Re: Alarm panel won't drive bell current

[Jim <alarminex@xxxxxxx>]

Change the batteries.=20
The batteries share the load of powering the bell/siren when the panel is i=
n the alarm condition. A dead battery has low resistance therefore the pane=
l transformer is trying to provide current for the panel, the keypads the m=
otion detectors the smoke detectors the almost shorted bad batteries and th=
e bell/siren. Batteries are to be changed every three to four years NOT nin=
e years. Likely your bell/siren hasn't been able to ring for a number of ye=
ars because you ignored the low battery signal.=20

Apparently, one of the other short comings of DMP panels is that it lets yo=
u ignore a failure of a vital supporting function. Other panels give you a =
constant warning until the batteries have been changed.=20



On Sunday, March 9, 2014 3:20:22 PM UTC-4, blueman wrote:
> I have a DMP XR200 alarm panel with the bell output driving an MPI-11
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> siren driver. The panel bell output supplies 12VDC @1.5A max via an
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> output relay.
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> When the siren driver is connected, I can hear the bell output relay
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> switch on but then within about 1/2 second the relay immediately switches
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> off -- this occurs in both pulsed and steady alarm modes.
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> The siren driver itself seeems to be working and the panel itself seems
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> to have sufficient amperage, because when I connect its inputs directly
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> to +12VDC on the panel, it properly drives the alarm speakers at full
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> volume, drawing only about 0.4Amps. My oscilloscope confirms that the
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> output is the expected pseudo-sine wave.
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> This led me to think that the problem must be with the panel bell output
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> circuitry.  However, when I disconnect the siren driver, the relay stays
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> on and the voltage to the bell outupt is ~12VDC as it should be. I then
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> tested it under load using a 10ohm 10W resistor and even under load, the
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> relay still stayed closed -- using my DVM I verified that the panel was
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> sourcing ~1.2A without tripping the overcurrent protection. So, at least
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> with a static load, all seems to work fine on the panel.
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> I then noticed that the siren driver has a 2200 uF cap across its
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> input. When I put a similar 2200uF cap across the panel bell output, it
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> caused the relay to switch off. Similarly, when I temporarily removed
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> the 2200uF cap from the siren driver, the siren driver board no longer
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> caused the relay to shut off. (I also tried swapping a new 2200uF on the
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> siren driver and it still caused the relay to shut off)
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> So I can only conclude that the transient current draw used to charge
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> the 2200uF input capacitor is somehow tripping some internal overcurrent
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> protection circuitry on the XR200 panel. Note that tripping only causes
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> the alarm output to stop -- the rest of the panel functioning is
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> unchanged.
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> Until now, my alarm has been working reliably for the past ~10
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> years. So, it seems like something has gone wrong in the current
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> oversensing circuitry for the bell output.
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> Has anybody experienced similar issues before? Any thoughts on how to
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> further troubleshoot & fix?
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> One other aside which may or may not be related. The alarm a few days
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> ago started showing a battery trouble which by itself didn't seem
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> worrisome since the batteries are about 9 years old. Meanwhile, I have
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> new batteries on order.
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> But this still leaves me to wonder whether the two problems may somehow
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> be related. Did the battery issue trigger the bell output issue or
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> vice-versa? Are the batteries even bad or is the 'trouble' really just
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> triggered by something wrong with the board. (Note: I only discovered
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> the issue with the bell output after I noticed the battery trouble but
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> it may have preceded that too)
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> (note: disconnecting the batteries did not stop the problem with the
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> siren driver -- I thought initially perhaps that bad batteries could be
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> drawing too much current but removing them had no effect).