They're probably Ada's, to be honest.
I've just ordered three circuit boards for the initial prototype for testing/sizing, for what it's worth. $12.14 for three with tax and shipping. I'd call that a deal.
Shouldn't the diode in the circuit diagram pointing in the other direction?
No, it's correct the way it is. When the relay is switched off, the coil inside creates a current that is opposite the former current, so the voltage is also is reverse. To protect the semiconductors (here the transistor), this voltage is shortened by the diode.
Saved by the diode. (yay)
The first group of three prototype boards came in and I just soldered one up since I had the parts from earlier. I'll need some thinner tie wraps to go through those holes for cable management and I suppose I'll now need to design a plastic case. Other than that, it seems to work as expected.
Back from vacation and I've now designed/printed an enclosure. I've used a simple tight rubber band which came on a William Sonoma whisk to hold the two halves together.
$15.00 approximate total cost of parts if you make more than one of them.
I created a wikifactory page for this project. (Enjoy)