From: thomas@teecs.UUCP (Randall Thomas)
Date: Thu, 13 Jun 1991 12:44:48 GMT
Subject: Re: DC Motor Controllers
Message-ID: <28960001@teecs.UUCP>
Organization: Litton Systems, Toronto ONT
Path: utzoo!censor!teecs!thomas
Newsgroups: comp.robotics
References: <1991Jun3.220425.12281@osceola.cs.ucf.edu>

To make an 'H' bridge driver with MOSFETS at 24v DC is really simple.

Since you didn't say what is the incoming signal(s) I will try and
second guess.


                               B+ (24vdc)
Typical 'H' bridge             |
using MOSFETS                  |
                  ----------------------------     
 D=drain          |                          |
 S=source         |                          |
Gx=gate           D                          D
             --aG                              Gb--
FETS:             S                          S
  IRFZ20          |                          |
  IRFZ30          -----------(M)--------------
  IRFZ50          |                          |
                  D                          D
             --cG                              Gd--
                  S                          S
                  |                          |
                  |                          |
                  ----------------------------
                               |
                              GND

To controll the gates of the fets

  24vDC-----10K-------------------------------------------
                 |                |                      |
               Zener              |                      |
              17-19v              |-10K-G(ad)            |-10K-G(bc)
                 |                C                      C
               GND          I1--B                  I2--B
                                  E                      E
   Transistors:2N3904 OR          |                      |  
               2N3906             ------------------------
                                           GND
transistor selection depends on which way your logic works but
BOTH trnasistors should be the same in most cases.

A typical "simple" control cct.

Direction -----------(DIR)--Inverter(7404)------(*DIR)

Enable---------------------NAND--------4.7K---------->I1
        |            DIR--/
        |
        |------------------NAND--------4.7K---------->I2
                    *DIR--/

logic:           Enable   Direction   Motor
                   L         X          stoped
                   H         L          CW
                   H         H         CCW
note:in this config when motor runs it runs at max power and max speed.
     To change this requires a "chopper" freq. on the Enable line.

It is also a nice idea to add 2 caps on the gate of the Fets to ground
This will a give a 'ramp' up to speed depending on values.
 
Have fun and good luck.

_______________________________________________________________________________
:                  uucp:  {censor|lsuc|tmsoft}!teecs!thomas                   :
:             All I ask is a tall ship and a star to steer her by.            :
:Randall Thomas        May the winds be at our back.    Toronto,Ontario,Canada:
:_____________________________________________________________________________: