RE: [CAD_CAM_EDM_DRO] I need a latching relay...or do I?

I did something very similar to this for a chain puller with a $110 PLC
from www.automationdirect.com. ( Unfortunately the programming software and
cable cost another 140 bucks.) They also have $10 mini DIN limit swithes.
More expensive than your relays though. Andy Olney

-----Original Message-----
From: dougrasmussen@... [mailto:dougrasmussen@...]
Sent: Thursday, April 26, 2001 4:48 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] I need a latching relay...or do I?


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


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