Quad 10 A current sink project, part 1: Intro
Channel: FFcossag
Date: 2015-03-24

This project has been in the making for a few months by now, but it's only recently started to manifest in something more than a BOM, a Seeedstudio order and a heatsink with 20 tapped holes drilled into it.

The credit for designing, laying out, programming and ordering the load PCB goes to my very good friend Mathias. I had little to do with the design process of the boards, beyond specifying the design requirements, providing feedback during the design, assembling the boards and stress-testing the circuit.

Schematics and layouts are currently not available, since everything is still incomplete and untested, but it's going to be open source hardware and software later on.

The design requirements for this device were:

1. 4X 1-10 continuous A sunk at 3-15 V
2. Under-voltage protection through 4-wire measurement
3. Electrical isolation between four independent channels
4. A 250 V, 16 A capable relay contact for connecting an external charger
5. Daisy-chainable 2400 baud communication through an electrically isolated I/O for at least 4 units
6. Data logging of the load voltages to a PC (primary), through an electrically isolated serial port, or an internal EEPROM (secondary), at a minimum interval of no more than once per second.
7. Operation without external power supply on voltage sources greater than 10 V
8. Ability to operate on an external 12 V power supply for testing voltage sources lower than 10 V
9. All possible components should be through-hole
10. The device is to be built onto a 5 x 5 cm board
11. One front-panel LED and one button should be connectible to each board
12. The unit should be resilient to abuse through circumstance (ESD, disconnect under load, over temperature)
13. All relevant parameters (sunk current, logging parameters, timing, patterns, etc.) should be adjustable through a PC interface