Relay power problem

[JonnyMac]

I think you might have a duff power supply.  You should certainly see more that 9.5v on the output, I measured and verified.  And to Jack's point, if a 9v battery can activate the relay, then 9.5v out of the board should... unless it's a bad power supply and under any kind of load goes limp.

[halstaff]

Well I tried another 12V power supply and still nothing.  I measured both power supplies and am getting a good 12V from each at the plug.

[bsnut]

This, is how I would troubleshoot the EZ8.

Do you have 12vdc between V+ and GND when the power switch is set in position 2? If you have 12vdc this means your relays or 12vdc LEDs should work. You need to make sure that the EZ8 isn't touching any conductive surfaces, that could cause the power supply to shut down.   

I suggest you to do this next test, to see if EZ8 ULN is working like it should. This means, you will need delete the old program that you have.

What, I am suggesting you do, is program Channel 0 to be on for 5 seconds or more. This should give you time to put a meter between V+ and Channel 0. If you see 12vdc between V+ and Channel Output 0 with your meter and it turns off after 5 seconds, this means ULN is working correctly.

You will need do this test for all of the channels on the EZ8. That way you can see that all the channel outputs are working correctly. If, you don't see 12vdc on Channel Output 0 or any other Channel Outputs, you will need to replace the ULN with a new one. If you want you can use a relay or a 12vdc lamp when doing the rest of this test.

[halstaff]

Good idea but I've already tried that.  I even ordered another ULN chip from DigiKey and replaced the original one and it still wont trigger the relay.

[JonnyMac]

Keep in mind that a meter applies virtually no load when measuring voltage so this is not a valid stress test.  If you plug 12v into the EZ-8+ and only measure 9.5v between V+ and GND then there is a problem with the board (which should be smoking) or the power supply.

[halstaff]

Fortunately, the boards not smoking and I tried 2 identical power supplies that I got from the order RMG placed for the June gathering.  I've used 2 different ULN chips so that probably isn't the problem either.  I've tried several different relays.  So if it's not the board, power supply, relay or chip that leaves me.  I must be doing something wrong but I don't know what else to try.
Thanks everyone for all the help but it looks like this project will be put off until next year.  I hope everyone has a great Halloween!

[JackMan]

As a last ditch effort try programming two channels of the EZ-8 identically for the relay. Connect both channels to one side of the relay coil and the other side of the coil to V+.

[bsnut]

I was editing my post when you posted what you did.

Are you setting the board on any conductive surfaces? It sounds like to me the power supply is bad or it doesn't have enough mA to do what you want to do.

Jon is right, when measuring voltage, it is not a valid stress test. The goal is to see that the ULN is doing its job and using a 12vdc lamp or relay to do the rest of the test was a way to test without a meter.

I, would suggest you order a 12vdc @ 1000mA plug in power from Jon and its sized for what you need to do.  

[halstaff]

I have 2 power supplies that I got from Jon that are supposed to be for the EZ-8 and I'm not having any luck with either of them.

[halstaff]

As a last ditch effort try programming two channels of the EZ-8 identically for the relay. Connect both channels to one side of the relay coil and the other side of the coil to V+.

I thought that might work but still nothing from the relay.  I guess I better not get in any disagreements with kids as I'm certainly not smarter than the 8 year old that was able to make this work.

[bsnut]

I am wondering what is the no load voltage(open circuit) of your 12vdc power supply is? 12vdc plug in power supplies, put out around 15vdc in open circuit for a 12vdc power supply.

My, thinking is that the power you have is mismarked from the manufacter and you will never know untill you power it up with a load and check it with a meter. If it is a 9vdc power supply, they put out around 12vdc in open circuit for a 9vdc power supply.

I do not understand, you are saying it is not ULN and I can't see why are having problems. I only blue smoked one pre EFX-TEK product the RC4 and that is because I hooked up the servo cable wrong ;D. I shorted power supplies before and they just shut down and when I remove the short the power supply returns to normal.  

[JackMan]

Take a voltage reading at the relay coil connections when the EZ-8 is running the program and the relay should be energized and let us know what you find. If you are getting 9.5v at the relay coil, I'm stumped as to why its not pulling in if it works with a 9v battery.

[halstaff]

Alright, since you guys refused to give up on this, I continued on and have solved one mystery.  I put my meter on the 9V battery when connected to the relay and was getting a reading of over 15V.  Now I enough to know that's not right.  Changed out the battery in my meter and low and behold I get a reading slightly above 9V, right where it should be.  So I reconnected the relay and ran the steady state program to get a good reading and am only getting 6.4V.  I apologize for such a newbie mistake which resulted in bad info.  No way can I expect you to help solve the problem if I give bad numbers.
However, that still doesn't solve the problem of the relay not operating with the EZ-8.  I've tried 3 different relays, 2 power supplies and 2 ULN chips.  I've connected the relay both in NO and NC positions with no change. 
I tested the relay with some partially depleted 9V batteries and found it won't work with 7.85V but will with 8.5V.  If I now have the readings right, the problem seems to lie in the fact that I'm only getting about 6.4V to the coil of the relay when attached to the EZ-8. 
What am I overlooking?  And where's that 8 year old so I can have him show me what I'm doing wrong now?
Steve

[bsnut]

And where's that 8 year old so I can have him show me what I'm doing wrong now?

So you want 8 year old to program and troubleshoot it. I think Jon charges extra for that ;D.

When, I troubleshoot control system at my work or at home, I start at the beginning. And that is the incoming power supply. I will check to see if the voltage is right. In your case, a 9 volt battery doesn't have a enough mA to run your relay. That is the reason why the battery voltage is down to 6.4 volts, that because the coil and EZ-8 voltage requlator is causing voltage drop. That's why the plug in power supplies voltage stays around 12 or 11.5 volts, because of the voltage requlator in the power supply keeps the voltage up. Then, if the volage isn't right then I start disconnecting each load (relay or light) one it a time to find the problem.

I don't know why you are using a battery to do your test. This is only good for programming the EZ-8.

We are trying to help fellow prop builder out and I don't like to give up. This also provides useful info to other prop builder to learn from. I will try the relay setup that you have, so I can see what is going on when I get home from work.

[halstaff]

Well due to the fact that you guys were still trying to figure this out long after I had given up, it's fixed.
I had been using the 2 power supplies I had gotten from Jon that were for the EZ-8 and were marked at 12V, 1 amp.  When I put them under load and checked the reading on the back of the board, they were both only showing 7.5V.  Either they are both faulty or mismarked.  I was able to pull a regulated 12V power supply from another prop and presto, it works.
Lessons learned - it's better to trust a reliable meter than to make assumptions or believe a label.  Also, haunters are the best!
Thanks for all the help and persistence in helping me figure this out.   Now it's time to let my inner 8 year old out to get this programed and ready for Halloween.  Good luck to everyone with your haunts!
Steve