Re: motor starting and reversing.

On Aug 22, 9:24 am, Austin Shackles
<austinDITCHTHISFORBETTERRESU...@xxxxxxxxxxxx> wrote:
On or around Thu, 21 Aug 2008 22:59:03 +0100, Austin Shackles
<austinDITCHTHISFORBETTERRESU...@xxxxxxxxxxxx> enlightened us thusly:



Hmmm.  could interlock it, it just needs an extra pole in the relays so that
the forward relay, once energised, breaks the circuit for the reverse button
and vice versa.  In fact, might be able to run it through the live terminals
in the DPDT.  I shall study it some more.

A bit more thought and several more bits of paper and I reckon this circuit
does it.

http://www.roman-road.co.uk/temp/DSC00200.JPG

shown in the off state.  The forward start button is fed from the reverse
relay and the reverse start is fed from the forward relay, so that either
will work from rest.

Once it's running forwards, it self-excites through the stop button, so it
latches, and the supply to the reverse start button is interrupted. Pressing
the forward button again has no effect, just connects live to live.

The only thing this one doesn't do is prevent pressing forward and reverse
at *exactly* the same instant.  However, you'd need to be clever as the
relay operating speed is pretty fast.

Just one fly in the ointment now: the box as supplied only has one set of
terminals in the stop button, and my circuit requires 2.  However, there's
scope to add another set if I can get hold of the right one.  Considering
the price, if the bloke has more of them, I could just buy another box and
rob the switch from it.
--
Austin Shackles.  www.ddol-las.net my opinions are just that
Travel The Galaxy!  Meet Fascinating Life Forms...
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Yes. That circuit would work. I'm just a bit worried by the fact
that applying mains to the motor terminals 1&4 when the circuit, as
you posted it last, is in the "at rest" (ie Off state). By this means
you could cook the motor as it will not rotate until either the FWD or
REV button is pushed. Similarly, you'll have to be quick to hit the
main switch as pushing the STOP button will have no effect if the
motor is running.

Not, IMHO, a very safe way of controlling the motor.

BTW. What wattage/hp is this motor ?
.

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