How to connect PWMPAL to an h-bridge

Steven

We have just purchased the PWM-PAL chip, and everything seems to be working great. Our only problem is that we wanted to connect it to our H-Bridge circuit. The H-Bridge that we are using is the one at www.bobblick.com under projects under H-Bridge. He says that once you have the PWM circuit working then you can control the H-bridge.

The documentation that you guys sent to us for the PWM_PAL only gives code for a particular setup. We would like to know how to connect our H-bridge to the BS2 Stamp and PWM_PAL.

Thanks

Steven·

Beau Schwabe

Looking at the H-Bridge schematic, and for that matter MOST H-bridge schematics, the main thing that you MUST watch out for is that the
two inputs NEVER both go high at the same time or you will let the smoke out of the H-Bridge. For this reason, this is why I like to use
a dual OPTO-ISOLATOR configured in a way that will make this condition impossible. You can see this configuration on a previous post...

Image reference
Thread reference

There are a couple of ways depending on your application where you can introduce your PWM signal to control speed.
One is to provide a differential PWM signal (180 deg out of phase) to the A and B inputs of the H-Bridge.
A second is to apply the PWM signal to a MOSFET or bank of parallel MOSFETS in series with the POWER to the
H-Bridge and use the A and B signals on the H-Bridge as DC control lines to select the direction.

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Beau Schwabe - Mask Designer III

National Semiconductor Corporation
(Communication Interface Division)
500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071

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Tom Walker

Beau,

I said pretty much the same thing in the last post about this, but for future reference, the Blick H-Bridge reference docs say that having both A and B high is legit. He uses the extra state for braking.

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Truly Understand the Fundamentals and the Path will be so much easier...