Hacking into Fan speed switch...
hey, ive got an idea to control my HVAC via carputer and need to discuss some circuitry with you guys.
Firstly, I have 5 fan settings : 0 1 2 3 4
These are controlled by a rotary switch. The fan harness has 5 wires: one for each speed and ground. When in position 1, wire 1 and ground and connected. So on and so forth. Obviously in 0, nothing is connected.
To control the fan speed, i was going to use a Crystalfontz 633, which can control 4 PC fans. I was going to use each fan output as a ground for a relay or something which would connect the appropriate fan speed wire to ground. I would have to be careful though and make sure no two fan outputs were on at the same time, because that would short some **** out.
Someone was mentioning to me that they wished they had more control over the fans, as they liked more air than 1, and less than 2. I thought about it for a little bit, and realized that the Crystalfontz also does PWM to the fans...
so, what if i used fan speed 4, which would make the fans blow maximum, but used PWM. That way, i also wouldnt have to worry about shorting anything out and i also have better control over the fanspeed.
How would i make the circuit though, i would need something to handle all the current of the blowers, and i dont think a relay could handle fast switching of PWM...so is this even possible? I would like to make at least a test circuit, to see how the blowers respond to PWM. I know some fans/blowers make extra noise at certain PWM levels.
thanks for your time