12 volt automotive fan speed controller

[mark krawczuk]

hi, i am after a basic type schematic to controll the speed of a 12 volt
dc automotive cabin fan .

seems to be a bit of a problem in these saab`s.

any schematic using a mj11032 or mj11016 darlington would be good. if
not any electronic speed controll schematic will be fine.
the original darlington is rated at about 25 amp , seems a bit excessive....
these darlingtons i have are rated at 30 and 50 amp.

thanks, mark k

 

[Lostgallifreyan]

hi, i am after a basic type schematic to controll the speed of a 12
volt dc automotive cabin fan .

seems to be a bit of a problem in these saab`s.

any schematic using a mj11032 or mj11016 darlington would be
good. if not any electronic speed controll schematic will be fine.
the original darlington is rated at about 25 amp , seems a bit
excessive.... these darlingtons i have are rated at 30 and 50 amp.

thanks, mark k

556? (Dual 555 timer). Astable triggering a monostable, change monostable
width to get PWM output. Also, a power MOSFET will be more efficient than a
Darlington.
I'm not sure which speed is best for the astable, I'd choose either a few
tens of KHz, or a few tens of Hz, the lower setting is probably the better
one. Either way you want to avoid hearing it.

 

[Marra]

A pot driving a MOSFET would work best and simplest.
The MOSFET would need a heat sink.

 

[Jamie]

A pot driving a MOSFET would work best and simplest.
The MOSFET would need a heat sink.

That may not be such a good idea if you were to use a
fet that was only spec out for logic operations.
You may find the wattage factors on these fets are much
lower than you would think with the currents they can handle.
it's all about the "ON" resistance for the DS... if you
were going that route. You might was well just stick to a
bipolar.

A Fet can be used, simply by using a 555 Timer and vary the
duty cycle driving the gate..