12V DC Speed Controller
12V DC Speed Controller
(OP)
Can anybody help with a simple schematic for a (simple) speed controller for an automotive fan. It consumes about 15A at full voltage (12V DC).
A PWM design with low losses would be preferred.
A PWM design with low losses would be preferred.





RE: 12V DC Speed Controller
Check TI's TL494 spec sheet for some simple control circuits built around a pretty standard controller. You'll need a drive element capable of your 15 amps (darlington)and a PWM controller (TL494). This device has onboard drivers capable of driving your switching element, as well as error amps for feedback control. You'll simply feedback the motor voltage to an onboard error amp. The difference between this feedback and your reference input (speed signal) results in motor drive.
Back to the original problem, how do you derive a speed signal?. Maybe a stacked comparator that switches a relay(s)the select a resistor combination is adequate. This could easily give you several speeds as opposed to full on/off.
RE: 12V DC Speed Controller
Look at these:
http://www.4qdtec.com/pwm-01.html
http://www.solorb.com/elect/solarcirc/pwm1/
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http://www.discovercircuits.com/M/motor-cont.htm
RE: 12V DC Speed Controller
I do not presume to speak for all of the Eng-Tips community, but I find it exceedingly irrating when someone posts a question and expects us to know the best solution. Every solution has its pros and cons. When posting a question, pretend that you are asking your boss for help. Prove that you've done at least the most basic of groundwork, and that you don't want someone to actually do your work for you. I am sure that everyone here would like to point you in the right direction, but don't want to solve the problem for you!
RE: 12V DC Speed Controller
Check out power supply circuits, there should be some that meet your requirements.
Of if efficiency is not important, place a power transistor with a heat sink in series with the motor and vary the drive current (Or voltage if using a FET).
DISCLAIMER: The preceding will not give accurate speed control and may not work with some motors.
RE: 12V DC Speed Controller
RE: 12V DC Speed Controller
RE: 12V DC Speed Controller
I used a similar way to speed control a fork lift runs on 2 dc 2 motors 200Amps 48 volt each
RE: 12V DC Speed Controller
FET's are nice, but they can also create other problems. Try a IGBT (Insulated Gate Bipolar Transistor). These devices have the drive strength and voltage drop of a BJT, but the input drive levels of a FET.
RE: 12V DC Speed Controller
RE: 12V DC Speed Controller
RE: 12V DC Speed Controller
RE: 12V DC Speed Controller
http://www.onsemi.com/pub/Collateral/2N3055-D.PDF
Others are not that much better:
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Compared to Hexfets:
http://ec
TTFN
RE: 12V DC Speed Controller