Adjustable Power Supply Project

[Anonamous]

Hey guys, I was sitting in class doing a lab the other day trying to adjust this stupid power supply needed for the lab and of course, like always, it was impossible to get it to the right setting because pot's are way to touchy. Then I thought about it, what if a digital potentiometer were to be used instead to control the voltage. Of course an AVR or micro-controller would be required but it would eliminate any adjustment issues because we would be able to adjust it by pushing a button instead of turning a pot. Since I have a very limited knowledge of programming, this would be something which I would defiantly require some of your help with.

The design would be simple. First a transformer would be used. Since this is going to be for an adjustable power supply, a higher value transformer (in both voltage and current) would be better to use. It would then be passed through a full bridge rectifier (or four rectifier diodes) then onto a filter or a series of capacitors. This would then connect to a 5v voltage regulator (to power the AVR or micro-controller) and also to an adjustable voltage regulator. We would then use the digital pot (controlled by the avr/micro-controller) to control the resistance values required for the adjustable voltage regulator.

What are your thoughts on this guys, I would really appreciate your help with this and it would be great to be able to start off a project like this from scratch and complete it. This type of thin could benefit a lot of people here at acidmods while building prototypes for their mods.

[hyper999]

No micro needed, you get digital pots that interface directly to push buttons.

Another solution is replace the pot with a 10 turn one, this will give you much more control.

And finally check out EEVBlog [Dave] who makes the blog is in the process of designing and open source, open hardware linear power supply with digital control using an AVR programmed with the Arduino bootloader.

If you still want to use a I2C/SPI/Serial etc digital pot or DAC i highly recommend using an Arduino compatible AVR the programming language is basically C but there is a HUGE amount information and tutorials online.

Keep us posted on how this goes as I am also interested in building myself a decent bench PSU

[FOOKz™]

Another solution is replace the pot with a 10 turn one, this will give you much more control.

...

That.
Stupid-simple and cheapest way to do it.

Instead of one 10K pot, for example, you use five 2K pots in series... you have 5 time more control.

[Anonamous]

That.
Stupid-simple and cheapest way to do it.

Instead of one 10K pot, for example, you use five 2K pots in series... you have 5 time more control.

Ok. Now I know how to go about the actual power supply (Voltage really) part of it. But I am unsure about how to go about displaying the voltage being output.

[hyper999]

- Cheapo Voltage panel meter

- Micro controller and some sort of LCD or LED display

- etc etc

[Kool1zero]

buy a cheapo multimeter, cannibalize it for the meter part, just leave it to across the whole pot( or pot array) and call the metering part done. other than that you would need to use and A/D converter and take the digital out, convert it to binary, and use the binary with a driver chip to run a couple 7 segment displays or the like. or a microcontroller with an integrated A/D and the 7 segments and a driver chip.

[Anonamous]

this is the schematic I have so far. The resistor values for the LM317T adjustments are not final yet. I am also unsure whether or not I should put in a 40V voltage regulator in before the LM317T so that there is a steady voltage going into it to help keep the output accuracy.