## 12 to 5 volt Converter Circuit (for cars)

This 12 to 5 volt converter circuit is very useful. It can be used to connect 5 volt electronic devices in a car with a 12 volt battery. (Automotive lead-acid batteries can be up to 13.7 volts).

## Dual polarity Variable Power Supply (+15V / -15V) max

Dual polarity variable power supply (+/- 15 volts). Voltage source with a maximum amplitude of +/- 15 volts and a current of up to 1.5 amps.

## 4 Amp Variable Power Supply Using the LM317

This variable power supply using an LM317 and a boost transistor can be useful when we need more current than the 1.5 amps that an LM317 can provide.

## 12V 1A Power Supply Circuit

This 12V 1A power supply using zener diode and transistors allows us to obtain an output of approximately 11.4 volts with a very small percentage variation for a wide variety of loads.

## Variable Dummy Load for Power Supply Testing

Variable Dummy Load for Power Supply Testing. How to test a voltage source to know if it is good or not?. What is the percentage regulation?.

## 15V Power Source ON delay circuit

15V power source ON delay using LM317. This circuit uses the LM317 voltage regulator. It also uses a transistor and an a electrolytic capacitor

## 9VDC Power Supply using Zener and Transistor

9VDC Power Supply using Zener diode and Transistor

This Power source can be used to power circuits or electronic devices that would normally use a 9 volt battery, saving us the cost of the battery while being used at home.

## Transistor – Zener Voltage regulator circuit

Transistor – Zener diode Voltage regulator circuit. This circuit delivers an output voltage established by the voltage of the zener diode less 0.7 volts

## 12V to -12V DC converter circuit using 555

12 VDC to -12 VDC converter circuit with a 555 IC.

This 12 VDC to -12 VDC converter circuit gives -12VDC (negative 12 volts) from a power source of + 12VDC (positive 12 volts), with very few components.

## 4 Amp Variable Power Supply with 3 LM317

4 Amp Variable Power Supply with 3 LM317

4 Amp Variable Power Supply with 3 LM317 voltage regulators and a LM308 precision operational amplifier. Output voltage from 1.25 to 30 volts.

## LM350 Adjustable Voltage Regulator (Variable Power Supply)

LM350 Adjustable Voltage Regulator (Variable Power Supply)

This variable power supply uses the LM350 adjustable voltage regulator and can deliver 1.25 to 16 volts and a maximum current of 3 amps.

## 1.5 v Joule Thief Circuit with no Toroid Coil

1.5 v Joule Thief Circuit with no Toroid Coil

This 1.5 V Joule Thief circuit can turn ON one LED. The circuit do not use a toroid coil but it is possible to turn on a common red, green or yellow LED

## 12V to 9V DC Converter Circuit Diagram (PCB)

12V to 9V DC Converter Circuit Diagram (PCB)

This 12V to 9V DC converter is very useful for powering 9V DC devices in a car that uses 12V battery. The maximum current consumption allowed by this circuit is 0.8 amps.

## 20 Amp Variable Power Supply using LM317

20 Amp Variable Power Supply using LM317

20 Amp Variable Power Supply with an output voltage from 1.5 to 15 volts using the LM317 regulator and 4 2N3055 power transistors to amplify the current capacity

## 12V to 24V Converter Circuit

12v to 24v converter

This 12VDC to 24VDC step up converter is very useful to power devices that run on 24 VDC when we have a 12VDC voltage source as it could be a car battery or alike.

## 5A Variable Power Supply with LM338 Voltage Regulator

5A Variable Power Supply with LM338 Voltage Regulator

The 5A Variable Power Supply uses the LM338 voltage regulator. The LM338 regulator works the same as the LM317 adjustable voltage regulator, known to all

## Inverter for Fluorescent Lamps (12V to 120 / 220 VAC )

Inverter for fluorescent lamps (12V to 120 / 220 VAC)

Simple circuit using the 555 timer, a transformer and a transistor Useful to use with a car battery.

## 12V Power Supply using Zener and 741 Op. Amp.

12V Power Supply using Zener and 741 Op. Amp.

This 12V Power Supply has, as its main characteristic, a low output impedance. This is a very desirable feature in voltage sources and is achieved with a large open loop gain that the operational amplifier has.

## Surge Protection Circuit (Voltage Delay Circuit)

Surge Protection Circuit (Voltage Delay Circuit)

This Surge protection circuit is placed between the DC voltage source and the circuit that you want to power. This circuit delays the voltage given by the power source and allows the voltage to be applied to the circuit or device a few moments later.

## Current Limiter circuit for Power Supply using transistor & resistor

Current Limiter circuit for a Power Supply using a transistor and a resistor.

If the load current exceeds its maximum, an over current protection is needed

## Mini variable Power supply circuit (0-30V, 1A)

Mini variable power supply.

Totally transistorized with 0 to 30V output voltage range, and it can be used for projects where the current consumption is 1A max.

## Variable voltage regulator using 7805 and 741

Variable voltage regulator using 7805 and 741.

Very simple variable voltage regulator with very few components. Output Voltage from 5 to 30 volts

## 12 volt Power Supply using 7805 regulator

12 volt Power Supply using 7805

This 12 volt power supply circuit is simple and very useful. Sometimes a 12 Volt power source is needed, and we only have 5 or 9 volt regulators (7805, 7809)