Mt Wombat Power Distribution

[VK3YNV]

Update from yesterday:

Just back from a trip to Mt Wombat, the power management system has been removed for repair, after another failed relay. When the replacement relay was installed, something else failed and released the smoke. The brand new replacement relay from element14 had a shorted coil which didn't help.

Tracks blown off the pcb that shouldn't have and Josh is busy rebuilding it. Making some upgrades at the same time.

 

[Josh]

I believe I found a probable cause of the issue with the DC power distribution board on Mt Wombat.
First the replacement relay had a diode internally the wrong polarity for the distribution board. The original relay did not have a diode. Pluging in that relay shorted the supply through the diode, blowing the relay coil supply traces off the board.

Second the transistor that drives the Mains Isolation relay had a dry solder joint: the base pin did't look like it had wetted the pad when I remove it. I've replaced all the relay transistors as the relay diode current is likely to have passed through them and if it blew traces of the board they are probably suspect now. They all test fine but I've replaced them anyway. This dry joint could explain the three non commanded changes in state observed(one last year(or the year before), one in jan this year, and one this past weekend. Considering I'd not soldered it properly its odd that it was not more problematic.

I'm taking the time now to upgrade the current sense ic with one that has double in the input range which will give us up to 40 amps measurement without changing the shunts, as I don't have any shunts appropriate in stock atm.

I do have to update the code for the new current sense ic, which will take a bit more time.

I've also given the board a good clean.