Re: I need a latching relay...or do I?

Hi,

I think you can do what you need with an ordinary relay if it has a
spare pole. Try this:

1) Connect the spare NO pole in series with your relay coil.
2) Connect your foot pedal NO switch in parallel with the relay NO
pole.
3) Connect the NC limit switch in series with the relay coil.
4) Place the whole mess across your AC line.

What will happen is when the foot pedal sw closes, the relay will
close. Its spare NO pole will close, sustaining coil current even if
you release the pedal. It will run the ram until it hits the NC limit
sw, which will break coil current because it is in series, dropping
out the relay.

Mariss

--- In CAD_CAM_EDM_DRO@y..., dougrasmussen@c... wrote:
> Group,
>
> I think I need a dual coil latching relay. Checked with Grainger
and
> they don't have the 120V model I'd like so I need another source.
>
> Here's the project...I want to advance and retract a hydraulic ram
> with the motion initiated by momentary contact of a foot switch.
My
> hydraulic pump has a 120V solenoid valve with two solenoids. Call
> them A for advance and R for retract.
>
> Hook the latching relay to A so it's latched on foot switch
contact.
> The ram advances until it hits a limit switch which will un-latch
> coil and de-energize A, then ram motion will stop. The limit
switch
> will be ganged with another one which will simultaneousy latch the
> the other relay coil controlling R which will cause the ram to
begin
> retracting. When the ram retracts to it's start position it'll hit
> another limit switch which will un-latch the relay's R coil.
>
> Make sense? Seems simple enough or has anyone got a better idea?
> Part numbers for dual coil latching relays? Grainger has their own
> brand relays (around $12) so it may be less expensive to buy two of
> their single coil units instead of trying to get a more expensive
one
> from someone like Potter-Brumfield.
>
> Thoughts?
>
> thanks,
>
> Doug