I ordered a new LED anchor light that is supposed to turn on automatically at night. Imagine my disappointment when I installed the light (after an eleven-hour round-trip to Tucson to pick it up) to learn that it emitted RED light! The company I ordered it from apologized and sent a replacement. After another trip to Tucson to pick it up, imagine my continued disappointment to learn that the new light has a different mount AND it does not have the automatic on/off feature. A call to the company confirmed that the lamp they sent me is all that they have. Since I am restepping the mast in a couple of days, I did not have time to arrange for a new light, but I really wanted the automatic on/off feature. So … I ordered a small circuit board from Amazon (with one-day service) that is designed to turn automobile headlights on automatically at night. Naturally, the circuit board came with ZERO instructions. Here I am doing a quick test of the circuit using my car battery to confirm that it works.
The white wire in the lower left had the photodiode at the end (covered with black electrical tape). A few tests demonstrated the relay on the board can either be configured normally on or off. The first time I wired it backwards (the anchor light was on during the day), but switching a couple of wires fixed the problem. Since I imagine this add-on would be of interest to other sailors, I will post the details later.