> I don't remember who it was who suggested this before, but I liked 
> the idea
> of using the brake FETs in the bridge and getting the brake effect 
> "for
> free". Did you check out that circuit?

I've looked at it but haven't yet breadboarded it. Because of the way 
the motor behaves its VERY advisable to try ideas in real world 
situations.Simulations and theory can let you down badly here.

You may recall the discussion a few weeks ago where various in bridge 
ideas were tried. My first design applied regulation to the bridge 
proper. The ideal design would integrate bridge, voltage regulator and 
brake. In many designs the need for a near zero quiescent current 
makes life harder.

One issue with having the FET's in the bridge proper is the need to 
turn them on only AFTER the drive is removed and while the top half of 
the bridge is powered off. This isn't hard but adds to circuit 
complexity. Something like what I have done to turn on the FETs now 
would probably work. Having the motor provide drive to its brake 
transistors (bipolar or FET) is an obvious idea as it's potentially 
self controlling. I tried back to back transistors which 'reached 
across the motor' for their base drive. All such schemes so far are 
either less than ideal brakes and/or require extra control circuitry. 
TANSTAAFL seems to apply thoroughly here.

A good thing about the FET circuit that I have so far is that it works 
well and is essentially independent of other interactions. I can 
control its braking effect, attack time and on time easily and 
quiescent current is essentially zero.

I'll happily use a simpler / cheaper design if it's as effective (or 
even good enough). I'll probably be playing with some of the ideas 
suggested in the next few days.


        RM

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