There is a gas fireplace in the basement. It keeps the room as warm as you like. The fireplace is at one end of the big room and there is a thermostat at the other end of the room. I could never get the original thermostat to behave like I wanted, too large a temperature swing maybe. It's been a long time, so I don't rightly remember what the problem was. In any case I bought a new thermostat and it was satisfactory until it quit. Seems the old thermostat used a mercury switch and the new thermostat had mechanical contacts. The new thermostat is supposed to be used with a 12 volt control circuit, but the gas valve in the fireplace runs off the millivolt current supplied by the thermopile. It's like 600 millivolts which is less than one volt.
I don't know whether it was dust or corrosion on the contacts in the thermostat, but I cleaned them up and they worked for awhile, but then it quit again. Obviously I need a better solution. So then I got the idea of using wall-wart to supply voltage to a relay to trigger the gas valve.
12 volt relay designed for use in a car ought to do the trick, but none of the old wall-warts I had lying around produced 12 volts. I even tried using a USB plug, but it didn't have enough oomph either.
Finally resorted to buying this LED power supply. 3 amps is overkill for what I'm doing, but it works a charm.
After the thermostat quit, I resorted to using the switch attached to the gas valve. Awkward being as it is behind the lower grill and down around ground level, but it worked. Until it didn't. Time for a new switch.
Don't want to wear out the new switch, so I resorted to connecting the two wires together with a splice connector. Once again that worked for a while until the it didn't. Connector is only supposed to connected and then left alone. It is not designed to be used as a switch. That's okay, I've got a bunch of these connectors, I can just throw out the old one and put in a new one.
Of course, using a connector to turn the fireplace on and off is silly, especially since I have all the parts I need to implement my relay scheme. Today the boss is on a tear and something must be done about all the valuable stuff I have collected in my dungeon. Fine, okay, I'll hook up the relay. After stalling for ten months it only took me 15 minutes to hook it up and so far it's working.
| Date | Item | Amount |
| Oct 15, 2021 | Thermostat | 33.81 |
| Mar 13, 2025 | Relay | 7.95 |
| Mar 13, 2025 | Connectors | 8.99 |
| Dec 22, 2025 | Switch | 15.99 |
| Dec 25, 2025 | Power Supply | 9.96 |
| Total | $76.70 |
I sacrificed an old extension cord to feed 120VAC to the power supply.
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