tyrebyter
Member
I want to be able to pick the turn-on temperature and turn-off temperature of an electric radiator cooling fan motor. I also want to use the stock temperature gauge sending unit while rataining normal functioning of the gauge. A bonus would be soft start for the motor and variable speed according to temperature - up to and including full speed as if switched on by a relay. I have a two speed fan motor with two windings that share a common ground. I have a regulated 10 volt supply to the (current controlled bi-metal heated) gauge and have determined gauge resistance and sending-unit-per-temperature resistances.
My head is swimming in PWM circuits, discreet verses, microcontroller verses, 555 timer ic and more. I'd rather be able to fix this if needed so prefer discreet components, tranistors, digital flip-flop gates etc. I would rather not use a microcontroller and software based parameter control functions - if that is the correct nomencalture.
The gauge and sending unit circuit is in effect, a voltage divider. I can figure out how to read the voltage between the gauge and the sending unit using a buffer Mosfet or op-amp. I can figure out how to determine the turn-on and turn-off temperatures/voltages. I am stuck trying to gain enough knowledge to put together the rest of the control functions, i.e. Soft-start, variable speed and in effect a 100% duty cycle if I choose to go the PWM route. If I use a PWM-to-linear voltage controlled function, I am stuck trying to figure out pretty much the same stuff.
Any 1st hand experience/help or links to circuits that could be a part of this controller design would be greatly appreciated.
My head is swimming in PWM circuits, discreet verses, microcontroller verses, 555 timer ic and more. I'd rather be able to fix this if needed so prefer discreet components, tranistors, digital flip-flop gates etc. I would rather not use a microcontroller and software based parameter control functions - if that is the correct nomencalture.
The gauge and sending unit circuit is in effect, a voltage divider. I can figure out how to read the voltage between the gauge and the sending unit using a buffer Mosfet or op-amp. I can figure out how to determine the turn-on and turn-off temperatures/voltages. I am stuck trying to gain enough knowledge to put together the rest of the control functions, i.e. Soft-start, variable speed and in effect a 100% duty cycle if I choose to go the PWM route. If I use a PWM-to-linear voltage controlled function, I am stuck trying to figure out pretty much the same stuff.
Any 1st hand experience/help or links to circuits that could be a part of this controller design would be greatly appreciated.