Omni Pro II and external ATW Doberman Sounder problem

[torque]

Hi All,

I have hooked up an ATW Doberman Plus Sounder/Strobe to my Omni Pro II for my external sounder. I set it up so that the stobe stays latched after an alarm event.

It all works fine except for one problem....I can always here a very faint siren sound emminating from the sounder....all day....all night.

It is very faint, but I can hear it from the ground and the sounder is mounted 20 feet in the air. I've tried different resistors (1/2watt and 1/4watt) with no luck.

I am considering just purchasing a new sounder setup.

1. Is there something I can do to eliminate this annoying siren sound?

and/or

2. IS there a better sounder / latchable strobe combination that this community reccomends?

Thanks!

PS- This is the Doberman I have: http://www.mascon.com/atw/security-products/The_Watchdog_Collection/IndoorOutdoor_Siren__Strobe_Combination-The_Doberman_Plus/

 

[HAI_fjh]

I have used dobermans on a couple of jobs and the issue is that they are just too efficient. They make a lot of noise but draw very little current. Normally this would be a good thing, but the Omni always passes a small current through the sounder for tamper protection. If someone cuts the wire to the sounder the Omni can detect it.

Anyhow the solution is to add a resistor in parallel with the sounder to shunt some of the current. Usually I just use one of our 1K ohm resistors in parallel with the doberman. To preserve the tamper protection you should do this at the doberman end of the wire rather than the panel end.

I noticed that you said you already tried "different resistors (1/2watt and 1/4watt) with no luck". In the case of the resistors the wattage is not the important issue. Wattage is just a measure of how much heat they can dissipate. The resistance value is what is important. The resistance can be read by looking a the colored bands on the resistor. I am not going into how to read resistor color codes (Google it if interested) but I have always just used the 1K ohm 1/4 watt EOL resistors that come with the panel. If one does not work, put 2 in parallel, but 1 has done it for the doberman in the past.

One caveat: I have not used a doberman plus, only the doberman but I assume the actual sounder is very similar in both units.

Here is an excerpt from the KB article that discusses this:

Sounder Chirps or Sound when System is not in Alarm

What type of HAI Controller is it? Omni LT, Omni II, and Omni Pro II…

You will notice that in its normal state (Horn output off) that there is 12VDC between Int Horn and GND and between Ext Horn and GND. This is used for bell supervision. We send 12VDC through the horn wire to monitor for a short or an open, even if "SUPERVISE INT SNDR" and "SUPERVISE EXT SNDR" is turned off. There is very little current and hence should not cause any sounder to activate. If the device does activate, simply put a 1K resistor across the output (or device), preferably at the end of the line to maintain supervision. This will eliminate the problem.

 

[torque]

Okay thanks. I will look into getting some 1k resistors. The ones I was using (only at the panel side by the way) were 4.7k purchased from Radio Shack.

I think I still have the 1k resistors that came with the panel. Do they look like this? http://www.hobby-hour.com/electronics/resistors/1k-resistor.gif

 

[HAI_fjh]

Yes.
Brown = 1 (first digit)
Black = 0 (second digit)
Res = 2 (number of zeros)
Silver = +/- 10% (tolerance)
So that is 1000 ohms (1K ohms) +/- 10%
This should be fine.

 

[torque]

Okay thanks. I will climb up the side of the house and try to install one. This is what the instructions on the Doberman say for wiring:

Red-positive (strobe & siren);
Brown-positive (strobe only);
Black-common

I assume I will be putting the resistor only on the Red?

 

[HAI_fjh]

The resistor should go between the red and black wires.

 

[torque]

That did it!! Thanks!