So I decided to go ahead and use one of the xACs I had to trigger my garage door. I initially bought 3, one for each of my bikes, but after doing the first one I decided to see what other projects I could use them for. I ended up having to replace the one on the bike after I rode in a storm and the waterproof compartment wasn’t so waterproof, so that leaves me with 1 left.
Yesterday I tried installing it but the relay wouldn’t trigger. I thought perhaps the DPDT I used was a bit large and the trigger current might have been too much so I ordered a pack of basic 12V SPDT marketed for auto use.
Well, these aren’t triggering either. I’ve tried two different power supplies, and both will trigger the relay no problem by themselves, but when I wire up the xAC it’s no good. I get the red LED on and measurements at the trigger wire show 7.3V when attached to a load (the relay), but 12V when left off. Do I just have a dud or…? Any help would be appreciated.
Wiring:
PS 12V -------> xAC red
PS GND --------> relay pin 85 and xAC black
xAC white ---------> relay pin 86
Did you use a diode between relay and xAC?
When the power turns off, the magnetic field collapses and can “kick back” at the xAC. Can hurt it.
If No, then add one.
If Yes, then turn it around and see if that works.
What kind of power supply? It seems awfully odd that it drops to 7.3V
Also, recheck for solid connections. It’s bit me more than once.
I’ve tried 3 power supplies now, just got done testing a larger 12V 5A unit. The other two were 12V 1A and 12V .5A. My Fluke shows correct voltage out of all three.
The 1A PS has a voltage selector on it and on a whim I set it to 9V and recorded ~5V at the trigger when connected to the relay. That’s the same roughly 40% voltage drop as at 12V.
If I can’t figure it out I may just pick up a 5V relay.
Are you able to use your meter to confirm there is 12v out on white wire while authorized tag is present? Disconnect from the relay and just test the output wire. Also, what is the red LED on the xAC doing?
ok… so now connect the diode and test on the other side of it… if you are not getting 12v on the other side of the diode, then either 1) your diode is backward, or 2) your diode is trash and needs replacing.
12V. The 9V was just a test I did from a variable PS I had.
I tried three different power supplies, 500mA, 1.0A, and the last and still connected, 5A.
Yeah, 12V strong being supplied
Exactly, I’ve tried two different relays to make sure, a DPDT and SPDT and neither worked. I’ve got a 5V on the way today that it looks like I’ll end up using.
I just pulled the diode and it recorded 7.6V at the terminal, which was just enough to trigger the relay. However that’s not enough wiggle room for me so I’ll just wait for the 5V relays to come and also go looking through some of my spare power supplies to see if I’ve got something 12-15V to test, too.
So this xAC is for your Motorbike?
Your battery will be Nominal of 12v but I would expect it would be around 12.7V
and maybe upto 13.7-14.7V when the engine running.
If you wanted to do one more test on a vehicle battery rather than Power Supply, that might answer your question…
Little bit of history, these were originally automotive immobilisers. Surplus stock got reworked into the product we know and use. That’s another way of saying somebody took a soldering iron and made a few changes.
On the picture below, you should be able to follow the yellow line from the LED wires to the White wire. It should be 12V, except near the LED after it passes through the tiny little resistor. The trace passes through the board from one side to the other at Point A, and Point B.
I bet if you check the voltage (while under load from relay) at some point along that trace, that you’ll find it’s 12V like it ought to be.
My guess is that the modification circled in green didn’t get a good solder connection and is causing unnecessary resistance. That’s why it’s only checking low under a load.
There’s a tiny voltage regulator to the left of the green circle. It’s been resoldered. Check that, and really that’s the last thing I can think of. It may not be worth further effort.
My only other suggestion would be a super up close inspection of the whole thing looking for cold solder joints or other odd stuff.