Hello everyone... I know that I am new here, as of about 3 hours ago but I was wondering if anyone could help me out with a circuit I am trying to build.
First a little background info on me. I consider myself to be relatively good with my hands. I took a number of electronic courses right out of high school, but seem to have forgotten a lot of what I learned over the years
I need a circuit to be able to sense a temperature of 420 F and when the temperature reacheds that it needs to energize a relay (normally closed) which will be attached to a light and a buzzer.. so if the temperature is below 420 F the light and buzzer will go on.
I got the idea that I could use a thermistor and have bought several of them with different ratings "all NTC".. some of the circuits I have been able to find range from the really simple sounding
**broken link removed**
to far more complex "for me anyway" circuits
**broken link removed**
I tried the first circuit above with a 12v relay and can get it to sort of work with a 100 ohm thermistor and a pot.... sorry don't remember what rating the pot is, it was just one that was laying around...
The thing is it does not work consistently. Plus I have no idea how to figure out which thermistor/pot combo to use to get it to energize a relay when it reaches 420 F?
I have searched on this site through many a great threads but none really seem to address what I need to have happen in my circuit. Am I on the right track? Can this be done?
It frustrates me because I am sure 11 years ago I would have been able to figure this thing out....
wish I hadn't sold all the books back then! LOL