Elk Zone Input Expander Problem


Active Member
My current configuration has three (3) Input Expanders.

Problem: Suddenly the Input Expander #2 loses communication with the panel and it causes alarm to all of the zones connected to Expander #2.

1. I went into ElkRP and attempted to re-enroll the module without success.
2. I then power down/up the system and re-enroll the module and it works fine now.

My question is why does it happened? FYI, it happened once before (about 2 months ago) and at the time I didn't give it the attention that I should.

Please help
I'm very sure the terminations are correct because I have the panel and these 3 input expanders installed and working since October 2005. Like I stated before it happened once about 2 months ago and it happened again last night while the system was armed.
I have the same or similar situation with a keypad. I was on vacation and came back and it lost communication. The wiring is fine. Still havent figured it out but havent had time to dig into it.
Make sure the data bus has proper termination. Power down the system and measure the resistance between data A and data B. It should be about 65 ohms.
Also make sure that all modules outside the metal enclosure is wired in a series configuration with terminating resistors at the extreme ends of the data bus.

Look at the data bus errors on the keypad user menu 8,6,1. You should not see the errors incrementing. Over a long time you may see some accumulated errors.

If powering down the board and repowering it made it start working, it sounds like a silicon latch up on the microprocessor from a transient. The hardware watchdog should have automatically powered down and backup the input expander's power supply, breaking any silicon latchups. There is a WDD or watchdog disable jumper on the input expander. Make sure it does not have a jumper installed on it. Another possibility is the watchdog circuit has a circuit problem and unable to power down the power supply should the micro be forced out of program from a transient.

If you loose an input expander with burglar zones defined on it and the system is armed, the M1 assumes a burglar cut the data bus and the zones go into alarm.

Bozon Flux Discharge????? ;)
I just did a little troubleshooting and it looks like my keypad took a hit. It displays lost communication and I try cycling the power and does not correct the problem. I swapped the keypad with the one from the kitchen and it works fine in the bedroom so the wiring is fine.

I bet when I was on vacation we had a lightning storm and the bedroom keypad got a piece of it.

My cable modem is also flakey since then as well.

Oh well at least it wasnt as bad as Electrons.

I turn off the power to the M1 and measure the reading across terminals A and B of all three (3) input expanders and the Data Hub and they all read 73 ohms. Is it within the tolerance?

I also noticed menu 8,6,1 the error reading accumulate to 153 for (A2T4) after about a week since the sytem was power down. Is it normal?