I am building a setup using Arduino to control the light output of a 120v 75w bulb on my reptile cage. I want to place a temperature sensor inside the tank on the basking spot and the cool side. I want Arduino to regulate how much light comes out of the heat lamp based on the temperature so that it is at a steady 110F. I have two issues that I am trying to figure out..
Temp sensor: I bought a tmp36 temp sensor and placed it on a 2 foot cable and tried reading the temps. They were all over the place and not steady. So I cut the cable and tried using 2 inches, and the temp is pretty steady (goes up or down 1 degree sometimes). I need to have a temp sensor that can be on a 6 foot cable from the Arduino to the inside of the tank. Which temp sensor would achieve this and be very accurate at doing so? If I need to buy some new ones I don't mind, I just want to make sure that the reading are correct and steady since this will control how much light is put out.
Dimming 120v 75w bulb: How would I dim the heat lamp bulb using arduino? I could place a servo on the dimmer that comes with the bulb, but I don't believe this to be the best way.. I think the best way would be to have some sort of circuit board that arduino would interface with and control the dimming. It needs to be able to step up/down in increments since it will be controller by the temperature.
Any feedback is greatly appreciated. I want to make sure I do this correct because I don't want the bulb turned up too high or too low because the temp sensor isn't reading correctly or the dimmer is malfunctioning.