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34459Re: [beam] H_Bridge

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  • Wilf Rigter
    Mar 9, 2003
      I have build and tested the MOSbridge 2 circuit and I am happy to report it
      works well.

      I used 2N3904/6 instead of PN2222/2907 driver transistors, 2.2K resistors
      and some "free" Dpak N channel and P channel mosfets had I liberated from a
      surplus harddisk IDE control board. The motor supply was 12V and the logic
      signals 5V.

      The circuit is quite efficient with PWM 0%-100% up to 5kHz. I briefly tested
      at 50kHz PWM but got significant ringing above 500mA, so I backed off but
      will investigate higher frequencies later. The anti-shoot through circuit
      seems to work well, and from o'scope observations breaks motor current for
      about 5usec before making. The rise and fall times of the winding voltage
      waveforms were a modest 2usec. Surprisingly PWM was most efficient with one
      input grounded. The MOSfet internal diodes were used for freewheeling. No
      heatsinks were used for the MOSfets and the circuit remained cold while
      switching a 1A motor load. The voltage drop was as expected for the device
      Rdson specs. I expect, with better MOSfets, 18V motors and >10A currents
      can be efficiently controlled with this simple circuit.

      wilf

      ----- Original Message -----
      From: "Wilf Rigter" <wrigter@...>
      To: <beam@yahoogroups.com>
      Sent: Monday, March 03, 2003 6:08 PM
      Subject: Re: [beam] H_Bridge

      ---snip----

      my favorite version of all: the general purpose >>> MOSBridge2 <<< design.
      Use logic level MOSFETs for applications requiring up to 9V motor supply.
      Use normal MOSFETs for motor supplies in the 10V - 18V. Higher motor supply
      applications will require some protection of the MOSFET gates.

      High logic level input signals can be anything between 2V to 24V. If
      necesary add a base emitter resistor to the PN2222 to increase noise
      immunity for the low level logic signal.


      enjoy

      wilf



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