I decided to give my digital power supply a nice permanent casing using the Industruino PROTO system. This is an Arduino compatible DIN-rail mountable box with an LCD screen, prototyping area, and lots of convenient connectors.
As described in my previous posts, the system is based on a DC/DC converter, hacked with a digital potentiometer, and a shunt resistor to measure the current. I solved the problem of low resolution of the current measurement described here by using a specialised opamp, TI INA210 with a gain of 200. I chose a 0.1 Ohm shunt resistor, which gave me a range of 0-250mA based on 5V Aref (5V/200 = max 25mV over the shunt resistor => 250mA).
The Industruino is a great platform for building this kind of projects: it enabled me to include all the components in the prototyping area and use the connectors to bring in the 12V from the wall wart, and 2 wires for the output.
The result is:
- DC/DC converter driven by a digital potentiometer and PID control
- Set target voltage with the buttons on the Industruino panel: up/down and enter to confirm target voltage
- Shunt resistor with opamp to measure the current (0-250mA range)
- LCD shows target voltage, output voltage, output current
- DIN-rail mountable robust housing for Arduino project
More details on the Industruino blog.