Power Controller v2 Testing
On Monday the new PCBs for the power controller arrived and this past week has been spent assembling and testing the board. The TL:DR is that testing is nearly complete and so far no major issues have been found. These new boards implement a new bus control architecture along with lots of little tweaks and updates from the v1 board aimed at making it more robust.
Despite the success there were a few setbacks. The biggest issue found was that I was missing diodes on the bus override switches (oops), so if you left the switches in the ON position but were in override mode, it could result in some busses being erroneously turned on in specific scenarios. This is easily fixed by adding the diodes in series with the switch headers which will will connect the switches to the board. The second issue was the lack of pull-down resistors on the bus control outputs. This was a bit of a calculated mistake, as I planned for the LEDs to function as the pull-down, although I neglected to realize that unlike using a normal diode for pulldown which brings it pretty close to 0v, the LEDs forward voltage is way higher, so it only pulls down to ~2.3v, so not a great pull down after all... After some testing I determined only ~10uA was needed to pull it to ground, and when testing with the actual relays connected it was no issue and didn't result in any erroneous activations. So both problems turned out to be no big deal, although certainly if a v3 is ever made they'll be included as fixes.
Despite some setbacks and discoveries I was able to complete probably 95% of testing and at this point am comfortable saying the design was a success and it's ready to go in the plane. Next step will be to update the front panel on the rack and build the wire harness, so when I head to the hangar it'll be a quick installation. There's still a little bit of testing to do, I need to check out the onboard 28v regulator as well as update some of the rack schematics and figure out a plan for adding the aux bus terminals and low voltage DC converters, but none of those will be big tasks.
Giving myself a break from debugging, I've been doing some upgrades to my lab bench. I got some new equipment, including a new function generator which links with my oscilloscope via LAN and opens up the ability to do bode plotting and all sorts of AC/freq. domain testing. Since the next project in the pipeline is the audio interface cards, these upgrades will come in handy over the next month or two and make designing and testing those boards 10x easier. Some networking updates and a fresh OS install on the lab computer have also made my workflow a bit easier. I still have some more upgrades planned including building a new shelf, but the equipment stack-up should be set for now and ready for some audio work to begin.