I’ve mentioned before that I’m building an Evapotron, a device for making grey water (i.e., water used for washing dishes and people) evaporate so it doesn’t have to be packed out.

Today I tested a mechanism for driving grey water up and over the pumped cascade which is the model for this implementation. In short, I need to get dirty water out of a reservoir, lift it about 6′, and let it dribble over a snow saucer and thence down a cylinder to be exposed to sun and wind. A friend suggested that a submersible bilge pump would be a good choice.

I got a couple of Rule 25s automatic pumps. These guys have an internal circuit to check every 150 seconds if there’s water present. If so, they run ’til they suck dry, then go back to waiting. That’s perfect for this application. I’ll power them with a cheap 12v lead-acid battery. In the first test, it works.

The battery will live in a sealed (against dust and water) clear plastic box next to the bucket where the pump sits. Inside the box will be the battery and a charger. The charger will connect to the (highly flaky) camp AC. The charger is “smart” in the sense that it knows only to charge when the battery’s voltage is low. Still, I’d like it to turn off periodically, and I’d like to turn the pump off at about 7pm through about 8am in the morning. I’m thinking of building a real time clock + Arduino that could control the charger via a PowerSwitch tail and the pump via a relay.

I can think of many other uses for such a circuit. For example, it would be nice to turn on a power strip that charges all my rechargables one night per month (they usually sit dormant for months and die). It might also send me email about the status of the batteries.

Anyway, my project partner P has a bunch of good ideas for the actual mechanism of the Evapotron. I think this is going to be excellent.