need help with dc motor controller using spst momenrary button.

Started by Sweetie Pinellas November 6, 2015
Sweetie Pinellas wrote:
> > > I am looking for a way to control two SPDT relays configured=20 > in a ground common configuration like in the link below,=20 > which will control the motor in three states. Normally it > would use a SPTT toggle, but I want to have it operate on=20 > momentary spst push button. Push and hold it and motor turns > clockwise, release and it stops, press again an hold it and > motor turns counter-clockwise, and so on.
** DC motors do not take kindly to having the polarity reversed when spinni= ng at high rpm and your proposed set up allows this to happen. Sudden rever= sals cause very large current surges that burns brushes and commutators. Th= e damage is made worse if the motor has any kind of flywheel device attache= d- ie a prop or fan blade. The motor should be made to stop before polarity reversal occurs, which mig= ht involve dynamic braking by applying a short or low resistance across th= e motor's terminals for a sufficient time. .... Phil