Power for relay module

[midway27]

I'm thoroughly stumped. I've spent 4+ hours troubleshooting and browsing the internet to no avail.

My BCS is powered with 9 volts, and I have my relay module powered with 5 volts. I'm sharing the ground between the BCS and relay module, and I can activate the relay module just fine with the outputs from the BCS, but when I turn off the outputs from the BCS, the relay remains on.

I've also powered the relay module temporarily with the +5v output and ground from the BCS. When I do this, cycling the BCS outputs on/off works flawlessly to activate/deactivate the relay module. I do not want to continue powering the relay module with the BCS for fear of frying the BCS...

Does anybody know what could be going on?

[JonW]

Do you have any specs or a link for the relay?

How about a pic or drawing of the wiring?

Have you tried a meter on the BCS output and checked if the voltage goes on and off when you activate/deactivate the output?

[midway27]

Here is a link to the relay that I am using. It is set-up active high.

http://www.ebay.com/itm/261712362026?_t ... EBIDX%3AIT

Attached is a diagram of what I've been troubleshooting with.

The voltage has not been going on/off when I activate/deactivate the output (when the relay is powered from its separate power source). When the relay is powered from the BCS, the relay works fine.

Also, if I ground the output from the BCS after turning the output off, the output will then turn off. If I don't ground it, the output still maintains the 7 volt output even when off.

[JonW]

The voltage has not been going on/off when I activate/deactivate the output (when the relay is powered from its separate power source). When the relay is powered from the BCS, the relay works fine.

Also, if I ground the output from the BCS after turning the output off, the output will then turn off. If I don't ground it, the output still maintains the 7 volt output even when off.

The standard BCS power supply is 6V and your outputs should be closer to 5V. Long term, I would not suggest using 9V input to the BCS for driving it as the voltage regulator will likely be running hot. However, I don't think that is the problem here.

The voltage measurement I was referring to was to measure with nothing connected to the BCS output. The results you're getting are a function of the way the relay board is designed. Even though it is set to trigger on the high (5V), it does not have a VREF input (voltage reference), so it's not signalling to turn off when the BCS is off because the BCS output is floating. That's also why it does work when powered from the BCS because it is using the same reference voltage. Unfortunately, you can't continue to power it that way because the combined coil's will overdrive the BCS power supply and voltage regulator.

Unfortunately, I think you need a new relay board. Many of the ones that say they works with Aurduino, AVR's, TTL, etc. should work. Many of us here have used ones from "Electronics Salon" on Ebay and they work well. Possibly we can get some posts of what other boards have been plug & play also.

[midway27]

I do not believe I explained my last post correctly. When I measure with nothing connected to the BCS and the BCS output on, I get a reading of 7 volts like expected. When I deactivate the output of the BCS, I still get a reading of 7 volts, instead of 0 volts. If I then ground out the output from the BCS to the control panel, the BCS output will "reset" back to 0 volts.

I'm not understanding the problem with my relay either. Both the BCS and my relay board are sharing the same ground. Is there a difference between ground and Vref in this situation?

[JonW]

Hard to tell here what's going on. Your outputs should be at 5V, not 7V, so that alone could have an affect on the port latching.

Yes, the VREF is different from the shared ground, although sometimes it is also connected to the shared ground (it can be connected to positive or negative depending on which is being used as the reference voltage).

I recently had a 4 port relay board that exhibited a similar issue. I was able to bypass the opto isolators and trigger the darlingtons on it with the BCS 5V outputs. It was a hack job, but it worked.

I'm sorry I can't give you a definitive answer as to what the problem is, but likely it is simply the relay board you are using and/or the voltage level you are running at. Is there any particular reason you're not using the supplied BCS 6V power supply?

[midway27]

Fixed! I connected the supplied 6 volt wall wort the same way as I was the 9v supply and sure enough it worked. Something must be wrong with the internal latching of the BCS when powering it with a 9v supply. Still doesn't explain why the relay would work when powered by the BCS though...

The relay also works fine now.



The technical specifications for the BCS are very misleading... At the bottom of the below link it states that an alternate transformer can be used if it meets/exceeds the below specifications:
Output Voltage 6Vdc Min / 10Vdc Max

My transformer was within these specifications and caused the BCS to function improperly.


http://wiki.embeddedcc.com/index.php/Te ... ifications

Thank you for all your help Jon!

[JonW]

Good to hear it's working!

I agree about the specs. I'll talk to Derrin at BH/ECC and see if that should be revised.

Did you measure your power supply DC output and verify it was at 9V?

[midway27]

I did. I was measuring right at 9+/- .1 volts.