Need temperature controlled DC motor speed

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Joined May 13, 2009
I have a 12 VDC fan motor that draws over 40 amps. I need to control its speed from zero to full speed based on the resistance of a temperature sensor. Any ideas?



Joined Aug 7, 2008
A few thinking points:
A Use neg. lead from power supply to motor as currens sense.
B Use one or two Si diodes as temperature sensors.[ give reasonable linear output ].
C Operational Amplifier to adjust offset, inversion & supply gain.
D Use Sgt. Wookie's voltage controlled PWM ckt.
E FET driver.
F Several low RDS, high current FETs in parallel.
G 40As of back EMF supression for motor.


Joined Jul 17, 2007
Hello again Jack,
You've been away for awhile. Nice to see that you're still alive 'n' kicking. :)

Unfortunately for your topic, the Terms of Service has been amended during the time you have been away. If I may call your attention to the following paragraph:

6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in your thread being closed without question:
  • Any kind of over-unity devices and systems
  • Automotive modifications
  • Devices designed to electrocute or shock another person
  • LEDs to mains
  • Phone jammers
  • Rail guns and high-energy projectile devices
  • Transformer-less power supplies
In light of (to you) the new policy on this type of topic, I'm afraid that this Forum will no longer support these discussions, so this thread cannot continue.

There were a number of reasons for the new policy, but mostly it was due to the number of neophytes engaged in functions that really required automotive engineering expertise; the failure of their intended projects could have resulted in dire consequences. While I know that you don't exactly fall into that category, the rule is global for these Forums, and exceptions to the policy are not made.

However, this topic:
contains links to various other websites where such discussions might be entertained.
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