Relay power problem

[halstaff]

I'm trying to use my EZ-8 to trigger a relay and can't get it to work.  The board works great when hooked up to an LED for testing.  I'm using the 12V wall wart that is recommended for the board and am getting 13.71V at the plug.  However I can't get it to fire a relay.  When  I program a long "on" cycle into a channel and put a a meter between V+ (positive) and OUTx (negative), I only get about 9V.
I ordered a new ULN chip and replaced the one on the board and get the same results.  I've tested my relay circuit and it works fine when connected to a fully charged 9V battery.
Any thoughts on a solution?

[JackMan]

Sounds to me like you have an unregulated or bad power supply. With a good 12v PS you should be getting 12v between V+ and OUTx. You should also be getting 12v (or just slightly above) at the plug.

[JonnyMac]

Something is amiss.  I connected a WickLED to an EZ-8 (you need to measure across a load) and got 11.5v when operating with a 12.2v input (which make sense as the load was only about 20mA).

[halstaff]

I got the power supply from EFX that was supposed to be the right one.  I am getting over 13V at the plug but losing over 4V at the output.  Would using a regulated 12V power supply give me the usual drop of around 1V to the output?
Any other thoughts on what to try to fix the problem?  This controller is running several props that lead to my front door where the TOTs come to get the candy.  The main path in my display has been turned into a bunch of static props as I need to control the relays in order to get them to run.

[JonnyMac]

I'm still struggling with "losing over 4v at the output."  When you're measuring at the output, is it with some kind of load connected? (e.g., the relay)

[halstaff]

That may be my problem as I wasn't measuring it under load.  Maybe it's a bad relay after all.

[JackMan]

With 12.2v going in and no load, I get 11.4v between V+ and OUTx. Something is wrong other than your relay. You stated in the first post that your relay works fine when connected to a 9v battery. Although there are exceptions, most 12v relays won't work on 9v. At any rate, you stated your relay works. What's the mA draw of your relay? How many relays do you have connected (or plan to connect) to the Prop-1?

[halstaff]

I'll measure it under load tonight when I get home.
The relay I'm using is a 5A.  I was hoping to use 3 or 4 relays.  Maybe using the EFX relay board will solve the problem.

[JonnyMac]

You need to ensure that the coil current is 200mA (or less) when activated -- that would be about 2.4W.

[JackMan]

The relay I'm using is a 5A.

I think you're confusing the contact rating with the mA draw of the coil. You need to find how much current (mA) the coil of the relay needs to operate.

[bsnut]

Jack has a good pont. You need to find how much current (mA) the coil of the relay needs to operate.

Here's how you find out how much mA the relay coil draws.

1) Connect volt meter in series with the lead on one side of the coil and connect the other lead to other side of the your power supply, then make sure that the other side of the of the relay coil is connected to the power supply. Make sure your volt meter is set on mA. This will tell you how many mA relay coil is drawing.

2) Look at the top of the relay for the manufacture's name and get on there web site, were you should find the data sheet for that relay model.

I done this alot in the 21+ years as an control electrician. As, I say practice makes perfect ;D  

[halstaff]

You're right.  I'm still new to this and trying to make sense of it all.  I'm using a OMI-SS-212D, 12V, 5A relay.  The datasheet is at http://relays.tycoelectronics.com/datasheets/OMI-2P.pdf  If I'm reading it correctly, it's 60mA which is within the range noted.
I checked the EZ-8 with a constant on and the relay attached and it read 13V so I'm thinking this is not a problem with the board but with the relay.

[bsnut]

I would suggest you to try another power supply and I am thinking that the power supply maybe bad. I have one question for you... What is the size(in amps) of the power supply, you are using? 

[halstaff]

I would suggest you to try another power supply and I am thinking that the power supply maybe bad. I have one question for you... What is the size(in amps) of the power supply, you are using? 

I got the power supply from EFX.  It's a 12V 1000mA supply that's supposed to be for the EZ-8/

[bsnut]

What else are you trying to power, besides the relays?

What, I would use is a good relay that you know that works and test with the power supply that came with the EZ8. Once you know it works with that power supply, then I would test the other relays with the EZ8 with a long pulse. Do this test with all same relays to find any bad relays.

Remember when you load down any power supplies, the voltage will drop down to what the power supply voltage is.