Relay wiring

**cgalpin** · 06-18-2009, 12:16 PM

I can't believe I'm asking this but I am unable to get my relays working

This is pretty simple stuff so I hope it's not me doing something stupid, but it's likely I am

The relays (purchased with my FB) have 3 spade connectors

COM (common)
NO (normally open)
NC (normally closed)

My understanding and expectation is that if I have a working circuit (lets say a light bulb) and I take the wire providing 12v and put the relay in series, I can turn it on and off. Like I said, simple stuff (baby steps).

So I connected one end to COM and the other to NO. When I trigger the output port on the FB, the led lights, the relay buzzes, but my bulb never turns one. I have verified there is no voltage with a multi-meter. The NC side is always hot. I have tried 3 relays and don't expect this to be a hardware issue as they all behave the same way.

What am I doing wrong? Is it that the relay isn't really engaging? I have looked at the FB4 manual and tried all 4 possible jumper combinations for P13 if keeping the jumpers in the same orientation as shipped and there is no difference (I have 12v to P1).

Thanks,
charles

**Tidder** · 06-18-2009, 12:28 PM

The relay shouldn't buzz, it should just click... sounds like either bad relay, or not enough juice to the coil side of the relay.

**2k1Toaster** · 06-18-2009, 12:29 PM

you do have it grounded too right? Just making sure...

Also what power source are you using to power the FB?

**cgalpin** · 06-18-2009, 12:41 PM

I am just bench testing right now.

I'm using a power supply from an old hub/switch that puts out 12V DC (800mA). I assumed this provides ground as well. I'll try hooking it up to a car battery.

thanks,
charles

**2k1Toaster** · 06-18-2009, 12:59 PM

Originally Posted by cgalpin

I am just bench testing right now.

I'm using a power supply from an old hub/switch that puts out 12V DC (800mA). I assumed this provides ground as well. I'll try hooking it up to a car battery.

thanks,
charles

No I meant on the relay side. Nothing would work if the wall wart wasn't grounded!

Basically without the relay, does the light work? It should always be on. Then cut one of the wires and put the relay between it.

**cgalpin** · 06-18-2009, 01:01 PM

Yes the circuit works fine before I introduce the relay, LOL. I do feel pretty stupid right now, but honestly I'm not THAT stupid

No difference powering the FB from a car battery - relay whines. What's the max voltage I can apply to the relay trigger pins to test it directly (without the FB)?

**2k1Toaster** · 06-18-2009, 01:05 PM

Originally Posted by cgalpin

Yes the circuit works fine before I introduce the relay, LOL. I do feel pretty stupid right now, but honestly I'm not THAT stupid

No difference powering the FB from a car battery - relay whines. What's the max voltage I can apply to the relay trigger pins to test it directly (without the FB)?

The 12v wall wart you are powering it from should be enough to trigger the relay by itself.

**digital79** · 06-18-2009, 01:34 PM

Originally Posted by cgalpin

I take the wire providing 12v and put the relay in series

You connect the relay coils in series? If that's the case, each coils is getting way less than 12VDC (voltage/#of relays), so coil does not make enough magnetic field for the relay contact to move.

Did you test each relay individually?

**cgalpin** · 06-18-2009, 01:42 PM

No probably bad choice of words on my part. By series I meant I introduced the relay into the starting circuit by "cutting" one of the lines.

Testing with a single relay.

My circuit is simply this

12v -- bulb -- ground WORKS!

12v -- COM -- [ relay ] -- NO -- bulb -- ground BULB NEVER COMES ON

12v -- COM -- [ relay ] -- NC -- bulb -- ground BULB NEVER GOES OFF

I have bypassed the FB and still have the same behaviour though when applying 12v to the trigger pins. Totally stumped....

The only difference I noticed with the FB is I hear a hum when the relay is turned on. With direct 12v I hear a very soft click (but have to put my ear close to it to hear it)