I would've thought that the path through the diodes provides braking. Am I misreading that?The schematic in post #44 will not give any braking.
If I need to regulate the braking power would it be ideal to have a 4R 5W resistor in series with M2 and D1 ?Thank you Less.
I've just tested this without the MOSFET and i am pleased with it. The stopping time is very fast with a few sparks on the motor brushes as expected. I omitted the MOSFET circuit and connected ground directly to the supply.
View attachment 167010
Would adding a resistor in series with the M- and the Anode of D1 control the rate at which the motor stops ?
Thanks for the clarification. I thought this EMF had the opposite polarity. So much to learn... thanks for your help!The EMF due to the motor continuing to rotate is the same polarity as the supply so if the diode was conducting with this polarity it would also short out the supply when the motor was running.
Your correct. The Diode had nothing to do with the braking. I was carried away with D1 in the Dremel schematic. So a basic SPDT switch would do the job but need to figure out a way to slow down the braking which is close 20A peak and the inrush current, 50A at 5A steady.anishkgt,
I can't answer your question as the way you have wired your circuit can't be the same as post #44 as that circuit would give no braking. You would need to show HOW IT IS ACTUALY wired. IF it was wired as in post #24 then the resistor would be inserted between contact 1 on the switch and the motor negative. With a value of 4 ohms the INITIAL braking current would be a little less than 3 amps. (12/(4 +Rm) amps Rm is the internal resistance of the motor. You will have to use a high power potentiometer (Or just try different values.) and adjust it until you get the exact stopping time you require.
Comments for ebeowulf17. The path through the diode only conducts with the back EMF due to the inductance of the winding when the power is removed. This is because this is in the opposite polarity to the supply to the motor. The EMF due to the motor continuing to rotate is the same polarity as the supply so if the diode was conducting with this polarity it would also short out the supply when the motor was running.
Les.
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