OpenSprinkler › Forums › Hardware Questions › OpenSprinkler › Does Open Sprinkler AC have power supply minimum/maximum amperage? › Reply To: Does Open Sprinkler AC have power supply minimum/maximum amperage?
@davethomaspilot: the trace width is just a basic guideline and in practice it also has to do with the length of the trace. For example, a short trace with narrow width is not as bad as a long trace with narrow width. In the end it’s the resistance on the trace that matters. Obviously the longer the trace, the wider you want it to be to reduce the total resistance on the trace.
Before I proceed to answer your second post above, let me make sure if your LED runs on 12V AC voltage instead of DC — most LED lights I’ve seen run on 12V DC voltage, so you probably want to check to make sure of that. The reason I am asking is that OSPi cannot switch DC power — due to the way triacs work, it can only turn on DC current but will not be able to turn it off. Actually you can run LEDs on AC power anyways, but you may notice considerably flickering compared to running it on DC.
Anyways, back to your questions: although the ground trace is not wide, there is a whole ground plane, which means each ground trace will only run a short distance before it goes into part of the ground plane. So the ground can actually run a fairly large amount of current.
Another option, if you don’t want to modify the OSPi circuit, is to use relays to switch your LED lights. Specifically, you can connect a 24VAC relay to a station, and that way turning on/off the station actually turns on/off the relay, and you can use the relay to switch whatever device you need. We have published a blog post that describes several 24VAC relay options: