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H-Bridge Debugging — Parallax Forums

H-Bridge Debugging

ArchiverArchiver Posts: 46,084
edited 2003-10-30 12:26 in General Discussion
Good Morning-

Long time listener first time caller... I'm trying to debug a H-Bridge
circuit I just built (standard h-bridge,
http://www.solarbotics.net/library/circuits/driver_tilden.html)

Basically it doesnt work. To test it I wrote a program:

start:
LOW 1
HIGH 0
PAUSE 1000
LOW 0
HIGH 1
PAUSE 1000
goto start

to switch between power on one side and the other. This should manifest
itself in the motor switching directions. Rather, it just chugs forward.
Also, my 3.6v AA battery pack wont power the motor (which it does straight
up connecting it).

The only difference I have between the listed circuit and my own is no
resistors... but this shouldnt change the properties of the circuit.

Using a voltmeter, I verified the output of pin 0 and 1. I also checked
the inputs to the bridge, they were nominal. Testing the motor outputs of
the bridge revealed a constant voltage, consistent with the motors going
full boreforward, but it should be flip-flopping every second.

Any ideas?
Thanks
Phil

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-10-29 17:14
    for H bridge conrol and circuitry along with some sample code, check out
    http://www.geocities.com/jimforkin2003/
    jim
    Original Message
    From: Philip Hahn [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=nWaGBqdbW2icMA2pywXvGwX05mx0cuHqBaeVny6rBl2p3CQWoxfFlXYuAZYgAh1QJMjwmdwHHw]phil@n...[/url
    Sent: Wednesday, October 29, 2003 4:42 AM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] H-Bridge Debugging


    Good Morning-

    Long time listener first time caller... I'm trying to debug a H-Bridge
    circuit I just built (standard h-bridge,
    http://www.solarbotics.net/library/circuits/driver_tilden.html)

    Basically it doesnt work. To test it I wrote a program:

    start:
    LOW 1
    HIGH 0
    PAUSE 1000
    LOW 0
    HIGH 1
    PAUSE 1000
    goto start

    to switch between power on one side and the other. This should manifest
    itself in the motor switching directions. Rather, it just chugs forward.
    Also, my 3.6v AA battery pack wont power the motor (which it does straight
    up connecting it).

    The only difference I have between the listed circuit and my own is no
    resistors... but this shouldnt change the properties of the circuit.

    Using a voltmeter, I verified the output of pin 0 and 1. I also checked
    the inputs to the bridge, they were nominal. Testing the motor outputs of
    the bridge revealed a constant voltage, consistent with the motors going
    full boreforward, but it should be flip-flopping every second.

    Any ideas?
    Thanks
    Phil




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  • ArchiverArchiver Posts: 46,084
    edited 2003-10-29 18:14
    --- In basicstamps@yahoogroups.com, "Philip Hahn" <phil@n...> wrote:
    > Good Morning-
    >
    > Long time listener first time caller... I'm trying to debug a H-
    Bridge
    > circuit I just built (standard h-bridge,
    > http://www.solarbotics.net/library/circuits/driver_tilden.html)
    >
    > Basically it doesnt work. To test it I wrote a program:
    >
    > start:
    > LOW 1
    > HIGH 0
    > PAUSE 1000
    > LOW 0
    > HIGH 1
    > PAUSE 1000
    > goto start
    >
    > to switch between power on one side and the other. This should
    manifest
    > itself in the motor switching directions. Rather, it just chugs
    forward.
    > Also, my 3.6v AA battery pack wont power the motor (which it does
    straight
    > up connecting it).
    >
    > The only difference I have between the listed circuit and my own is
    no
    > resistors... but this shouldnt change the properties of the circuit.
    >
    > Using a voltmeter, I verified the output of pin 0 and 1. I also
    checked
    > the inputs to the bridge, they were nominal. Testing the motor
    outputs of
    > the bridge revealed a constant voltage, consistent with the motors
    going
    > full boreforward, but it should be flip-flopping every second.
    >
    > Any ideas?
    > Thanks
    > Phil


    Add pull down resistors on the signal lines.

    Also transistors will need enough current on the base to allow power
    thru them. since you want them staruated, check the Hfe and make
    sure you are providing enough power.

    This can be tested by monitoring the voltage on the base of the PNP
    and NPN units that are activated and verifying zero on the base of
    the ones not.

    possibly add pull down resistors on the base of the PNP and NPN as
    well.

    Dave
  • ArchiverArchiver Posts: 46,084
    edited 2003-10-30 12:26
    Hi Phil,

    I wasn't sure what the current your motor uses and which transistors
    you are using.

    the 3904/6 are typically 100mA, with some at 200ma. If your motor is
    still slow, the motor may not be getting enough current.



    Dave



    --- In basicstamps@yahoogroups.com, "Philip Hahn" <phil@n...> wrote:
    > Good Morning-
    >
    > Long time listener first time caller... I'm trying to debug a H-
    Bridge
    > circuit I just built (standard h-bridge,
    > http://www.solarbotics.net/library/circuits/driver_tilden.html)
    >
    > Basically it doesnt work. To test it I wrote a program:
    >
    > start:
    > LOW 1
    > HIGH 0
    > PAUSE 1000
    > LOW 0
    > HIGH 1
    > PAUSE 1000
    > goto start
    >
    > to switch between power on one side and the other. This should
    manifest
    > itself in the motor switching directions. Rather, it just chugs
    forward.
    > Also, my 3.6v AA battery pack wont power the motor (which it does
    straight
    > up connecting it).
    >
    > The only difference I have between the listed circuit and my own is
    no
    > resistors... but this shouldnt change the properties of the circuit.
    >
    > Using a voltmeter, I verified the output of pin 0 and 1. I also
    checked
    > the inputs to the bridge, they were nominal. Testing the motor
    outputs of
    > the bridge revealed a constant voltage, consistent with the motors
    going
    > full boreforward, but it should be flip-flopping every second.
    >
    > Any ideas?
    > Thanks
    > Phil
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