hi guys, i need some help finding a pot with the right resistance range. im working with an automotive circuit, so somewhere around 12v, and im trying to vary the speed of a cooling fan. im using a toggle switch and a relay that switches output from one lead to another when the coil is energized. so basically, with the switch off current runs through the normally closed lead of the relay, through a resistor, to the fan, and to ground. with the switch on, current runs straight from the relay to the fan.
ok, so the max current draw of the fan is around 6.8A, so resistance is 1.77 ohms...if i want the fan to run at 1/4 speed, i would need to increase resistance to 7.1 ohms, if i want it at 3/4 speed id need 2.4 ohms, etc...
id like to use a potentiometer in place of the fixed resistor, so that with the switch off i can run the fan, ideally, from 1/8 speed (14.1 ohms) to 7/8 speed (2.0 ohms), with the switch on, full speed..actually, if i can find the right pot, i may use one on each path so that i can set both switch positions to whatever speed i want..
now, maybe i just dont know how to read the specs, but all the pots ive found are rated at like 10k ohms.....the fan will barely run with that much resistance...anybody know where i can find a pot with the resistance i need?
thanks guys
ok, so the max current draw of the fan is around 6.8A, so resistance is 1.77 ohms...if i want the fan to run at 1/4 speed, i would need to increase resistance to 7.1 ohms, if i want it at 3/4 speed id need 2.4 ohms, etc...
id like to use a potentiometer in place of the fixed resistor, so that with the switch off i can run the fan, ideally, from 1/8 speed (14.1 ohms) to 7/8 speed (2.0 ohms), with the switch on, full speed..actually, if i can find the right pot, i may use one on each path so that i can set both switch positions to whatever speed i want..
now, maybe i just dont know how to read the specs, but all the pots ive found are rated at like 10k ohms.....the fan will barely run with that much resistance...anybody know where i can find a pot with the resistance i need?
thanks guys