not sure what I need

[jeff20032]

I have an old lab type 110 volt drying oven. currently it has two thermostats mounted to a dial. I the thermostats are dead but the heater and fan motor will run. I would like to convert this over to a digital style controller. What do I need to run this monster.

[richiem]

Depends on the temperatures you expect to run at. Probably a JLD612 and the K thermocouple that comes with it will be fine. You need to know how much current the heater uses, which you may be able tgo find on the unit. If not, it means hooking up an AC ammeter to the heater -- if you have a clamp-type ammeter, then just clamp it around *one* of the heater wires and connect the heater to the line voltage and measure the current. If you have an ammeter with leads, then it needs to go in series with one of the heater leads. Then hook it all up to the line and measure the current.

Once you know the amount of current flowing to the heater, you can choose a solid-state relay (SSR) to control the power to the heater, and drive the SSR from the JLD612. Be careful to match the polarity of the 612's SSR output to the polarity of the SSR's DC control input.

In general, I recommend using an SSR rated for about 5X the current that the heater actually needs. The k thermocouple needs to be located where it can sample the temperature of the air that's being heated. You need to specifically reset the 612 to work with the K thermocouple -- read the manual. Use a heatsink on the SSR!

That's all of the hard stuff. Come back with further questions.

[jeff20032]

Thanks.