The two LED's are output indicators. I have attached the manual for the controller, it's an 04 type.
So if I go with Arduino, It will be larger than the housing I have (itron 04). What I was initially hoping was to be able to force a value on the LED's by way of set voltage (emulating a probe voltage at 78 and 26). The problem with the controller is the on board buttons do not work, but I can change settings with a jumper wire across the button circuits on the board. So, theoretically, what if I just told it to keep 78degF and then send that corresponding voltage to the input terminal? How would I figure out what voltage that would be, then how to a make it? The only problem with doing that would be no symbols (F or C). I could have a button wired to the input terminal with the two voltages for switching.
if I use a Nickel-Chromium Type K, can I just take the low voltage from the board and resist it town to 1.249Mv (78) and send it right to the input? Is this even feasible?
If your controller is working enough to do that, then that would be the easiest way. I was assuming that the controller just flat-out didn't work. It is normally connected to a thermocouple to sense the temprature. A thermocouple generates a voltage, so you only need to simulate that voltage, as you say. The easiest way to find out what that voltage is is to look up a datasheet for the thermocouple. It will have a formula in there that you use to determine the temperature based on the voltage. Just reverse the math. Or, you could just go and measure the voltage on one that is in use at the temperature you want.
It sounds like the switches are probably just broken. Why not just replace them with your own?
A voltage divider would work, yes. Two resistors. You tap off the center and input that into your thermocouple input. BTW, your datasheet for the iTron was corrupted so I can't open it. Does it have the pinout?
I'll try and post it again. I'm probably the first person here to ever take one of these controllers apart. In the past when they stopped working (meaning un able to adjust parameters) we just replaced them. Now that I see the buttons are just worn out, I could fix with aftermarket buttons, but would be hard to make it fit back together in its nice enclosure. I really wish I could make it read F or C after the temp. Maybe deep in the manual I can find that. Otherwise, may have to go with the arduino and build an enclosure. But I'm not giving up on modifying the itron!
edit: it shows corrupt when i click the link, yet it opens fine on my computer????? Here's a link to the manufacturer site, under documentation is the datasheet and manual.