I've been playing with electronics for a long time, but am fairly new to digital electronics, including using Fritzing, so apologizes in advance for that.
I'm attempting a fairly basic
5VDC circuit where I want to use a thermistor to toggle a fan on and off, and to be able to set the point at which the fan toggles.
I know I could use Arduino to read the resistance from the thermistor and the potentiometer and, based on logic, supply high or low to the relay switch - but how would I build the circuit without an Arduino? Would I still need to use an IC for the logic?
I was thinking I could potentially use something like an AND/OR gate with the feedback from the thermistor circuit to control the relay ( thus giving the relay either high/low and not a variable voltage ) but the of course the AND/OR gate is going to get the variable voltage which seems wrong to me ( analog feedback to a digital component ) and so I know I'm missing something - a small I/C that can read the analog voltage would seem to be the "right" thing but it also seems like there may be an easier way to do it with such a simple circuit.
Below are the Schematic and Breadboard views from Fritzing. I know they are incomplete, and that the power supply is 6v instead of 5v, but hopefully it will help convey the basic idea.
screen 1.png http://img843.imageshack.us/img843/5582/q7yq.png