March 14th, 2009

ATX supply to bench power

ATX power to bench power

This is a very simple to build and very powerful power supply for basic electronics, but for a newbie can seem confusing if he tries to make the conversion on its own. The power supplies used in PC’s have useful output voltages like 5V, 12V, 3.3V and even some negative outputs -5,-12V. While the positive outputs can handle significant current, the negative rails tolerate just a few hundred milliamps.

I recently needed about 12 and 10A, since my bench supply can handle only 2A  I used an old 250W PC source, on the label was 12V/15A but the voltage dropped to 10V at 5A load, so don’t be surprised if you encounter similar “effects”.

Don’t forget the dummy load on the 5V rail, to be honest I never used it and the supply worked just fine, but to avoid any problems load the output with 0.5A. In lack of power resistor use any 12V light bulb, it will do just fine.

ATX power to bench power: [link]

July 16th, 2008

Universal Charger

Universal Charger

The main PCB for the charger is a single sided, 1.6mm tick printed circuit board. The DC/DC converter is now integrated within the charger in order to allow the charge of high number cell packs. The people that charges only few batteries (12Vdc supplies sufficient) can not mount the components for the DC/DC converter saving the money of this part. The DC/DC converter part is a generic step-up converter, capable to deliver 7.5A and an output voltage of 24Vdc, starting from a 12Vdc supply. The main parts are the following:

  • PWM controller UC3843 very cheap and easy to find
  • Power inductor from Bourns, type 2306RC (27uH, 15A), Farnell 1167731
  • The power diode is a schottky type,and a N-type mosfet can be generic: all the two components are in case TO-220

Universal Charger: [Link]

Constant Current Supply For LED\'s

This circuit provides a constant amount of power to the LEDs and also provides a constant amount of light for a longer period of time. This circuit also allows the LEDs to run on almost any normal voltage above 4 volts. This means you can use multiple sources of power for the same light, a few AAA batteries, or even a car battery.

Constant Current Supply For LED’s: [Link]

Mobile infrared electronic transmitter

Negative Power Supply (-5V / -12V / -15V)

Sometimes you need a simple negative power supply. The best example is the contrast PSU for common small LCD device. Building -5V from a battery or a wallmart supply isn’t really easy. The author used the MAX 764/765/766 series to build the power supply. You can simply change the chip to provide the desired output.

Negative Power Supply (-5V / -12V / -15V): [Link]

May 30th, 2008

+/- 15V Power Supply

+/- 15V Power Supply

This is a precision ±15V regulator designed on a single side PCB. The original project is based on EB-802 and belongs to zerosoft. The author took the original project and modified it by replacing some of the components with others that are easy-er to find on the market.

The board has a really nice symmetry design and fits nicely into a case. You could use the regulator to power a pre-amp or a headphone amplifier with great results.

+/- 15V Power Supply: [Link]

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