microphone, can be received by an ordinary 88- to 108-MHz FM broadcast receiver. For the power supply, this transmitter circuit is powered by a 9 V battery. Here’s the figure of the circuit;

To comply with the radiation limit of FCC rules, keep the antenna length under 12 inches. L1 is 6 turns of #24 wire wound around a pencil or a 1/4″ form, with turns spacing of 1 wire diameter. C6 is a gimmick capacitor which has value about 1 pF.

Simple Magnetic Pre-Amp Circuit

2011-05-25T04:47:00.000+07:00

This is a simple design for pre amp. But in this design, it can be used for magnetic pickup for record players. The circuit based on uA741 IC that is used as an AC coupled non-inverting amplifier operating on a single supply. The figure of the circuit is shown in below;

The operation of the circuit is the amplifier gain is decided by the feedback components in which C2 controls the low frequency roll-off characteristics while C4 reduces the gain at high frequency end to compensate for the pickup characteristics.R3,R4 and R5 form a voltage divider to give a bias of about half the supply voltage to the non-inverting of uA741.The output at pin6 therefore stands at half the supply voltage.R5 and C3 form a supply line filter to reduce the hum level ans also to eliminate “growling” in case the preamplifier circuit is operated on a common supply with other circuits.

In this circuit, there are notes for attention. First, the circuit is assembly on a good quality PCB or common board. Second, mount the IC1 on an IC base. The circuit can be powered from a 12V battery or 12V DC power supply. Up to 24 V DC can be given to power the circuit. I prefer 12 V DC. Mono sockets can be used to connect the input and output.

Simple TRIAC Crowbar For AC Or DC Lines

2011-05-04T12:13:00.000+07:00

A TRIAC Crowbar circuit which works for both AC and DC voltage is shown in the schematic diagram below. This circuit is provide overvoltage protection for electronic or electrical equipment against excessive supply voltage. Crowbar circuit provides two level of protection.

First, this protection circuit will drop the voltage across the protected equipment to near zero by shorting the voltage, and second, the circuit will blow the fuse since it short the current. This is the figure of the circuit;

Using the values for R2, R3 and R1 as shown in the schematic diagram, this circuit can operate within range of 42 to 84 VAC or 60 to 120VDC. R2 set operating point where the crowbar will be triggered. To be safe, the TRIAC voltage rating should be greater than that triggering point, actually it should handle the highest possible voltage exposure. To accommodate testing, when we need to check if the crowbar action is triggered without blowing the fuse, a testing switch is provided (normally closed push button). An alarm unit can be added in parallel with the lamp for audible indication in testing crowbar action. [Circuit diagram source: seekic.com]

Simple Ham Radio Circuit Audio Filter Using 741 IC

2011-05-04T12:10:00.000+07:00

Here’s a design circuit that has function that it will help to filter out the interference signal and ensure that the signal received from the Morse code station stand out. This is the figure of the circuit;

The earliest mode of radio communications is the use of Morse Code on a continuous wave carrier(CW) which is interrupted to generate a dit and dah in forming an alphabet. Component: 741 IC, Resistor, Capacitor, Battery, Inductor, Switch.[Circuit diagram source: electronics-project-design.co]

LM380, Simple 2 Watts Audio Amplifier Circuit

2011-05-04T12:01:00.000+07:00

Small audio amplifier is useful for audio troubleshooting or simple audio projects. It should be a low cost and easy to build. Using integrated circuit for this purpose is the right choice. This is the figure of the circuit;

With LM380 audio amplifier integrated circuit, 2 Watts power can be delivered. For better thermal endurance, a large copper track can be printed in the board to provide heat sinking, this copper track should be soldered to pins 4, 3, 10, 5, 12 and 11.

AF/RF Signal Detector Circuit Using TDA2822 IC

2011-05-04T11:54:00.000+07:00

Here’s a design circuit for AF/RF Signal Detector Circuit Diagram. This circuit based on the TDA2822 IC. This is the figure of the circuit;

This circuit has features: very neat and easy to make, the loudspeaker is in use 4 ohm & 500mW.used to detect the signal does not AF / RF, cheaper cost, low power stereo amplifier in 8-pin mini-DIP IC, output power up to 250 MW. Component: Switch, Capacitor, Resistor, Transistor, Speaker, Diode. [Circuit diagram source; circuitdiagram-schematic.com]

FB20Hz High-Pass Rumble Filter, Subsonic Blocker

2011-05-04T11:33:00.000+07:00

Here’s a design circuit for 20-Hz high-pass rumble filter circuit. Rumble noise could come from many sources, such as wind blow around an outdoor microphone, mechanical disturbance on phonograph, or many other possibilities. We can remove this noise by filtering the signal before the amplifier. This circuit is designed for 20-Hz cutoff frequency and phonograph amplifier with gain 1-dB. Here’s the figure of the circuit;

Using large resistance value, this circuit is allowed to use lower-cost and smaller capacitors. This circuit assumed that only audible part of the signal is important, so it will remove sub-sonic signals. Don’t use this circuit for recording which contain many for subsonic signals as part of the information such as earthquake or meteor crash in movie’s sound.

Simple Digital Theremin Circuit

2011-04-19T19:35:00.000+07:00

Here’s a design circuit for theremin circuit uses digital component, so we can call it a digital Theremin. This circuit employs logic inverter 74C04 or CD4069 hex inverter and CD4046 phase-locked-loop (PLL) IC. The CD4069 logic inverter is operated as a fixed-frequency oscillator with frequency around 100kHz. The CD4046 is operated as a variable frequency oscillator which is adjustable around 100kHz. The exact center frequency of the on-chip oscillator is determined by R4, C2 and R3. This is the figure of the circuit;

The frequency of variable oscillator frequency circuit can be shifted several kilohertz by moving your hand approaching the antenna since the C2 and the antenna form an equivalent parallel capacitance. The frequency of the variable oscillator should be set to the same frequency of fixed oscillator when there is no hand or human body close to the antenna. This calibration is done by adjusting the zero control R4 pot with this simple rule: If both oscillators (the fixed and the variable) are set to the same frequency then the Theremin will produce no output (silent). This Theremin circuit will start producing audible tone if you move your hand approaching the antenna since it will shift the frequency of the variable oscillator. You can play this Theremin circuit by moving your right hand around the antenna and at the same time turning the volume knob R5 with your left hand. [Circuit diagram source: seekic.com]

Super Simple Inverter Circuit

2011-04-05T17:28:00.000+07:00

This is a design circuit of a simple inverter that can be used to power fluorescent lamp and a small strobe. This circuit will produce over 400VDC from a 12 VDC, 2.5 A power supply or marine battery or an auto. This circuit is very simple because it does not require custom transformers or coils. Also all components are readily available. This is the figure of the circuit;

The output of this circuit depends on the input voltage. If we use the component values given, we will get offer 400 V from 12 V supply and charge a 200 uF capacitor to 300 V in under 5 seconds. We must use a good heat sink because Q1 does get quite hot. D1 is used to prevents significant reverse voltage on the B-E junction and provides a return path for the base drive. R2 is used to limits surge current through D2.

WARNING: Output is high voltage and dangerous even without large energy storage capacitor. With one, it can be lethal.

Stabilized 3V Voltage Source/Reference

2011-04-05T17:23:00.000+07:00

This LM10 circuit can be used as low voltage low current voltage source or reference. This circuit regulate the voltage from the power supply to give a very stable output. This is the figure of the simple circuit diagram;

The minimum voltage level for powering this circuit require only 0.2V above the output level, showing the low drop out (LDO) feature of this circuit. [Circuit diagram source: National Semiconductor Application Note]

Light Level Droplets Detector Circuit

2011-04-05T17:19:00.000+07:00

Here’s a design circuit for Low-Light Level Drop Detector. This circuit utilize self-biasing configuration to detect small changes in light level. This circuit usually used in monitoring very low droplets rates. The collector of the transistor gives feedback that is used to stabilize the bias of the photo darlington. This is the figure of the circuit;

The effect on optical performance is reduced by a high base-source impedance that is produced by The 10-μF capacitor and 10-MΩ resistor. When there is a liquid drop is detected by the detector, the light that reach the chip is momentary decreased causing collector voltage to momentarily rise, then output signal is generated. Due to mechanical spacing system constraints and output power constraints on the LED, the initial light bias is small. A fraction of this initial bias is the change in light level. This fraction is caused by stray light paths and drop translucence. When biased, the output signals level is still acceptable because the photodarlington has high sensitivity. This compares with unacceptable bias point stability and signal levels when biased conventionally, like signal output across the collector bias resistor and base open. [Circuit diagram source: seekic.com]

Five Decade Dynamic Light Level Meter Circuit

2011-04-05T17:16:00.000+07:00

Here’s design circuit for a Portable light-level meter circuit with five-decade dynamic range. This uses a single cell battery as the power supply. To calibrate this circuit, use an appropriate illumination, then adjust R2 so that the output equals the reference. This is the figure of the circuit;

To make this circuit give output meter follows standard light meter, adjust R2 and R6. Maybe there is an error at the scale extremes because the log slope is not temperature compensated. An infrared-stop filter is recommended for this circuit because silicon photo-diodes (D1) are sensitive to near-infrared light. This circuit will give a excellent results if an appropriate correction filter is applied and a blue-enhanced photodiode for D1 is used. [Circuit diagram source: National Semiconductor Application Note]

Burglar Alarm Works for Both N.O and N.C Contacts

2011-04-05T17:10:00.000+07:00

Unlike other alarm circuit that provide normally-open only or normally-closed only configuration, this alarm circuit work for both configurations. The mechanism of this alarm circuit is very simple, that the output will be active (Q1 transistor will be conducting) if IC1 or IC2 “high”. This is the figure of the circuit;

If R2 is open, then IC1 output will be high since the non-inverting input voltage will be tied to V++. At this condition, IC2 will be low but it’s fine since the output of IC2 is connected through a diode to prevent ground short. If R2 is shorted then the voltage at pin 3 IC2 will go higher than the voltage at pin 2, so the output of IC2 will be high. At this time the output of IC1 will be low, but again, a diode (D1) will prevent the output to get shorted.

12V to 120V Power Inverter Circuit

2011-04-05T17:07:00.000+07:00

Ever needed a low power 120volt AC power source for your car, van or truck? Well this circuit should do the trick for you. It will supply 15 watts of AC power to a device. It should power lamps, shavers, small stereos and small appliances. If you draw to much power the circuit will shut down all by itself. This is the figure of the circuit;

The output of this circuit is a square wave so there may be some noticeable hum on audio units plugged into it. To reduce some of the hum increase the value of the output capacitor which is at .47uf now. That transistor in the circuit are high power PNP transistors. Radio Shack part number 276-2025 are good ones to use or TIP32. The transformer is a 24 volt 2 amp center tapped secondary Radio Shack part number 273-1512 or equivalent.

Very Simple Power Failure Light Circuit

2011-03-28T12:40:00.000+07:00

This simple circuit has many uses, from lighting up rooms and walkways in the case of a power failure, to monitoring and security uses. This circuit is a very basic power failure lighting circuit based around a relay. Here’s the figure of the circuit;

There are many different power failure circuits out there based on 555 timers or transistors but they all have different problems including limited input voltage, price and complexity, and poor backup power. This unit has been designed to work with mains power all the way down to 5 volts, and power 3 LEDs to provide light for a hallway or a child's room in the event of power failure. The PCB includes many simple add-ons and modifications too. This circuit is connected to ac power through J1 then rectified to dc through D1-D4. D5 is a 12 volt zener diode being used along with the resistor R1 and the coil resistance of relay RL1 to regulate the input voltage to 12 volts and C1 is used to help smooth this power. Alternatively a dc voltage of 5 volts or more can be connected directly to J2 and J3, positive to J2 and negative to J3; in this setup the circuit would not need J1, D1-D5, and R1. The relay RL1 is a SPDT 5vDc relay and when power is applied to it, it opens the circuit with the LEDs so they are off as long as power is on if the power goes off, the relay closes the circuit and the battery BAT1 powers the LEDs D6, D7, and D8. In this circuit BAT1 is a 9 volt battery that powers the 3 LEDs through R3; however BAT1 can be many different batteries depending on your needs. J4 is also available in parallel with the LEDs to connect a buzzer or etc.

Simple 300W Lamp Dimmer Circuit

2011-03-28T12:20:00.000+07:00

Here’s the figure of the circuit simple lamp dimmer uses only a Triac, a Diac and some other passive components to achieve power control on lamp . It is suitable for 230V incandescent lamps with a total power of up to 300 Watts.

At first triac TR1 is not conducting; C1 is charged through R1/P1 until the trigger level of diac D1 is reached. When the diac trigger level is reached (about 30 V), D1 fires and Triac TR1 is switched on. The triac will remain in conductive mode until the mains current is lower than the triac hold current at the end of the half mains period. This works for both the negative and positive mains period because both the triac and the diac are bi-directional. R1 is added to protect the potentiometer in the case of a short circuit. The fuse is absolutely mandatory as the discharge arc in a failing incandescent lamp is virtually a short circuit.

FM Radio Using TDA7000

2011-03-28T12:11:00.002+07:00

Here’s a design simple circuit using TDA7000 that can build an FM radio with a minimum of components; most of them so easy to manage, like the ceramic capacitors that do not require polarization and only two resistors. Here’s the figure of the circuit;

The components you will employ will be of small dimensions and low cost. Even the integrated circuit itself, the TDA 7000, is not of great cost.

Dual Relay Driver Circuit

2011-03-28T09:37:00.000+07:00

Here’s a design circuit for a simple and convenient way to interface 2 relays for switching in dual relay driver circuit. This is the figure of the circuit;

This circuit has input - 12 VDC @ 84 mA, Output - two SPDT relay. Power Battery Terminal (PBT) for easy relay output connection is a one part in there. The circuit has four mounting holes of 3.2 mm each.

DIY Water Usage Meter Circuit

2011-03-28T09:35:00.000+07:00

Here’s a design circuit for measure water usage. This is a simple circuit. Here’s the figure of the circuit;

Working with the interaction design team, a bunch of us at Teague have been tinkering with measuring water, analyzing usage data in real time to affect behaviors, and storing it to see patterns over time. At the heart of the exploration was a need to cheaply measure water from the tap. Water meters vary quite drastically in price (from $250+ for industrial grade sensors to $6 for garden hose attachments that limit total usage based on rough estimates). We settled on a $20 water meter used for PC cooling systems (the INS-FM17N by Koolance) due to its accuracy, low price, small size, and electronic sensing method that could be easily measured by a microcontroller.

Simple Touch Switch Using 4050 CMOS Buffer

2011-03-23T05:47:00.000+07:00

Many efforts has been made to make simpler circuit, and here is one result, a very simple touch switch. You can build up to 6 similar circuit using only one 4050 chip. If you touch the “on” pad, the output will be on remains on until you or some one the “off” pad. This is the figure of the circuit;

When the power supply is first applied, the output will be high because C1 capacitor trigger the buffer gate, after the output get high then the input will not depend on the C1 charging anymore because it maintained by the R1 that connect the output to supply voltage level. When the output is high, although the input is connected to the output via R1, if you touch the “off” pad, then the voltage of the input pin will be low because your skin resistance (below 1Mega Ohm) is much lower than R1 resistance (10 Mega Ohm). Because now the input is low, then the output will we low. Releasing your finger doesn’t switch back the output because now the input is connected to ground by the output via R1. If you touch the “on” pad when the output is low, the input pin will be high because your skin resistance is much lower than its output grounding via R1. After the input goes high then the output will switch to high and now the output will maintain the input remain high after the touching gone, via R1.

Simple Digital Ammeter Circuit Diagram Using DMS-30PC-0-RS

2011-03-19T08:02:00.000+07:00

This is a design circuit for a simple Digital Ammeter Circuit Diagram using DMS-30PC-0-RS from Murata Power Solutions. This digital ammeter is basically a very sensitive voltmeter with a typical input range of ±200mV. The circuit below depicts that the voltage across the shunt is only 0.1Vdc above pin 3 (5V RETURN). This is the figure of the circuit;

This is well below the ±2V common mode voltage limitation of the meter. The 0.1Ohm shunt, with 1.0 Amperes through it, will develop 0.100Vdc or 100mV across it.

Simple Positive (+) to Negative (-) Voltage Inverter Circuit

2011-02-21T10:59:00.000+07:00

This is a simple circuit that can be used to convert the positive input voltage become negative voltage. Here’s the figure of the circuit;

Component list:

Part    Total Qty.    Description
R1    1    24K 1/4 Watt Resistor
R2    1    56K 1/4 Watt Resistor
C1    1    3300pF 25V Ceramic Capacitor
C2    1    47uF 25V Electrolytic Capacitor
C3    1    10uF 25V Electrolytic Capacitor
D1, D2    2    1N4148 Silicon Diode
U1    1    555 Timer
MISC    1    Wire, Board

In this circuit, V+ can be anywhere from 4 to 16V. -V is one volt less than V+. So, for -12V output, use +13V input. The maximum current output of the circuit is about 280mA, more than enough for a few op amps. For better regulation, a 79LOxx series regulator can be used. A zener diode may also be used to regulate the output voltage.

Simple Galvanometer Circuit

2011-02-21T10:57:00.000+07:00

This circuit is design for galvanometer circuit. According to Wikipedia.org, a galvanometer is an analog electromechanical transducer to be used for detecting and measuring electric current (ammeter). In this circuit design, the voltage across Rm and Rv is the same because they are in parallel. The resistor Rv is a variable resistor. Here’s the figure of the circuit;

Simple R/C Circuit

2011-02-07T21:03:00.000+07:00

Here’s a design circuit for a very easy and efficient receiver for actuating garage doors, starter motors, alarms, warning systems and numerous some other possibilities. This is the figure of the circuit;

In this circuit specifies a whip or wire antenna which just indicates a solid piece of wire 6-12 inches long (15-30cm). The antenna coil is experiments, however you can start with ten to 12 turns of #22 (0.7mm) magnet wire, and 5/16" (8mm) coil diameter. Antenna wire is soldered at 1/2 turn of the coil and the gate of the BRY35 is soldered about halfway the coil. This circuit will transmit as much as 100-feet with the above specs @ 30uA. The relay coil is specify as much as 200 ohm but that's just the one I had in stock. Any low-ohm relay, even at 9V or so, ought to accomplish the task. And one remaining note, do not be expecting too a lot from this circuit. The "Very Easy R/C Circuit" is simply that; Easy!

The BRY35 is really an classic semiconductor produced by Philips. A great replacement would be the EC103D1, also produced by Philips (see pin-out picture for this device). NTE Semiconductors gives an alternative of NTE5405, but I have not attempted it. I think, a NTE5400 (30V) or NTE5401 (60V) will function just also. The NTE5405 is a bit overkill at 400V.

Simple LED Flasher Circuit Using LM3909

2011-02-07T20:59:00.000+07:00

This is a very -very easy and simple LED flasher circuit with only needs three components that are: a flasher IC, a LED and an electrolytic capacitor. Here’s the figure of the circuit;

Component list:
LED1_________Red LED
C1___________100uf/16V
IC1__________LM3909

Infrared Modulation Identifier Circuit

2011-02-07T20:50:00.000+07:00

This is a design circuit for Infrared Modulation Identifier using remote control. Here’s the figure of the circuit;

In this circuit illustrates how the modulated carrier of infrared is measured by displaying the waveform on a frequency counter after the signal received is amplified.

Simple Electronic Combination Lock Circuit

2011-01-26T19:59:00.000+07:00

This is a design circuit for a very easy and simple electronic combination lock based on IC LS7220. This could be the circuit diagram of a easy electronic combination lock by using IC LS 7220.This circuit may be applied to activate a relay for controlling (on & off) any device each time a preset combination of 4 digits are pressed. The circuit may be operated from 5V to 12V. This is the figure of the circuit;

To set the mixture connect the appropriate switches to pin 3,4,5 and 6 of the IC through the header. As an example if S1 is connected to pin 3, S2 to pin 4 , S3 to pin 5, S4 to pin 6 of the IC ,the combination is going to be 1234.This way we can create any 4 digit combinations. Then connect the rest of the switches to pin 2 of IC. This will cause the IC to reset if any invalid key is pressed , and entire key code has to be re entered. When the correct key combination is pressed, then the output ( relay) will be activated for a preset time driven by the capacitor C1.Here, it is set to be 6S.Increase the value of C1 to increase the preset time.

For the keypad, arrange the switches in a 3X4 matrix on a PCB (Printed Circuit Board).Write the digits on the keys by using a marker. Instead of applying numbers I wrote some symbols!.The bad guys is going to be more confused with this.

Component Part List:
·   C1 = 1uF 25V
·   C2 = 220uF 25V
·   R1 = 2.2K Ohm
·   Q1 = 2N3904 / 2N2222
·   D1 = 1N4148 / 1N4001-1N4007
·   K1 = 12V SPDT Relay / Any appropriate relay with 12V coil
·   U1 = LS7220 Digital Lock IC
·   S1-S12 = SPST Momentary Pushbutton Keypad (see notes)
·   HD1 = 12 Position Header

Simple Adjustable Sine/Square Wave Oscillator Circuit

2011-01-26T19:45:00.000+07:00

This is a design circuit for simple easily tuned / adjustable sine and square wave oscillator. This is the figure of the circuit;

This circuit provides sine and square wave at frequency of below 20Hz up to above 20KHz. The benefit of this circuit diagram is that you can adjust the output frequency by varry the variable resistor of R6.

Simple Ni-Cd Battery Discharge Limiter Circuit

2011-01-24T16:44:00.000+07:00

This is a very simple Ni-cd battery discharge limiter electronic project can be designed like in this circuit diagram using few common electronic parts. This circuit is very simple and can be used in many compact designs. This circuit disconnects the battery from the load when the output voltage falls bellow a preset level. C1 charges through R1 and turns on Q2. This is the figure of the circuit;

Collector current flows through R2 turning Q1 on and battery is connected to the load. When the output voltage falls bellow a point set by RV1, Q2 turns off, Q1 turns off and further discharge of the battery is prevented. The maximum output that can be supported by this discharger circuit is around 3 amperes. At the input you can connect on or two 12 volt Ni-Cd batteries.

Simple Ham Radio Circuit For Audio Filter

2011-01-24T16:42:00.000+07:00

One of the earliest modes of radio communications is the use of Morse Code on a continuous wave carrier (CW) which is interrupted to generate a signal in forming an alphabet. Though it looks simple, this method is often makes less reliable as the surrounding man-made noise and atmospheric noise caused interference to the receiver station. This project will help to filter out the interference signal and ensure that the signal received from the Morse code station stand out. The circuit design of the filter circuit is simple and easy to build. Figure below shows the filter's selectivity response curve. It is sharp at the peak at 20dB at the audio frequency of 800kHz - 900kHz;

It uses common parts that can be purchased easily from any electronic shops. At the core of the circuit is a OP AMP where its input is connected to the headphone jack of the receiver. Some of the amplified signal is feedback through potentiometer VR1 to the non inverting input which helps to boosts the gain and hence called positive feedback. Some is passed to the inverting input through a LC circuit. This cancels the gain of the amplifier except at the resonant frequency - high impedance at resonance state. The amount of positive feedback is adjusted using the potentiometer VR1.

L choke should be in the region of 5H but this is not critical. Try using the winding of an audio transformer to make this choke. The output of this filter is connected to the earphones. On Switch SW and on the radio. Vary the VR1 until it goes into oscillation and then turn it back a bit. Tune across the code station and you will hear a sharp peak response effectively cutting off other noise and interference.

Simple Regulated Charger Circuit

2010-12-27T21:12:00.000+07:00

Most of the battery chargers do not have current and voltage regulation provisions. The step down voltage is simply used for charging. These chargers develop internal resistance so the output voltage drops when the battery is connected to the charger. This is a design circuit for the charger circuit. This is the figure of the circuit;

0-15 1 Ampere step down transformer drops 230 volt AC into 15 volt AC which is rectified through the bridge rectifier comprising D1 through D4. The rectified DC is then made ripple free by C1 and send to the collector of the medium power NPN transistor T1 to give regulated output. Resistor R1 and Zener diode ZD are used for both voltage and current regulation. Output current from the emitter of T1 depends on the value of R1 which can be changed according to the requirement using the ohms law. 12 volt Zener diode gives constant 12 volts to the base of T1 so that output voltage remains 12 volt irrespective of the input fluctuations. Diode D5 is polarity protector that prevents short circuiting if the polarity of the battery is reversed. LED indicates the charging process.

Simple Logarithmic LED Bar Display Circuit Using AN6884 IC

2010-12-21T13:09:00.000+07:00

This is a circuit for a logarithmic scale LED bar display driver. AN6884 accept wide range of supply voltage, ranging from 3.5V to 16V. This VU (voltage unit) bar display circuit provides only 5 levels, but will accept wide range of input level because the scale is logarithmic: -10, -5, 0, 3, and 6dB points. The output current for each LED will be constant at 15mA, suitable for most LED types. This is the figure of the circuit;

To operate at voltage higher than 6V, a current limiting resistor R should be inserted between Vcc and the LEDs anodes, and the values should be chosen as shown in the table for appropriate power supply voltage and maximum operating temperature. This circuit is suitable for monitoring audio level of your amplifier’s output. If you need only to measure DC voltage level then the 2.2uF electrolytic capacitor can be omitted. [Circuit's diagram source: Panasonic Application Notes]

Simple LDR Light Alarm Circuit

2010-12-21T13:07:00.000+07:00

This circuit is a design for a light alarm circuit. This circuit uses Light dependent resistor (LDR). When there is no light fall on the LDR, the transistor driving the speaker is not turned on, because its resistance is high. When the LDR receives light, its resistance decreases and the collector of the second transistor falls. This is the figure of the circuit;

The first transistor turn off slightly, via the second 100n. The base of the second transistor receives additional spike from the first 100n. It continues until the second transistor is turned on. The second transistor cannot be kept turned on because the first 100n is now nearly charged. To produce the second half of the cycle, both transistors swap conditions and The second transistor is turned off.

Simple Emergency Light Circuit

2010-12-21T13:05:00.000+07:00

This is a design circuit for an emergency light is a battery-backed lighting device that comes on automatically when a building experiences a power outage. This is the figure of the circuit;

If AC supply is present, the alternating voltage is passed through diode D1. D1 behaves as a half wave rectifier and lets only positive voltage to pass on. When AC supply goes off, capacitor C1 discharges through R3. Due to this discharging of C1, voltage across C1 decreases gradually.

Part:
R1, R2 _____200k – 1W
R3 ________100k – 1/2W
R4 ________100k – 1/2W
D1 ________IN4004
C1 ________0.1mF – 50V
T1 ________BC148B
T2 ________SL100
Dry cell battery 1.5V
Bulb 3V

The Simple Gentle Touch Circuit

2010-12-10T02:28:00.000+07:00

This is a circuit for gentle touch. The approach requires that a microcontroller is already available in the circuit, and a spare input port pin and a spare output port pin are required, along with a little software. When power is applied T1 initially remains turned off. When the button is pressed the gate of T1 is taken to ground and the p-channel power MOSFET conducts. The microcontroller circuit is now supplied with power. Within a short period the microcontroller must take output PB1 high. This turns on n-channel MOSFET T1 which in turn keeps T1 turned on after the push-button is released. This is the figure of the circuit;

The circuit itself draws no current in the off state, and for (rechargeable) battery-powered appliances it is therefore best to put the switch before the voltage regulator. For mains-powered devices the switch can also be fitted before the voltage regulator (after the rectifier and smoothing capacitor). Since there is no mains switch there will still be a small standby current draw in this case due to the transformer. Be careful not to exceed the maximum gate-source voltage specification for T1: the IRFD9024 device suggested can withstand up to 20 V. At lower voltages R2 can be replaced by a wire link; otherwise suitable values for the voltage divider formed by R1 and R2 must be selected.

Simple Dancing Lights Circuit

2010-12-10T02:24:00.000+07:00

This is a design circuit for a simple circuit which can be used for decoration purposes or as an indicator. Flashing or dancing speed of LEDs can be adjusted and various dancing patterns of lights can be formed. This is the figure of the circuit;

The circuit consists of two astable multi vibrators. One multi vibrator is formed by transistors T1 and T2 while the other astable multi vibrator is formed by T3 and T4. Duty cycle of each multi vibrator can be varied by changing RC time constant. This can be done through potentiometers VR1 and VR2 to produce different dancing pattern of LEDs. Total cost of this circuit is of the order of Rs 30 only. Potentiometers can be replaced by light dependent resistors so that dancing of LEDs will depend upon the surrounding light intensity.

Muscular Bio-Stimulator Circuit

2010-12-10T02:09:00.000+07:00

This is a circuit for muscular bio-stimulator circuit is small and portable. This circuit provides muscles’ invigoration and stimulation but in major it could be an aid in removing cellulite. To use this bio-stimulator we just put the electrodes to the skin at both ends of the chosen muscle and then rotate P1 knob slowly until we feel a mild itching sensation. This is the figure of the circuit;

IC1 generates 150µSec. pulses at about 80Hz frequency. As a buffer we use Q1 and to inverts the polarity of the pulses and drives the Transformer Q2. P1 is used to set the amplitude of the output pulses and the brightness of LED D1 displays the approximately . To protects Q2 against high voltage peaks generated by T1 inductance during switching this circuit uses D2. This device is forbidden to use for pregnant women and Pace-Maker bearers . Do not put the electrodes on varices, cuts, injuries or wounds. Obviously we can’t guarantee any therapeutic effectiveness for this device.

Simple FET Op Amp Circuit

2010-11-01T10:03:00.000+07:00

This is a design circuit for Simple FET Op Amp. The FM3954 monolithic-dual provides an ideal low-offset, low-drift buffer function for the LM101A op amp. The excellent matching characteristics of the FM3954 track well over its bias current range thus improving common mode rejection. This is the figure of the circuit;

Circuit source: National Semiconductor Application

Simple Shunt Series Pair Wideband Amplifier Circuit

2010-10-23T01:41:00.001+07:00

This is a circuit for a Shunt Series Pair Wideband Amplifier circuit. This circuit has four feedback loops, they are two emitters feedback, shunt-shunt feedback and an AC feedback loop(series-shunt). This is a very stable circuit and can be used for wideband amplifiers and low gain. This circuit requires +12 supply that restrict the “headroom” of the second resistor. The emitter of the second transistor feed the a shunt-shunt feedback resistor whose upper end that can give more current without causing a grater voltage drop in the collector resistor. This is the figure of the circuit;

Beside shunt-shunt feedback, this circuit has an AC feedback loop(series-shunt). The DC bias is blocked by 0.1uF capacitor. The amplifier has gain of about 12 if AC feedback loop is removed. AC feedback loop’s gain is 2.8, so this circuit has gain of 3.16. At 1Khz, the gain of this circuit is 3.11. Be careful large loop gains are dangerous at high frequencies.

Simple Peak Detector Circuit

2010-10-23T01:40:00.006+07:00

This is a circuit that had detects the peak voltage of the input waveform Vin and outputs it as Vout. This is the figure of the circuit;

The circuit uses a dual operational amplifier IC, the 1458, which is a single IC package that houses two individual op-amps. In this circuit, the first op-amp is used as a voltage follower whose output is used to charge the capacitor C1 through D1. As such, the voltage to which capacitor C1 charges up to is the maximum voltage that the input waveform reached, i.e., its peak voltage.

The second op-amp of the 1458 is used as a buffer that outputs the capacitor voltage with negligible loss in the capacitor charge. The reset switch is used to discharge the capacitor if a new input peak voltage needs to be detected.

Simple Passive Treble Control for Guitar Pedal

2010-10-23T01:40:00.003+07:00

The R1/C1 network makes a low pass filter when the wiper is at the grounded end of the tone pot, and there is a treble cut. The C1 cap bypasses R2 when the wiper is adjusted so that it is at the top end of the pot and it creates a treble boost. This is the figure of the diagram;

The 100k output volume and the 100k tone pot are always in parallel as a constant load. It’s suggested to used a linear taper pot for the tone control and a log (audio) taper for the volume control. Suggested values for initial experimentation are R1=10k, R2=47k, and C1=0.022uF. Some signal loss, as with any passive network is the limitation of this combined tone control. However, many guitar pedal designs have strong enough output signal level, and this tone control is an excellent option for those circuits with enough drive.

Simple LM2576 Switching Regulator

2010-10-23T01:38:00.002+07:00

This is a circuit that can be used to produce any output voltage, an external feedback resistors can be added. The sLM2576 is a Switching Regulator that can produce 15, 12, 5, 0r 3.3V output voltage from maximum supply voltage of 60V or 40V. This LM2476 featured with voltage reference, switch and feedback path for use in either the negative boost or the buck saturation voltage of The LM2576 switch is typically 1.4V. A heat sink may be needed to solve the power dissipation, however the thermal dissipation is internally limited. The LM2576 has quiescent current of 50 µA in standby (on/off high). This circuit is a testing circuit for LM276. This is the figure of the circuit;

The electrolytic capacitors at output and input should be connected with leads as close as possible. The power dissipation must be small because the load is 100R, so the heat sink is not needed. The capacitor’s voltage must higher than the voltages used in the experiment. This circuit uses 40V, 1A Schottky diode or the 40V, 3A 1N5822 for heavier currents.

SIDAC Basic Operation

2010-10-23T01:36:00.001+07:00

Silicon Diode for Alternating Current, SIDAC, is a multilayer silicon semiconductor switch. This component is triggered by voltage and can be operated as bidirectional switch. Usually, this SIDAC is used in cheap high voltage power supply or ignition circuits. This is the figure shows SIDAC block construction, schematic symbol and geometric construction:

The SIDAC has leakage current(Idrm) less than 5 µA during off state. When the SIDAC receive a supply voltage greater than SIDAC Vbo, the device will turn to a negative resistance switching mode with characteristic like an avalanche diode. The SIDAC will turn on when it supplied with enough current(Is), it allows high current to flow. The magnitude of the current flow affect the voltage drop when the voltage accross the SIDAC. The SIDAC is still on as long as holding current is less than maximum value(150mA). The switching current (Is) is very near the holding current (Ih). A discharging small capacitor can generate current of 10A to 100A to primary or small, very high-voltage transformers for 10 µs to 20 µs when the SIDAC switches.

555 IC Linear Ramp (Sawtooth) Generator/Oscillator Circuit

2010-10-23T01:35:00.002+07:00

The Vc1 increases linearly when the pull-up resistor RA in the mono stable circuit is replaced with constant current source, generating a linear ramp. This is the figure that shown the linear ramp generating circuit and the generated linear ramp waveforms illustration;

Current source is created by PNP transistor Q1 and resistor R1, R2, and Re.

Ic= (Vcc-Ve)/Re

Ve= Vbe + (R2/(R1+R2))Vcc

For example, if Vcc=15V, RE=20k, R1=5kW, R2=10k, and VBE=0.7V, VE=0.7V+10V=10.7V, Ic=(15-10.7)/20k=0.215mA

The current flowing through capacitor C1 becomes a constant current generated by PNP transistor and resistor when the trigger starts in a timer configured as shown in figure below.

Hence, the Vc is linear function. The gradient S of the linear ramp function is defined as:

S= (Vp-p)/T

The Vp-p is the peak to peak voltage. The Vc comes out as follows is the electric charge amount accumulated in the capacitor is divided by the capacitance.

V= Q/C

The above equation divided on both sides by T gives us

V/T= (Q/T)/C

and may be simplified into the following equation.

S=I/C

In other words, we can obtained the gradient of the linear ramp function appearing across the capacitor by using the constant current flowing through the capacitor. The gradient of the ramp function at both ends of the capacitor is S = 0.215m/0.022? = 9.77V/ms if the constant current flow through the capacitor is 0.215mA and the capacitance is 0.02uF. [Circuit's schematic diagram source: Philips Semiconductors Application Notes]

Simple Telephone Ring Tone Generator Circuit

2010-09-14T22:45:00.000+07:00

This is the figure simple telephone ring tone generator circuit designed using only a few components. It produces simulated telephone ring tone and needs only DC voltage (4.5V DC to 12V DC). One may use this circuit in ordinary intercom or phone-type intercom. This is the figure of the circuit;

The sound is quite loud when this circuit is operated on +12V DC power supply. However, the volume of ring sound is adjustable. The commonly available 14-stage binary ripple counter with built-in oscillator (CMOS IC CD4060B) is used to generate three types of pulses, which are available from pin 1 (O11), pin 3 (O13), and pin 14 (O7), respectively. Preset VR1 is adjusted to obtain 0.3125Hz pulses (1.6- second ‘low’ followed by 1.6-second ‘high’) at pin 3 of IC1. At the same time, pulses available from pin 1 will be of 1.25 Hz (0.4-second ‘low’, 0.4-second ‘high’) and 20 Hz at pin 14. The three output pins of IC1 are connected to base terminals of transistors T1, T2, and T3 through resistors R1, R2, and R3, respectively.

Simple Single Cell 1.5V Hearing Aid Circuit

2010-09-14T22:43:00.000+07:00

This is a hearing aid circuit with 1.5v supply. This circuit is used to detect very faint sounds, then deliver the sounds to an 8 ohm earpiece. This circuit requires 1.5v input voltage, need only a single cell battery. This is the figure of the circuit;

This circuit can be assembled in a small board, or you can even do it without board. To assemble without board, you can connect every component leads each other and solder them. Align the component bodies and their leads to avoid shorts, secure with insulation tape, glue, or resin.

Simple Signal Injector Circuit

2010-09-14T22:41:00.002+07:00

This is a circuit for signal injector circuit that is important tool for troubleshooting your electronic circuits. As an example, this circuit can be used to test amplifier circuit. This is the figure of the circuit;

This circuit also a lot of harmonics. By connecting the ground clip to the 0v rail and move through each stage, starting at the speaker, the fault in an amplifier can be found. At each preceding stage, the volume will increase. This circuit can inject FM sound sections in TV’s and the IF stages of radios.

Simple Low Voltage Alarm Circuit

2010-08-26T20:27:00.000+07:00

This is a circuit for alarm circuit. This is a simple form circuit. This is the figure of the circuit;

This circuit can be used to monitor batteries and other volatile sources of current for problems. The circuit sounds an alarm and lights an LED, but can be interfaced to any number of other circuits for many different uses.
Part;
R1, R3 1K 1/4W Resistor
R2 5K Pot
U1 LM339 Voltage comparator IC
D1 1N5233B Zener Diode
D2 LED
BZ1 Piezo Buzzer
MISC Board, wire, socket for IC

Simple Servo Tester Circuit

2010-08-17T20:13:00.000+07:00

This is a circuit for a simple servo tester which will comprehensively test the capabilities of almost any modern servo. It has two pushbuttons, CENTRE and SWEEP and a potentiometer. This is the figure of the circuit;

CENTRE Does exactly that, centers the servo, afterwards the potentiometer determines position. SWEEP Sweeps the servo back and forth at a rate determined by the potentiometer setting. The PIC uses its internal timer to set up a constant frame duration of 20ms and the on/off ratio is set by the user.

Simple Optical Switch Circuit

2010-08-17T20:11:00.000+07:00

This is a circuit for optical switch that is used 555 timer IC. The IC is proved to be the most versatile and ubiquitous IC all over the world. This is a possible use: simple inverting schmitt trigger. This is the figure of the circuit;

When the phototransistor is stroke by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the photo trans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC). The amount of light that strike the photo trans necessary to bring his collector to VCC/3 is determined by the resistor (Vdrop = Icollector * R , so , if Vdrop= 2*VCC/3, the resistance needed to set the threshold on current is R=2*VCC/(Icollector*3)). High sensibility photo trans would need a smaller resistor, and weaker phototransistors higher value resistor, you can also use a trimmer to set the on threshold level with precision. The time of phototransistor isn't critical. The 555 has high current capability and can drive various devices, such as Bipolars, relays, bipolar + relays, mosfets, mosfets + totem pole , or give a logic output.

In case you need to trigger something when the gate is blocked (for example a burglar alarm, or a multistage coil gun) you need to invert the output, which is accomplished using a small bipolar transistor wired in an inverting setup (see pic) or swapping the positions of phototransistor with the resistor, so the voltage will drop under VCC/3 when blocked: The formula to determine the resistance to turn off at Icollector is R=VCC/(Icollector*3).

Simple Bass Booster Circuit

2010-08-17T20:08:00.000+07:00

This is a circuit for bass booster that is powered by an ordinary 9 volt transistor radio battery. This is the figure of the circuit;

The design of a Bass Booster Circuit using LM390. The LM390 Power Audio Amplifier is optimized for 6V, 7.5V, and 9V operation into low impedance loads. The booster connects between your instrument and its amplifier through two standard RCA Jacks.

Auto Heat Limiter Circuit for Soldering Iron

2010-08-17T20:00:00.000+07:00

Usually a soldering iron takes a couple of minutes to get adequately heated up to melt the solder, after which the heat generated is much above the requirement and is wasted. This is a design circuit for the solution of the problem. This is a heat limiter circuit that can be work automatically. This is the figure of the circuit;

Once the main is switched on, an approximate 15v drop of the positive half cycle across R5 is detected and supplied to Q1 (SL100 or D313), which acts as a voltage regulator. Zener diode D2 together with diode D3 (yellow LED) stabilizes the emitter voltage of Q1 at 13.2Vdc, which is then delivered to the relay circuit built around Q2 and C3. Capacitor C3 charges through the base-emitter path of Q2 and causes the relay to actuate, which in turn allows both the half cycles of the AC mains to flow through diode D6 and R5 to the load to heat it up at a normal rate.

After a certain lapse of time (about 2 minutes preset) C3 saturates and Q2 stops conducting through the relay, thus switching on series diode D5 to allow only half of the Ac cycle through the load. After switching off the system, C3 discharges very slowly through R2 and R3. Before C3 gets completely discharged, if the power is switched on again, C3 takes a shorter time to reach the saturation level, thus switching series diode D5 much earlier than the preset time to prevent double heating of the load.

However, if the circuit is switched on only after a few seconds of switching off, C3 gets no time to discharge and the relay does not actuate at all. Moreover, if the relay circuit fails due to any reason and Q2 does not conduct, no harm is done to the load because in that case D5 remains in series with it. Thus the circuit offers complete protection to the load.

As stated earlier, the given value of C3 gives a delay of 2 minutes. However, a 1000mfd capacitor can also be used to produce a 4.5-minute delay. R5 maintains a drop of about 15V across itself.

Simple Mini Variable Power Supply Circuit

2010-08-15T07:09:00.000+07:00

This is a circuit for variable power supply. This circuit is a simple form circuit. This is the figure of the circuit;

T1 steps down AC voltage from 115VAC (or 220VAC) to about 8VAC and is then rectified via bridge rectifier BR1 to about 11.52Vdc. C1 filters off the AC ripple. If you find the circuit output too noisy add another electrolytic capacitor over the output terminals. Value can be between 10 and 100uF/25V. The output voltage is variable with the 10K-potentiometer while keeping the current constant.

Simple Electronic Drum Synthesizer Circuit

2010-08-15T07:07:00.000+07:00

This is a circuit for electronic drum synthesizer. This circuit is consists of two “twin-T” oscillators set to a point below oscillation. To set the circuit into oscillation, we can touch the Touch Pad. This is the figure of the circuit;

By touching the pads in different ways and a whole range of effects are available will produce different effects. Before oscillation, the two 25k pots are adjusted to a point. We can produce a drum roll by shifting a finger rapidly across adjacent ground and drum pads.

Simple Discrete Logic Probe

2010-08-15T07:06:00.000+07:00

This is a design circuit diagram for logic probe circuit. Logic probe is used to determine if a point in a circuit has high or low state when the circuit is in operation. This is the figure of the circuit;

When the probe is not touching any circuitry, this circuit consumes no current. It can happen because the voltage across the red LED and base-emitter junction of the 2N3904 plus voltage across the green LED, the base-emitter junction of the 2N3906 is approx 1.7v + 0.6v+2.1v + 0.6v = 5v. This voltage is greater than the supply voltage. the red LED will illuminate, when the circuit detects a HIGH (above 2.3v) and When detects a LOW is detected, 2N3906 will turn on and the green LED illuminates.

Simple 1N4007 Silicon Diode Laser Power Supply Circuit

2010-08-15T07:04:00.000+07:00

This is a circuit power supply. This circuit is design for laser. This is the figure of the circuit;

If you have ever worked with lasers, you know how fun and interesting it can be, you also know how expensive it can be. The high voltage power supplies for the laser tubes are often more expensive then the tubes themselves. This supply can be built with commmon parts, most of which you probably already have in your junk box. The secret is the transformer used. It is a common 9V 1A unit, connected backwards for step up.

Simple Single Pole Active Filter Circuit

2010-07-31T09:20:00.001+07:00

This circuit is a design circuit for tool calculated the required resistor and capacitor values for a single pole active filter. The routine assumes the input signal swing will be differential peak swing of 80%*VDD. Given the SNR, and the swing the resistor and capacitors can be sized. This is a simple form circuit.

This is the figure of the circuit;

Part and characteristic;

Inputs
Voltage Gain V/V
3dB bandwidth Hz
Signal to Noise Ratio dB
Supply Voltage V

Outputs
R1 kΩ
Rf kΩ
Cf pf

Simple LED Light Flasher Circuit

2010-07-19T13:23:00.001+07:00

This is a simple LED flasher project that uses a CMOS 74C04 Integrated Circuit to alternately ON and OFF two LEDs that are connected in parallel. The Hex inverter MM74C04 from Fairchild Semiconductor has a wide operating power supply voltage range from 3V to 15V DC. This is the figure of the circuit;

It has a typical low power consumption of 10nW/package and has high noise immunity. It is back to back compatible with the standard 74 logic family which is freely available in the market. All its inputs have diode clamps to VCC and GND which protect them from damage due to electrostatic discharge. The schematic above shows the simple configuration of the project. It uses two inverters U1A and U1B to form an oscillator configuration where the frequency of the oscillation is given by :

f = 1/[1.4RC]
= 1/[1.4(10 M Ohm)(0.1uF)]
= 0.7 Hz

The square wave frequency of 0.7 Hz is used to feed the input of U1D which is used as a buffer circuit. At the same time, the other inverter U1C gets its input from pins 2 and 3 of U1. With this configuration, when U1D output is high, U1C output will be low and vice versa. In this way when LED1 is ON, LED2 will be OFF and this will alternate at a frequency of 0.7Hz.
The current that goes through the LED is given by:

I = (9V-7V)/510 ohm
= 14mA

It is assumed that the voltage drop across each diode is 2V when it turns ON. One can experiment with the oscillation frequency by changing the values of R1, R2, R3, and C1. The brightness of the LEDs can also be changed by changing the values of the resistor R4. However, always ensure that the current through the LEDs is not exceeded or else the LEDs will be damaged.

Simple TPS108x Versatile Boost Converter

2010-07-13T07:19:00.000+07:00

This is a design circuit of the Versatile Boost Converter circuit using TPS108x. The TPS1081 has chosen because it is suitable for application that requires up to 20 V and 100 mA to drive each column of a passive-matrix OLED (PMOLED). The TPS61080 is suitable for application that requires less than 10 V and only tens of milliamps per column for the active-matrix OLED (AMOLED). This is the figure of the circuit;

The TPS61081 and TPS61080 require input voltages as low as 2.5 V and have adjustable outputs of up to 27 V. Current limit rating of the integrated power switches is the different of The TPS61081 and TPS61080 (typically 1.3 A and 0.5 A, respectively).

The TPS6108x boost converters have constant pulse-width-modulation (PWM) frequency and a traditional current-mode-control scheme for low-noise operation. Besides that, it has additional feature such as n adjustable reference voltage, high efficiency and redundant protection circuits—all of which make the TPS6108x ideal for boosting the 3.6-V Li-ion battery voltage used in most portable applications. The converter can also be used to power higher voltage application such as camera flashlights, OLED displays, WLED backlights and thin film-transistor (TFT) LCDs.

The switching frequency of the converter can be configured to 600 kHz for light-load efficiency or 1.2 MHz for smaller, external components. The 3 × 3-mm QFN package can enable an extremely small boost converter for a wide variety of applications because it has internal power switches, integrated feedback compensation and fast PWM switching. For example, a 24- or 12-V or industrial power rail from a 5-or 3.3-V bus.

[Circuit Source: Texas Instruments Application Note]

Simple Code Lock Circuit

2010-07-13T07:18:00.001+07:00

This is Simple Code Lock circuit. This circuit will turn on a relay when the 8-way DIP switches receives the correct code. This is the figure of the circuit;

There are two different types of DIP, they are piano-key DIP sw and 8-way DIP sw. This circuit will not draw the current if the switch is kept off. This circuit can give 256 different combination because the combination is in binary. So it would be very difficult for a burglar to keep up with the settings of the switches.

[Schematic circuit source: talkingelectronics.com]

Simple Broken Charger Circuit

2010-07-13T07:16:00.001+07:00

This circuit can be useful to detect if the load of any battery charger or plug-in adaptor supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device. The circuit can safely operate over a 3 to 15V range and 1A max. current, provided the supply voltage is about one volt higher than the voltage required by the load. This circuit is the figure of the circuit;

The circuit is inserted between the supply and the load, therefore, until a trickle-charging current of at least 100µA is flowing towards the load, D1 and D2 will conduct. The forward voltage drop (about 1V) available across the Diodes, drives Q2 into conduction and, consequently, Q1 will be cut-off. If no appreciable load is connected across the circuit's output, Q2 will become cut-off, Q1 will conduct and the Piezo-sounder will beep.

Parts:
R1______________10K 1/4W Resistor
R2_______________1K 1/4W Resistor
R3_______________1K 1/4W Resistor (Optional, see Notes)

D1,D2________1N4007 1000V 1A Diodes
D3______________LED Red (Optional, see Notes)

Q1,Q2_________BC557 45V 100mA PNP Transistors

Simple AM Signal Catcher Circuit

2010-07-13T07:14:00.001+07:00

This is a very simple design and easy to build circuit of AM modulation monitoring for HAM transmitters. This is the figure of the circuit;

This circuit is only build by diode and capacitor. You don't have to make any connection with the transmitter only you have to do is that place the coil L1 near the final tank of antenna matching inductor until you hear the signal in the headphones. The circuit is very simple containing only four parts. L1 = coil 3 turns on 1.5 inch diameter former use any guage wire.

Simple Wideband SWR Meter Circuit

2010-06-24T10:06:00.001+07:00

This is a circuit of Wideband SWR Meter. This circuit is used as a test instrument. To use this circuit, connect the meter, take the necessary readings, then disconnect. The meter should not be left in the line permanently because it draws up 3/4 of the transmitted power, and a similar part of a received signal. This circuit uses Three pairs of 100 Ohm resistors those are combined in a bridge circuit, with the load as the fourth resistor. The diode, D1, is used to rectify a sample of the input signal, while D2 used to rectify the differential voltage across the bridge. So, the square root of reflected power can be achieved. This is the figure of the circuit;

The two output voltages of the circuit are applied to two simple galvanometers and to a ganged potentiometer. Besides that, this output voltage can be applied to digital displays, microprocessors, etc. A 5Vrms RF signal is applied to the input and A 50 Ohm load is connected to the antenna side. So 1/2W will across 50 Ohm. D1 provides 3.5V DC because At the anode of D1 have 2.5Vrms, or 3.5V peak. D2 will not produce any DC output because it see exactly the same RF voltage at both sides, and in the same phases. The meter indicate a 1:1 SWR when The forward meter move, while the reflected signal meter will stay at zero. The transmitter will indicate 1:1 SWR too because it see 2 times 100 Ohm in parallel, or 50 Ohm. while the remaining quarter gets delivered to the antenna, One quarter of the power will be dissipated in each of the resistor pairs.

When the extreme condition occurs like the load was disconnected, so the circuit has infinite SWR. D1 see half of the input voltage, and no voltage drop across them, and there is now no current in R1/R2. D2 produces the same rectified output as D1 does because it see “the other half” of the input voltage. So the meter indicate all power is being reflected because both meters deflect by the same amount, and the SWR is infinite. The transmitter indicate a 2:1 SWR because it see 100 Ohm load, far away from causing danger to any transmitter.
[Circuit source: Homo Ludens Electronicus]

Simple Low Distortion Oscillator Circuit

2010-06-24T10:04:00.000+07:00

This is a simple design circuit with very low harmonic distortion, 2N4416 JFET is suitable to smoothly oscillate in a circuit. On application where low harmonic content is required for a good mixer circuit, JFET local oscillator is very good. This is the figure of the low distortion oscillator circuit;

This is the 20 MHz Oscillator Values
· C1 = 700 pF L1 = 1.3 mH
· C2 = 75 pF L2 = 10T 3/8″ DIA 3/4″ LONG
· VDD = 16V ID = 1 mA
20 MHz OSCILLATOR PERFORMANCE
· LOW DISTORTION 20 MHz OSC.
· 2ND HARMONIC -60 dB
· 3RD HARMONIC > -70 dB

[Source: National Semiconductor Application Note]

Simple DC or AC Voltage Indicator Circuit

2010-06-24T10:03:00.002+07:00

This circuit is a circuit diagram is not a novelty, but it proved so useful, simple and cheap that it is worth building. When the positive (Red) probe is connected to a DC positive voltage and the Black probe to the negative, the Red LED will illuminate. This is the figure of the circuit;

Reversing polarities the Green LED will illuminate. Connecting the probes to an AC source both LEDs will go on. The bulb limits the LEDs current to 40mA @ 220V AC and its filament starts illuminating from about 30V, shining more brightly as voltage increases. Therefore, due to the bulb filament behavior, any voltage in the 1.8 to 230V range can be detected without changing component values.

Parts:
P1 = Red Probe
P2 = Black Probe
D1 = 5 or 3mm. Red LED
D2 = 5 or 3mm. Green LED
LP = 1220V 6W Filament Lamp Bulb
Source :extremecircuits.blogspot.com

Simple Programmable Voltage Regulator Using L200 IC

2010-06-08T08:25:00.003+07:00

This is a simple programmable voltage regulator circuit. With this circuit we can generate a voltage according to our wishes. This circuit is based on L200 IC. This is the figure of the circuit;

Potentiometer R2 is used to fix the output voltage Vo. Following equation show value of the output voltage:

Vo=Vref (1+(R2/R1))

We can obtain a wide range of fixed output voltage by substituting the potentiometer with a fixed resistor and choosing suitable values for R2 and R1.

[Circuit source: SGS-Thomson Application Note]

Simple Precision Current Sink Circuit

2010-06-08T08:19:00.003+07:00

This a a simple circuit for precision current sink. This circuit uses two kinds of transistor, 2N2219 bipolar transistor and 2N3069 JFET because both of them have inherently high output impedance. This is th figure of the circuit;

To provide feedback to the LM101 op amp, this circuit uses R1 as a current sensing resistor. The true current sink nature of this circuit is enhanced because the op amp provides a large amount of loop gain for negative feedback.

The output current is given by :

Io = Vin/R1

with Vin > 0 V

The 2N2219 and the 10K resistor may be eliminated, for small current values, if the JFET’s source is connected to R1.

[Source: National Semiconductor Application Note]

Simple Air Flow Detector Circuit

2010-06-08T08:13:00.002+07:00

This is a design of simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. This is the figure of the circuit;

As air flows over the filament it cools down, thus lowering it's resistance. A comparator is used to detect this difference and light an LED. With a few changes, the circuit can be connected to a meter or ADC to provide an estimations on the amount of air flow.

Part;

R1 100 Ohm 1/4W Resistor

R2 470 Ohm 1/4W Resistor

R3 10k 1/4W Resistor

R4 100K 1/4W Resistor

R5 1K 1/4W Resistor

C1 47uF Electrolytic Capacitor

U1 78L05 Voltage Regulator

U2 LM339 Op Amp

L1 #47 Incandescent lamp with glass removed (See "Notes")

D1 LED

Simple Air Flow Detector Circuit

2010-05-15T18:50:00.001+07:00

This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. This circuit is using LM332 as main components. This is the figure of the circuit;

A comparator is used to detect this difference and light an LED. With a few changes, the circuit can be connected to a meter or ADC to provide an estimation on the amount of air flow.

Part:

R1 1 100 Ohm 1/4W Resistor

R2 1 470 Ohm 1/4W Resistor

R3 1 10k 1/4W Resistor

R4 1 100K 1/4W Resistor

R5 1 1K 1/4W Resistor

C1 1 47uF Electrolytic Capacitor

U1 1 78L05 Voltage Regulator

U2 1 LM339 Op Amp

L1 1 #47 Incandescent lamp with glass removed (See "Notes")

D1 1 LED

Simple Overture 30 Watt Audio Power Amplifier with Mute and Standby Modes

2010-05-14T20:18:00.001+07:00

This is a circuit for a audio power amplifier that is based on single op amp LM4700. This circuit is a basic design. This is the figure of the circuit;

The LM4700 is an audio power amplifier capable of delivering typically 30W of continuous average output power into an 8 load with less than 0.1% THD+N. The LM4700 has an independent smooth transition fade-in/out mute and a power conserving standby mode which can be controlled by external logic. The performance of the LM4700, utilizing its Self Peak Instantaneous Temperature (°Ke) (SPiKe™) protection circuitry, places it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area (SOA). SPiKe protection means that these parts are completely safeguarded at the output against overvoltage, under voltage, overloads, including thermal runaway and instantaneous temperature peaks.