Re: Thank you all [TANKS]

[Frank Pittelli <frank-at-rctankcombat.com>]

Carla and Joe Devine wrote:
> Also a question for Frank P.. Could you summarize the function of the 
> H-bridge that uses mosfets? I kind of get it but not all that well.

There is a detailed explanation of H-bridges at:

        http://www.rctankcombat.com/articles/speed-control

Essentially, an H-bridge is an arrangement of "single-throw" switches 
that can be used to change the direction of a motor.  When two of the 
switches are activated, the motor goes in one direction, when the other 
two are activated it goes in the other direction.  (The MAG speed 
control is basically the same as an H-bridge, except that it uses two 
"double-throw" switches, instead of 4 single-throw switches.)

FETs are basically a silicon switch (no moving parts) that can be turned 
on and off very rapidly.  When FETs are used in an H-Bridge arrangement, 
you can not only control the direction of the motors, but also the speed 
of the motors using Pulse Width Modulation (PWM).  That is, turning the 
FETs on and off at a variable rate to control the speed of the motors. 
If you're not controlling an H-Bridge with a micro-processor, you'll 
need some extra circuitry to make sure that only the proper FETs are 
turned on at the same time.  Otherwise, you'll create a dead short 
across the battery, which lets out all the magic smoke from the circuit.

        Frank P.