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Tuesday, November 24, 2009

Simple Voltage Inverter Circuit

This is a simple design for inverter that produces voltage. This circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components. This is the figure of the 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. A zener diode may also be used to regulate the output voltage. For better regulation, a 79LOxx series regulator can be used.

R1 24K 1/4 Watt Resistor
R2 56K 1/4 Watt Resistor
C1 3300pF 25V Ceramic Capacitor
C2 47uF 25V Electrolytic Capacitor
C3 10uF 25V Electrolytic Capacitor
C4 100uF 25V Electrolytic Capacitor
D1, D2 1N4148 Silicon Diode
U1 555 Timer
MISC Wire, Board

Simple Voltage Detector

This is a simple design for sensing the over voltage. Sensing is done by zener diode. This is the figure of the circuit.

When the zener diode conducts, the gate of the SCR is turned on and causes the SCR to short which blows the 15 amp fuse and shuts off the output voltage. A 2N6399 was used for the SCR in the prototype but any suitable SCR can be used. While over voltage protection is a good idea, it should not be considered a substitute for large heat sinks.

Simple Micro Power Pulse Generator

This is a simple design for pulse generator. This circuit is based on op amp. This is the figure of the circuit.

This circuit produces clean logic pulses while drawing very low current. This circuit is designed to produce short 2mS pulses at a rate of one per second while drawing only 1 micro amplifier from a 9 volt battery.

Simple 6V to 12V Converter Circuit

This circuit is an inverter actually. This circuit is not converter, but it is say as converter cause convert voltage from low to high. This inverter circuit can provide up to 800mA of 12V power from a 6V supply. For example, you could run 12V car accessories in a 6V of the car. The circuit is simple, about 75% efficient and quite useful. This is the figure of the circuit.

This circuit is work based on transistor. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents. You can use a larger value for C3 to provide better filtering. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

R1, R4 2.2K 1/4W Resistor
R2, R3 4.7K 1/4W Resistor
R5 1K 1/4W Resistor
R6 1.5K 1/4W Resistor
R7 33K 1/4W Resistor
R8 10K 1/4W Resistor
C1,C2 0.1uF Ceramic Disc Capacitor
C3 470uF 25V Electrolytic Capcitor
D1 1N914 Diode
D2 1N4004 Diode
D3 12V 400mW Zener Diode
Q1, Q2, Q4 BC547 NPN Transistor
Q3 BD679 NPN Transistor
L1 See Notes MISC1Heatsink for Q3, Binding Posts (for Input / Output), Wire, Board

Wednesday, November 11, 2009

Simple Surround Sound Decoder

This is a design for surround sound decoder. This circuit works by allowing the rear speakers to reproduce only the difference signal between the left and right outputs. This is the figure of the circuit.

Op amp U1A is connected as a subtracting amplifier. Should the same signal be applied to both inputs, the output is zero. As a result, it will remove all common information from the stereo signal, and reproduce only the difference signal - in exactly the same way as the original Hafler design. U1B is a simple summing amplifier, and the output contains all the information from both the left and right channels. A possibility that springs to mind is that we could then subtract the difference information from this output, so that only material that is absolutely common to both channels would be reproduced. Would this improve the performance to the extent that the extra circuitry is warranted? I tend to doubt it, but will look into this further.

Simple PLL FM Demodulator

This is a circuit about PLL system that can be used to implement an FM demodulator. Since the VCO output tracks the FM signal, and the VCO input voltage is proportional to the VCO output frequency, then the VCO input will be equal to the demodulated signal. This is the figure of the circuit.

For this example, an FM signal consisting of a 10-kHz carrier frequency was modulated by a 400-Hz audio signal. The schematic diagram shows the connections of the CD4046B as an FM demodulator. The total FM signal amplitude is 500 mV, therefore, the signal must be ac coupled to the signal input (terminal 14). Phase comparator I is used for this application because a PLL system with a center frequency equal to the FM carrier frequency is needed. Phase comparator I lends itself to this application also because of its high signal-input-noise-rejection characteristics.

Simple Pierce XTAL Oscillator Circuit

This circuit is conventional “Pierce” type oscillator that uses a JFET. The circuit uses fundamental mode crystals. It has decent performance and reliability if we use a low noise JFET. This is the figure of the circuit.

The feedback is controlled by the C1 Capacitance from drain to ground. Adjusting the frequency can be done by adjusting a shunt capacitance C2 across the crystal. The crystal works in parallel mode. This circuit is suitable where some crystals should be switched in and out to select the frequency, as there’s no tuning required.

Simple Current Loop Transmitter Circuit for Temperature Sensor

This circuit provide current loop transmitter for temperature sensor. Current loop interface has been widely used in industrial environment because it’s robustness. This is the figure of the circuit.

The temperature measurement is done by LM35 temperature sensor chip. You can use general silicone diode such as 1N4001. The current controller function is done by LM317 current/voltage regulator. This circuit will draw a consistent current proportional to the temperature being measured, regardless the supply voltage variation caused by noise or long wire’s temperature-dependent resistance variation.

Simple Automatic Nicad Battery Charger

Many cheap battery chargers usually assume that charging the battery slowly is OK although the battery is already full of charges. All they do is usually charging the battery with constant current no matter if the battery is almost completely discharged or has been fully charged. Off course the battery wouldn’t be damaged immediately after few charging cycles, but actually they’re damaged slowly and the life time can’t be maximized. This is one of solution for the problem above.

This circuit is automated that you don’t have to manually set the alarm timer to wake you up when your battery has been fully charged so you can unplug the charger to prevent overcharging. This battery sense the voltage while charging the battery, and automatically stop the charging when it’s fully charged. This is the figure of the circuit.

To set the R8, turn the variable resistor R8 to its maximum value (highest resistance), connect a fully charged Nicad battery (about 1.44V) to the battery terminal. Press and release the start push button, and make sure the LED D1 is turned on after releasing the start push button. Now turn the R8 slowly toward its minimum value and stop turning exactly when the LED D1 turned off. Now your automatic Nicad battery charger is ready. Place a discharged battery and press the start button, the D1 LED will turn on to indicate that the charging is in progress. LED D1 will turn off after the battery has been fully charged. To provide multiple battery charging, make few more similar circuits shown in the dashed line box, and you can charge up to ten Nicad battery (50 mA charging current per battery) using 1 Ampere 9-12 volts transformer.

Simple Audio Mixer Using FET

This is a simple project circuit for mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consume very little power. This is the figure of the circuit.

This circuit is based on or built by FET 2N3819. The circuit can be powered by a single 9 volt battery. As many or as few channels as are required can be added to the mixer. A shielded case is probably needed to reduce hum and help stop oscillations.

R1, R3 10K Pot
R2, R4 100K 1/4 W Resistor
R5 6.8K 1/4 W Resistor
C1, C2, C3 0.1uF Capacitor
Q1 2N3819 Junction FET
MISC Wire, Shielded (Metal) Case, Phone or Other Plug For Output

Simple Voltage Regulator using LM338

This circuit is a circuit diagram power supply. Circuit diagram works on voltage +13.8 V 5A with electric currents. This circuit controlled by the LM338 IC. This is the figure of the circuit.

Many times we need a supply of relatively strong in the framework we provide a variety of equipment with + 13.8V, as transceivers CB, cargo lead-acid batteries, and others known to use the circuit capable of providing complete in his exit, when This continuously operating 5A and 12A peak current. Not only need a few external components. Setting the voltage at + 13.8V to the trimmer TR1, (multiturn). The IC1 LM338 must in each case is placed on one suitable heat sink, which both supported by one fan. All the connections by the circuit become with big cross-section cable, because the current through from within their already high enough.

R1=270R 1/4W 2%
TR1=4k7 (Multiturn)
C1=10000uF 40V
C2-3=100 nF 100V Polyester
C4-5=10uF 25V
D1-2=1N4002 (1A/100V)
B1=25A Bridge Rectifier
T1=220Vac/15VAC – 8A Mains Transformer
S1=2 Pole Single Throw Mains Switch
F1=250mA Fuse

Saturday, November 7, 2009

Simple Stepper Motor Controller Circuit

This is a circuit for motor stepper controller. A stepper motor controller is needed to run a stepper motor, since a stepper motor cannot work by just connecting it to a power supply. To program a stepper motor to make a complex movement, we usually need a micro controller. This is the figure of the circuit.

This stepper motor controller circuit is still need an external input. If we look at the table, the input pattern is similar to a 2 bits binary counter. If you have an up-down binary counter, then you get a forward-reverse control for your stepper motor.

Simple Open Loop Fast Peak Detector Circuit Using Op Amp

This is a design for peak detector. This circuit is a fast peak detector similar but faster than previous peak detector, can be implemented using open loop configuration. This circuit is based on op amp LT1190. This is the figure of the circuit.

In this design, D1 is the detector diode and D2 is a level shifting or compensating diode. A load resistor RL is connected to – 5V and an identical bias resistor, RB, is used to bias the compensating diode. This equal value resistor is RL and RB makes sure that the diode drops are equal. Low values of RB and RL (1k to 10k) yield in fast response, at the expense of poor low frequency accuracy. High values of RB and RL provide good low frequency accuracy but cause the amplifier to slew rate limit, resulting in poor high frequency accuracy. A solution can be made by adding a feedback capacitor CFB, which improve the negative slew rate on the (–) input. We can expect under 15% amplitude error for 2Vpp-6Vpp input at 20MHz, much faster than closed loop design. [Circuit source: Linear Technologies, Inc].

Simple Light Sensor Circuit

This is a design sensor circuit that can be used for sensing the light. This circuit is using a comparator LM311. This circuit is very simple design. This is the figure of the circuit.

This comparator is powered from 12 V DC supply and does not require negative supply to work efficiently. Feedback given to the comparator provides some hysteresis and the potentiometer allows to adjustment the sensitivity of the detector for darkness.

R1 = 1K
R2 = 100K
R3 = 10K
R4 = 2K
D2 = 1N4001
U1 = LM311

Simple AC Powered LED Circuit

This is a simple diagram for LED indicator circuit which is the resilience of the nature of high light emitting diode (LED) make it suitable for ON / OFF indicator applications. Due to limitations on the operating voltage is low, the LEDs are usually applied to low voltage applications. Fortunately, there is a simple method to implement the LED indicator for high voltage power line: reactance of the capacitor can be used to restrict at any time without dissipating power, this is because the voltage at the capacitor 90 degrees different from that now. This is the figure of the circuit.

In the picture above the zener diode used to limit the voltage and allows current to flow in reverse direction on the cycle where the current flow can’t flow through the LED. Without this zener, which it will now actually stop flowing since the capacitor block is now flowing in one direction only. Capacitor will determine the current setting options, approximately 4 mA to 20 mA and 100nF to 470nF.