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Have an AC operate like a DC

4130 Views 1 Reply 1 Participant Last post by  T-Man
Now I have a handle on the reversing circuit, the next question is how to apply it to an O scale AC engine. Using the DC engine is easy but what to do with AC can be done. So far I have worked out a theory. No e unit is necessary and the trick is using a bridge rectifier on the magnetic coil for the engine. This will guarantee a uniform polarity when the power is reversed. Then you connect each motor brush, one to ground, one to center rail. Hopefully by switching polarity on the rails the motor will go forward and reverse.
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The Lionel post war motors run on AC. Years ago the bridge rectifier was the size of a boxcar. Now by adding a new one the motor wll operate on DC. Today the DC can motor is used. Technically it always could but we want to use a DC transformer and reverse the engine by reversing polarity. With out the bridge the engine will always go in the same direction. Since the coil is grounded.

This diagram ensures the coil has a consistent magnetic field when the polarity of the track changed. Normal DC motors do not have the porblem since they use magnets.

The bridge rating was small an 8 amp rectifier is needed
I tested a 1062 and gave up, Too much heat for the rectifier.
The Radio Shack number is on the right, for the Bridge.


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