Until then I used and ATX power supply with an ATX breakout board. I provides all voltages needed for electronics: 3.3 V, 5 V, and 12 V. But you can't set the current. It only comes with a 1.25 A polyfuse.

So I decided it was time to buy my first bench power supply. But is had to fulfil the following criteria:

• set voltage and current
• wide voltage range (0-50 V)
• silent
• have an earth connection
• not expensive
• not noname
• provide a communication interface (most important)

I found and bought a used power supply on eBay for ~ 80 €. And now I own an Elektro-Automatik EA-PS 2084-03 B power supply. And this fulfilled are the requirements:

• set voltage and current: in 0.1 V and 0.01 A steps
• wide voltage range (0-50 V): 0-84 V, 0-3 A (not a lot, but enough for electronics), limited to 100 W
• silent: not fan, full passive cooling
• have an earth connection: on the front panel
• not expensive: ~ 80 €
• not noname: Elektro-Automatik (never heard of it, but it's German and they have a decent website)
• provide a communication interface: USB with proprietary documented protocol

Here some more documents about this power supply:

• datasheet (archive)
• manual (archive)
• programming manual (archive)
• driver (USB ACM for Windows)
• easyPS2000 software (Windows, demo only)

When powering the device on, I noticed that the voltage on the display did not change while I was turning on the knob. But the Digital Multi-Meter (DMM) actually shows that the voltage actually does change. Just the reading on the screen is inaccurate.

It was time to measure how inaccurate this power supply is. But doing that manually just takes to long. So I decided to implement the protocol to control the the power supply, and I will measure the set output using a DMM connected to the computer.

To control the power supply I implemented the protocol described in the programming manual. The source code is available on git.

The control programming will increment the voltage from 0 to 84 V in 0.1 V steps, at 1.0 A. It will set the voltage and current which are set, actual (measured by the power supply), and measured (measured by the DMM)