Alt-BEAM Archive
Message #11867
To: beam@sgiblab.sgi.com beam@sgiblab.sgi.com
From: Ben Hitchcock beh01@uow.edu.au
Date: Wednesday, March 15, 2000 5:30 PM
Subject: Re: H-Bridge
>Take two NPN transistors, and connect their emitters to ground.
>
>Take two PNP transistors, and tie their emitters to +Vcc.
>
>Connect the collector of NPN1 to the collector of PNP1, and attach the
>positive terminal of your motor here.
>
>Connect the collector of NPN2 to the collector of PNP2,
>and attach the negative terminal of the motor to that point also.
>
>Now attach 1k resistors to all the four base terminals.
>
>Connect NPN1 and PNP1 via their base resistors. Where the two resistors
>join, call this bias point 1.
>
>Connect NPN2 and PNP2 via their base resistors. Where the two resistors
>join, call this bias point 2.
>
>Now treat bias point 1 and bias point 2 as a motor. Both high or both low
>and nothing happens. one high and 2 low, it spins one way, but reverses
>if you swap polarities.
>
>Note that this should ONLY be driven by logic gates, not analog circuitry
>because if the bias points are halfway between the supply rails then you
>will let the smoke out.
>
>+v-------o-----------------o----
> | |
> P P
> +-1k-n n--1k-+
> | p p |
> | | | |
>BP1o o-----Motor-------o o Bias Point 2
> | | | |
> | n n |
> +-1k-p p--1k-+
> N N
> | |
>0V-------o-----------------o---
>
>
>
>> I seem to be having trouble with a smokless non latching H-bridge
>> everything i have tried resulted in either a latching H-Bridge or
>> when both inputs were pulled either high or low the bridge would
>> short :(
>>
>> Any thoughts?
>>
>> I was trying out W.Rigter's Smokless latching 4 transistor H-Bridge
>> and remover the 2 resistors that supply the latching current but for
>> some reason that did not work either :(
>>
>> Regards
>> Andrew
>>
>
>
>--
>Nothing is foolproof to a sufficiently talented fool.
Home