Tilden H-bridge

I've built a Tilden H-bridge and now it only goes in one direction. Can anyone help?
Eljin

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try this website http://www.commlinx.com.au/schematics.htm
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Eljin wrote:

I'm intending to fix it so I can build more of the same type.
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Eljin wrote:

That circuit is wierd. The input waveform is fed to the "direction" pin.
See the truth table in the data sheet
http://www.national.com/ds/LM/LMD18200.pdf
to see what's going on.
The duty cycle of the input waveform is supposed to control the speed and direction. 50% duty cycle is stop. > 50% is forward.
It's a power hog, drawing full power when stopped. Not suitable for battery driven applications.
                John Nagle
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