Firstly, I did do a search (http://forum.allaboutcircuits.com/showthread.php?t=69524&highlight=thermal+fan+controller) and my question was not addressed in the results.
I am building a cooling unit for my entertainment center and have run into a problem (potentially).
http://www.sentex.ca/~mec1995/circ/auto-fan.html is the source of my circuit and I have followed it as closely as possible (the one amp relays I got from Radio Shack do not fit the breadboard properly). I am using 5A relays instead. My plan is to have two sets of two fans controlled by separate thermistors (and a single pot if possible) to cool two zones. I will make a probe out of each thermistor to ensure that each zone is only cooled when necessary.
I have the circuit working to turn on a single fan wired directly to the breadboard, but it never turns off. I don't know if there is a problem or if the threshold to turn on is simply too low. My house is still over 84° F at 11 p.m. so it may be that, but is there a way I can know for sure without simply waiting for cooler weather?
I am a computer science student, not an engineer and this is my first attempt at making an electronic device, so I really don't know this stuff. I would imagine there is a formula I can apply as long as I can get the information about my pot and thermistor.
If needed, I was thinking of adding the requirement that our googletv blu-ray player be powered on. Is adding a third relay which would affect the presence of voltage to the rest of the circuit the best way to accomplish this?
By the way, I am going analog for now, but eventually I will probably build this into a digital device.
Also, I have a couple of questions about best practices.
1. I set up an excel file to plan my breadboard; is this okay?
2. Should I find a way to test the 1A relays before using them? There is continuity between COM and NC and with power applied across the coil it does audibly switch, but I have not devised a way so far to check the NO pin with power applied (haven't spent much time worrying about that).
I am building a cooling unit for my entertainment center and have run into a problem (potentially).
http://www.sentex.ca/~mec1995/circ/auto-fan.html is the source of my circuit and I have followed it as closely as possible (the one amp relays I got from Radio Shack do not fit the breadboard properly). I am using 5A relays instead. My plan is to have two sets of two fans controlled by separate thermistors (and a single pot if possible) to cool two zones. I will make a probe out of each thermistor to ensure that each zone is only cooled when necessary.
I have the circuit working to turn on a single fan wired directly to the breadboard, but it never turns off. I don't know if there is a problem or if the threshold to turn on is simply too low. My house is still over 84° F at 11 p.m. so it may be that, but is there a way I can know for sure without simply waiting for cooler weather?
I am a computer science student, not an engineer and this is my first attempt at making an electronic device, so I really don't know this stuff. I would imagine there is a formula I can apply as long as I can get the information about my pot and thermistor.
If needed, I was thinking of adding the requirement that our googletv blu-ray player be powered on. Is adding a third relay which would affect the presence of voltage to the rest of the circuit the best way to accomplish this?
By the way, I am going analog for now, but eventually I will probably build this into a digital device.
Also, I have a couple of questions about best practices.
1. I set up an excel file to plan my breadboard; is this okay?
2. Should I find a way to test the 1A relays before using them? There is continuity between COM and NC and with power applied across the coil it does audibly switch, but I have not devised a way so far to check the NO pin with power applied (haven't spent much time worrying about that).