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Russell Bull
08/20/05 07:50
Read: 937 times

#99729 - DC injection
Responding to: Shivani Saini's previous message
You don't want to stall a running motor - you want to stop the motor quickly! The usual solution is to have an electromechanical brake. The electromagnet removes the brake when power is applied and a spring operates the brake when the power is removed.

The other method is to half wave rectify the mains (with a suitably sized diode) and switch this to the motor. This is called 'dc injection'. You need to limit the time this is activates as well as limiting the current. Done properly, this will stop the motor in short order. Since you're asking this question and this implies you have little experience in this area, I would suggest you avoid doing this - there is much smoke to be had if you get it wrong. Please don't ask for a circuit - there are many variables involved - get an experienced engineer to design this for you!

I would suggest that you have two options:

1/ get an electromechanical brake.

2/ use a variable speed drive. These usually have DC injection and the variable speed feature will help in acceleration and deceleration of the motor. These are around $300USD for <1Kw. With one of these, all you micro has to do is tell it either forward or reverse - you can set the accel/decel times, speed etc. I use this method for a display board rotator. Works well for me.

List of 4 messages in thread
how to stop running motor      Shivani Saini      08/20/05 01:06      
   DC injection      Russell Bull      08/20/05 07:50      
      DC injection is FUN      Steve M. Taylor      08/20/05 08:43      
      DC Motor?      Andy Neil      08/22/05 10:38      

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