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bkonk 07-05-2012 06:14 PM

Relay wiring
1 Attachment(s)
I have an omron LY2 12vdc acting as a relay for a projector screen. The schematics for the relay I crudely drew out in the attachment below. From the projector is a 4 wire power cord, to the wall is a 3 wire, so I end up with an extra red wire. I have two wires connecting to a unit which when powered should activate the relay...I believe these wires connect to 7 and 8 on the relay, but past that I am not really sure what plugs into where. So there is the Black, red, green and white from one end, and black white and green on the other. Any help would be great, thank you.

micromind 07-05-2012 07:28 PM

Need a bit more info here; the 4 wire cord is pretty easy to figure out, but does the 3 wire cord coming from the wall plug into an outlet or does it go to the screen?

Where the 3 wire cord goes makes a huge difference as to how it connects to the relay.

Also, are there any splices in the relay box, or did every wire go to a terminal on the relay? And did any wire go to more than one terminal on the relay?


bkonk 07-05-2012 07:58 PM

the 3 wire cord goes to an outlet, other end is just cut wires which were originally attached to the relay. So screen to relay is 4 wire, relay to outlet is 3 (not sure why the switch to 3 but thats what I'm working with). No splices on the relay box, and I don't think any wire went to more than one terminal on the relay. two wires (I'm guessing from 7 and 8) went to a stereo which activated the relay.

micromind 07-05-2012 09:45 PM

Ok, sorry for asking for even more info, but there are several ways this can be connected.

Is the 3 wire cord is just a basic cord plugged in to a basic outlet? And the outlet has power; it's not the feed to the screen, correct?

The 4 wire cord goes to the projector, correct?

And there's another two wire cord that goes to the stereo, correct? (This one throws a curve at us).

Is the relay plugged in to a socket?

Is there a jumper wire from 4 to 5 on the relay? And another one from 3 to 6?

Do you have a meter that can measure 12 volts DC, and resistance?

It might take a few more posts, but we'll get this figured out....


Jw101106 07-06-2012 03:15 AM

The outlet is a 120 volt A.C. supply so there must be some kind of power supply which turns it into 12 volts d.c. Is the power cord going to some kind of power supply unit, or straight to the relay? I would think that the 3 wires from the outlet supplied power to a power supply unit, and the 4 wires possibly were hooked to the relay.

bkonk 07-06-2012 07:04 AM

Yes the 3 wire is just a basic cord into a basic outlet, outlet has power. the 4 wire is the feed into the screen. There's another 2 wire that goes into the stereo (dc 12v trigger out 150mA MAX), when the stereo is turned on this should ideally activate the screen. The relay itself is not plugged in to anything besides the stereo and two cords. I do not have a meter. It looks like there are jumper wires from 5 to 1 and 6 to 2. (the jumped wire is connected to a copper sheet with a ball on the end that looks like it could shift the connection from 5-1 to 5-3 and from 6-2 to 6-4).

bkonk 07-06-2012 07:18 AM

1 Attachment(s)
picture of the relay

J. V. 07-06-2012 09:46 AM

The drawing looks like a Chinese love letter.

curiousB 07-06-2012 09:54 AM

Looks like a simple DPDT relay to swap the DC voltage across the motor for up and down motion. The relay coil is 7 and 8.

Not clear what is driving this as this is just part of the story. This relay will only set direction of travel. There must be some other relay or switching device to control up and down.

There are probably limit switches buried in the screen as well to stop excess travel in either direction.

Jw101106 07-06-2012 10:58 AM

relay troubleshooting
relay looks like 5-1 and 6-2 are normally closed contacts, and 5-3 and 6-4 are normally open contacts. 7 and 8 are the coil terminals. Check for voltage across the coils, and then check with a multimeter to see if the contacts change state (the open contacts close and the closed contacts open). If they haven't changed state with the coil voltage present, then the relay is probably bad. You'll need a multimeter for this, by the way. Terminal 5 and 6 on the relay are the commons (the power is fed from 5 and 6 for the contacts and when the relay "changes state" the power is sent from either 5 to 1 or 5 to 3, and from 6 to 2 or 6 to 4). I hope this all helps. Let me know if I need to clarify a bit. Try troubleshooting relay with only wires hooked up to the coil, all other wires disconnected.

DangerMouse 07-06-2012 11:45 AM


Originally Posted by J. V. (Post 959164)
The drawing looks like a Chinese love letter.

I showed it to a Chinese girl at the college and she slapped me!


micromind 07-06-2012 08:36 PM

Without a meter it's going to be nearly impossible to get this to work.

About all I can tell from the info provided so far is that most likely the two wires from the stereo go to 7 & 8, and the black wire of the 3 wire cord goes to either 1 or 2.

The white wire of the 3 wire cord could splice to one of the wires of the 4 wire cord, or it could go to 1 or 2, whichever the black wire is not on.

The green wire of the 3 wire cord is a safety ground. It may or may not splice to the green wire of the 4 wire cord. If the box the relay is in is plastic, the green wire might not go anywhere.

The meter is needed to test the 4 wire cord. Without it, we're just guessing which wires do what.


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