Verdris

You would not need to do it for the logic speed, but consider whether those grounds are carrying power between the boards.

If they are, you may still need a few grounds (rather than just one) to ensure they provide a low resistance path between the boards. The fewer grounds the higher the resistance, the hotter they could get, and there would be a voltage differential between the boards which could confuse the logic gates.

 

Paul

Thanks for the reply. The grounds aren't carrying power, they're strictly logic reference. I've got many other power grounds.

It sounds like a Raspberry Pi would be more suitable.

I'd do two identical water temperature sensors, one in the tank and one somehow in the bowl. If the readings differ significantly for a while after someone has left the bathroom, they probably didn't flush.

Programming this to work with the Netduino will probably take you less time than waiting for someone else's code. I've used SHT21s before and they're incredibly simple. However, don't query them more than once per second as they're prone to self-heating.

Ok, so basically you'll be using a software hp filter then, I suppose there are ready made functions for that in LabView but designing one in h/w is quite simple, basically you put a capacitor in series with a resistor to ground.

Might give this a try. Thanks!

Edit: gave it a try. It worked, but not as well as our current filtering idea which is the LabView-provided minimum for the differential amp.