[EMS Discuss] HIgher current H-Bridge and circuit help

Taper Wickel EMAIL HIDDEN
Sat Apr 6 11:47:54 PDT 2013


Whoops, yes.  I missed that, thinking that there was a center OFF like your
switch. So yeah, switching the motor Vcc (probably with a second relay)
would be your off condition.

Taper.

--
Taper Wickel <EMAIL HIDDEN>
On Apr 6, 2013 11:40 AM, "Cord Slatton" <EMAIL HIDDEN> wrote:

> That sounds almost perfect, but from the description on the DPPT relay
> link you posted the motor will always rotate with one of those, the circuit
> I built stops it based on input from switches and it needs to be stopped
> most of the time...I can cut power to the vcc of the DPDT relay to stop it
> from turning I guess...
>
>
> On Sat, Apr 6, 2013 at 11:12 AM, Taper Wickel <EMAIL HIDDEN> wrote:
>
>> My quick reaction is to go with relays -- and on consideration, that
>> original switch is probably just a DPDT wired with each "throw" inverted.
>>
>> Er, reading that back, maybe this page will make things clearer:
>>
>>
>> http://www.engineersgarage.com/electronic-components/dpdt-double-pole-double-throw-relay
>>
>> What you lose, compared to an H-bridge, is the capacity for speed
>> control, but in this application it doesn't sound vital.
>>
>> Hope this helps!
>>
>> Taper.
>>
>> --
>> Taper Wickel <EMAIL HIDDEN>
>> Hi all!
>>
>> I hope someone may be able to help me to decide what direction to take a
>> project that semi-works but doesn't complete the goal set out.
>>
>> I have a chicken door opening mechanism built using an electronic
>> screwdriver powered from 4 AA batteries, it has a spool on the driver area
>> and it winds up a rope that pulls up the door through a pulley system. The
>> switch on the screwdriver is a weird type that throws both negative and
>> positive at once and then reverses that for the other direction, thereby
>> avoiding the need for any IC or control. The way we operate it is to hold
>> the button while the door goes up or down and release it when it is in the
>> correct spot. This all works fine and has been in place for a while.
>> However now that it gets light earlier I have built a circuit that will
>> automatically open the door when it gets light. It uses an H-Bridge to
>> control the motor instead of the direct connection to the batteries as
>> before, which worked great in testing with a motor with no load on it,
>> however once I built it all and tried to put it in place the current of the
>> H-Bridge(600ma) was not enough to open the door at more than a snails pace.
>> My question is: should I continue to look for another higher amperage (to
>> let all the juice from the batteries through would be a much higher
>> amperage, like 1 amp)H-Bridge with a similar pinout layout or try to use
>> relays to switch it, or try to use some transistors to do it?
>>
>> Thanks for any help!
>>
>> Cord
>>
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>>
>
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