Simple LED Bike Light Schematic

We know flashing LED lights from the high street shop. But, they were often gave me trouble with flat batteries and lights that fell off. In this case, we make a better one idea using another front wheel, one which has a dynamo already built in the hub. This supplied a nice sine wave of 30 Vpp (at no load). With this knowledge I designed a simple power supply. The transistors that are used are type BD911. These are a bit of an overkill, but there were plenty of these at my school, so that is why I used them. Something a little smaller will also work. The power supply is connected to an astable multi-vibrator. This alternately drives the front light and the rear light. This is the figure of the circuit.

Simple 220V Soft Start Schematic Circuit

Here’s In particular, the power supply with a high value capacitor is used in SMPS circuits in the 220V soft start circuits, as in most of them, this circuit has a simple structure and is designed to operate by directly regulating 220v without transformer. Here’s a figure of the schematic.

Current Source for Grounded Load Circuit

This is a design for a current source (as opposed to current sink) for driving a grounded load can be a bit awkward. Admitedly the suggested circuit cheats a little in that the load is tied to virtual grounded, so it’s still potentially useful. This is the figure of the circuit

Two control loops are involved here:

Opamp A1 maintains the ‘cold’ end of the load at virtual earth and

A2 sets a current I = –V1/R1, which also flows through the load R_L.

DS18B20 Temperature Sensor Circuit

This is a sensor to detect the temperature. This sensor can be programmable to sensor device. This device can operate using power supply 3V to 5V VDC and have temperature range -55°C to +125°C with accuracy ±0.5ºC. In programmable system, this device has output Resolution: 9-bit to 12-bit and unique 64-bit address enables multiplexing. This sensor is a waterproof sensor. This is the figure schematic for the sensor using DS18B20.

Simple AVR ISP Circuit

Here’s a design circuit for simplest AVR ISP circuit is shown here, with some notes. Ground and VCC must be connected to programmer, either to power programmer or to provide a reference voltage for lower voltage circuits. This is the figure of the circuit;

Most AVR microcontrollers use MOSI, MISO and SCK SPI pins for programming, but some such as ATmega128 use SCK and then UART TX and RX pins instead. The capacitor connected between Reset and Ground, and the resistor from Reset to Vcc should be fitted to give a slight delay to allow AVR to power up properly. These values are not critical, but if they are too large then the ISP programmer will need to be slowed down. The programming lines (SCK, MISO and MOSI) are best left just for programming, but if these pins must be used by the application, then resistors should be used to isolate the application circuitry, typically 4K7. This is especially important if TXD/RXD are used for programming, as UART chips tend to hold the lines. This should be fine for SPI or UART use or where pins are inputs but if you have to use these lines for higher current, then a multiplexer circuit may be needed, see STK200 schematics. Capacitors on the programming lines can cause problems, especially on SCK. If they have to be fitted, then they should be below 10nF and fitted as close as possible to AVR microcontroller pins. Some low cost programmers will have problems with even a 10nF capacitor on SCK or MOSI, so smaller is better.

Simple Electrification Circuit Unit

Here’s a design circuit that is intended for carrying out harmless experiments with high-voltage pulses and functions in a similar way as an electrified fence generator. The p.r.f. (pulse repetition frequency) is determined by the time constant of network R1-C3 in the feedback loop of op amp IC1a: with values as specified, it is about 0.5 Hz. The stage following the op amp, IC1b, converts the rectangular signal into narrow pulses. Differentiating network R2-C4, in conjunction with the switching threshold of the Schmitt trigger inputs of IC1b, determines the pulse period, which here is about 1.5 ms. The output of IC1b is linked directly to the gate of thyristor THR1, so that this device is triggered by the pulses. Here’s the figure of the schematic diagram;

The requisite high voltage is generated with the aid of a small mains transformer, whose secondary winding is here used as the primary. This winding, in conjunction with C2, forms a resonant circuit. Capacitor C3 is charged to the supply voltage (12 V) via R3.When a pulse output by IC1b triggers the thyristor, the capacitor is discharged via the secondary winding. The energy stored in the capacitor is, however, not lost, but is stored in the magnetic field produced by the transformer when current flows through it. When the capacitor is discharged, the current ceases, whereupon the magnetic field collapses. This induces a counter e.m.f. in the transformer winding which opposes the voltage earlier applied to the transformer. This means that the direction of the current remains the same. However, capacitor C2 is now charged in the opposite sense, so that the potential across it is negative. When the magnetic field of the transformer has returned the stored energy to the capacitor, the direction of the current reverses, and the negatively charged capacitor is discharged via D1 and the secondary winding of the transformer. As soon as the capacitor begins to be discharged, there is no current through the thyristor, which therefore switches off. When C2 is discharged further, diode D1 is reverse-biased, so that the current loop to the transformer is broken, whereupon the capacitor is charged to 12 V again via R3. At the next pulse from IC1b, this process repeats itself.

Tilt Sensor Alarm Circuit

This is a design for simple circuit of the tilt sensor alarm presented here can be fabricated using readily available inexpensive components. The circuit is a true transistor based design. Home made Tilt sensor for this circuit is an ordinary little glass/plastic bottle with two metal needles inserted through its cap, and a small quantity of water inside. A 9V alkaline battery is enough for powering the whole circuit. Here’s the figure of the schematic circuit;

In this figure shows that this circuit is based on two transistor as main control. There are BC 557 and BC 547. Usually, transistor T1 is in inactive state. When the sensor assembly is tilted, both needles inside the sensor (bottle) are short circuited by the water and a positive voltage is available at the base of T1 and it becomes active. Activation of T1 causes the activation of next transistors T2 and T3. After this, T2 supplies constant bias for T1 to make it latched and T3 triggers the SCR(T4) which in turn energizes the active piezo-sounder(BZ1). Once activated the circuit can be deactivated by depressing the power/reset switch S1. Preset pot P1 is deliberately added here to adjust the circuit sensitivity. This may become necessary if you are trying a different (readymade) tilt sensor. Similar, SCR(T4) and piezo sounder (BZ1) may be replaced with near equivalent parts. Resistor R3 (100-150 Ohm) is optional.

Simple Temperature Relay Circuit

This is a design circuit for temperature relay that can be used to signal a fire or set point for temperature monitoring function. You need to adjust P1 so that T1′s base voltage is 0.5V smaller than the emitter voltage at a temperature a little bit lower than the desired triggering (switching) temperature. This is the figure of the schematic circuit;

If the temperature increases then T1 and T2 start conducting and the relay is closed (ON). If you want to use it as a cold relay or to signal an inferior temperature limit, then Th1 and P1 change places. After the relay is triggering you need to open switch S1 in order to stop the circuit. The nominal value of P1 must be chosen according to the used NTC thermistor and the switching temperature to be adjusted.

220V Power Line Interface Circuit

Here’s a design circuit for simple 220V power interface is intended as an interface for monitoring electric equipments and devices using a computer. The interface only senses whether the device being monitored is turned on or off. The most important aspect of the circuit is the galvanic isolation between the AC main line being monitored and the interface to the computer. This is done with the use of the opto coupler IC TIL111 but a suitable replacement can be used too. This is the figure of the circuit;

In this circuit, to avoid having to modify the circuit for each device being monitored, the circuit monitors the device’s AC power line directly. The resistor R1 lets a current of around 0.5 mA through the opto coupler LED. The other half of the current is rectified through the diode D1. It is obvious that the current to the opto coupler LED is half wave rectified. This means that the phototransistor part of the opto coupler receives only light impulses of around 100uA. The capacitor C1 filters out the current pulsation and maintains a smooth output current. In case the current pulsation is needed, just remove C1.

Adjustable Regulator Circuit Using TL431

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

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

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

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

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.