I've been almost totally dedicated of late to other projects but I'm going to try to come back to the Hydra now.

One thing I discovered not too long ago was that the triac was previously wired wrong. It turns out that triacs are not actually unpolarized devices, at least from the point of view of the gate. The gate needs to be taken towards the opposite main terminal to switch it on, and when the triac is on, the voltage across the main terminals will be near zero (because the triac is conducting), which dramatically reduces the current through the other components involved in triggering. Oops.

So the AC board's contactor drivers work a lot better now. I'm going to keep using the half-watt components just to be sure.

One of the fellows who bought a Hydra board set (I won't name him just because I haven't asked his permission first) has contributed to the firmware development in a big way, and a lot of his changes are going to make it back in. This will include some self-tuning for the RTC chip's trimming register (if you set the clock when it's wrong it will get better). He requested an i2c header for the board to add the ability to add off-board sensors, such as temperature sensors and the like. We'll see how much more we can cram into the firmware now that some of the space has been reclaimed by cleaning up and de-duplicating.

What remains is the continuing difficulty with the relay test. To recall, we want to strategically set up a small leak from the relay test pins to ground and measure the current flow. When the relay is open, there should be no current flow, and when the relay is closed, there should be some. But for safety reasons, it's undesirable to leak more than 1 mA of current, but our detection threshold needs to be 24 kΩ. I think the solution is going to wind up involving an isolated power supply. A small 12VDC -> 5 VDC isolated module would work. The idea would be to set up a voltage comparator across a resistor in the leakage path, and then run the output through an optoisolator with the optoisolated output going back to the controller.

I haven't sat down to figure that one out yet. I think the challenge is going to be to make it work without dramatically increasing the size or price. We'll see.