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Brushless DC motor question

Brushless DC motor question

Brushless DC motor question

I have a squirrel cage fan used in a car about 6" (15 cm) diameter. It is a part of the climate control seat blowing air to the seat bottom and back. The control board is built in the fan assembly. 4 wires are soldered to it, M+, M-, Control and Tach. My goal is just to make it run even at one speed. I suppose M+ and M- are for 12V power. What is Control? Thank you.

RE: Brushless DC motor question

I'd guess it's 0 to 12V fed by a dash adjusting knob that's a potentiometer used to control the speed. It could however be a 0V~some lower than 12V amount too, so be careful. (Like 0V to 10V or 5V)

I have some concern however since there is little reason to have M+ and M- and a tach signal if indeed the speed control is included in the motor. I believe you may be mistaken about that. Those particular labeled connections would normally be going to a motor controller that needs to see them.

But, just to make it go may work by supplying power to the M+ and M-. One polarity forward one backward.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Brushless DC motor question

It's fairly likely that this is a part of a bigger control system which monitors whether things are happening when they are supposed to; e.g. they supply a voltage to the "control" (an output of the bigger control system, an input to this little motor controller), and then they monitor for the feedback of the "tach" signal, and then take some sort of corrective action in the event of a fault (which could simply be a matter of tripping a fault code that a scan tool could then then read, when the customer comes in complaining "My cooled seats aren't working" and the mechanic hooks up the scan tool to the car, which is seemingly the only thing they know how to do these days).

RE: Brushless DC motor question

Thank you for the notes. I will try battery power to M+ and M-, and non-zero volt to Control. If the fan doesn't spin, I will gut out the motor and attach a 12V computer cooling fan to the squirrel cage.

RE: Brushless DC motor question

Most 12V PWM fans use 5V maxim voltage on PWM line control.
Add a resisitive voltage divider to have 5V on control pin for maximum speed.

RE: Brushless DC motor question

The OP stated a brushless DC motor. That will have a three phase inverter in the control circuit.

"Why not the best?"
Jimmy Carter

RE: Brushless DC motor question

!! You're right! I always miss pertinent data listed in the title. I learned never to do that.

Keith Cress
kcress - http://www.flaminsystems.com

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