PWM control of blower motor

i have now built up a working prototype to give variable speed control of the internal blower fan. it needs some fettling... but i am going to create a how to, for anyone interested in doing away with the resistor block hidden in the depths of the car and instead using a potentiometer that fits in place of the switch assembly with its own on/off position..

i only share this thread, because i seek input from those who have done it before themselves , and understand electronic circuits and methods.

i am using an astable 555 timer connected to an IXFH58N20 hypermosfet, at the mo, the res/ cap - pwm control allows me to vary the voltage to the blower between 8 and 11/12V DC, as an average..., i need to alter the rc to make the off time longer and the on time shorter - to get a lower average than 8V and because the blower uses a lot of current when at full speed... maybe 16A, the heatsink i am using to dissipate mosfet heat, gets quite warm.. 118 degrees c at max revs of the blower.. i am going to upload pics and stuff and continue the thread if i get some interest from others who have considered it and might offer help..
i dont have a scope.. i cant see the pwm waveform, and i cant measure high DC current with my DMM this mo. so anyone who has done stuff like this who can advise or help is welcome.

The circuit i am using this mo... is this one with three changes... D1 - 1N5048 C1 680uF and IXFH58N20 mosfet... otherwise the same.
http://ift.tt/2ayQAVr

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Last edited by Incony; Today at 11:23.

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PWM control of blower motor