12bit Power Supply

[ronsimpson]

Very clever. What LCD did you use?
I have on my bench a Agilent N6705A that has many of he same functions. It only costs the price of a small car.

[ztoti]

Hi there,
Thanks for your comment. Anyway I used 128X64 Samsung KS0108 Graphic LCD and matrix keypad which I converted to PS2, or any PS2 numeric keypad.
Cheers

[Ioannis]

Interesting project.

Are you using PID to control the output voltage?

Ioannis

[rmteo]

I'm guessing from the thread title that OP is using an external DAC - so PID is not needed. The MCU's I use have a built-in (dual-channel) 12-bit DAC and I have done something similar. The DAC output is scaled to 2V full scale. An op-amp (rail-to-rail) buffer with 6x gain and a simple linear output stage gives 0-12V output with 3mV resolution.

[Ioannis]

If it is open loop, how is the output voltage regulated with the load?

Feedback is required, isn't it?

Ioannis

[rmteo]

That is the purpose of the op-amp/buffer as in the figure below - the DAC provides the Vin. The gain is changed by altering the values of the feedback resistor pair R1, R2. Gain = (R1+R2)/R2.

[Ioannis]

OK, it is the Vref voltage of the loop that is controlled. So the PIC is not in the output voltage loop.

OK, it has some cons, but with a high resolution DAC it will work just fine.

In fact I ordered a couple of MAX5541, 16bit DACs to play with the idea and build a digital controled Power Supply. One for the voltage and the other for he current.

My dream I had from childhood...

Ioannis