trouble with lutron grx av controller...need opinions

[Dg01501]

Ok so here's the dilema...I'm working in an auditorium and I had to relocate an existing lutron controller up into a ceiling. This controller is for motorized shades. Everything was working before hand. If you check the specs. Link below. The outputs are the terminals that I'm using to do this. All wires were labeled and put back together the same way upon relocating...I have an external transformer putting 28 volts to the common of the output strip and the other leg of the transformer goes to 2 external relays that are used to control the shades going up or down...the other sides of the coils on the relays hit outputs 1 and 5. After hooking it up and turning on the breaker for the tranny. I noticed a hum. The relays were humming. After testing I found out that there was 5 volts coming out of all the output terminals. But only when the transformer was attached to the lutron controller. The shades work fine but I can't get this hum to go away and I don't know why its there! There shouldn't be 5 volts on the outputs. There are leds that light up when the outputs are in use. Yet none of them are lit when I get this random voltage. Also when the output is active I only get 15 volts...shouldn't I get 28? I found another lutron controller and wired it up and it did the same. thing so I'm baffled as to what the problem is....any help would be appreciated. http://Asia.lutron.com/grafikeye/specs/grx-av.pdf

 

[grich]

Is the external 28v transformer the same that was in use before the move? If it's new, perhaps it's undersized.

Is the transformer output getting pulled down when it's connected to the controller? Might still have something miswired.

 

[Dg01501]

no its the same transformer and no the voltage isnt getting pulled down, its puzzeling. could it possibly just be an old worn out controller? i mean i tried two of them but i guess theres always a possibility that there both just junk....there discontinued.

 

[hbiss]

Looks pretty straightforward. If you are sure you have it wired correctly (1&5 on the outputs not the inputs) then the only way the outputs can have a "leakage" voltage on them is because of the controller. You have tried disconnecting everything except the transformer and the two outputs going to the relays and you still get the hum and 5 volts, right?

-Hal

 

[grich]

Just looked at the spec sheet...the controller is using open-collector outputs, and you have external relays controlling the load. You need 28V DC, with the negative side of the supply connected to the C terminal, and the positive side tied to one side of the relay coil. I would check to see how clean the DC is, or if it's DC at all. I've had more than one wall-wart lose it's filter capacitor after cooking away for years.

 

[hbiss]

Good work! I assumed the OP knew what he was talking about and based my diagnosis on a transformer (AC) and dry contacts in the controller. This all goes to show that you really have to understand what you are working with. A little observation as to what it says on the "wall wart" and knowing how to use a VOM to measure AC and DC voltages should have made it clear that it was not a transformer at all but a DC supply. If he would have said that in the beginning it would have been obvious that it was causing the problem and needed replacement.

-Hal