I am trying to build a device that is based on adjusting the speed of dc fans. First I tried using a prewritten PIC program, but this failed, and I do not know enough C coding to program an AVR chip, which I could get some help with.
Now I want to make a purely analog device. I am thinking of using an LM317 variable voltage regulator, and a potmeter. (and of course various diodes, resistors and capacitors) I have a transformer that provides 18VAC. My fans can operate from 4-12VDC, possibly slightly higher. What I need is a way to make a cutoff switch off power at 4V, to protect the motors. I am thinking of using a zener diode and a transistor to block anything below 4V. Does anyone know if this will work? how should I wire it? what rating should I use for the components?
My basic design works without the low voltage switch.
Now I want to make a purely analog device. I am thinking of using an LM317 variable voltage regulator, and a potmeter. (and of course various diodes, resistors and capacitors) I have a transformer that provides 18VAC. My fans can operate from 4-12VDC, possibly slightly higher. What I need is a way to make a cutoff switch off power at 4V, to protect the motors. I am thinking of using a zener diode and a transistor to block anything below 4V. Does anyone know if this will work? how should I wire it? what rating should I use for the components?
My basic design works without the low voltage switch.
