Re: Alarm panel won't drive bell current

[davek13815@xxxxxxxxx]

On Monday, March 10, 2014 1:14:19 PM UTC-5, Jim wrote:
> Change the batteries.=20
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> The batteries share the load of powering the bell/siren when the panel is=
 in the alarm condition. A dead battery has low resistance therefore the pa=
nel transformer is trying to provide current for the panel, the keypads the=
 motion detectors the smoke detectors the almost shorted bad batteries and =
the bell/siren. Batteries are to be changed every three to four years NOT n=
ine years. Likely your bell/siren hasn't been able to ring for a number of =
years because you ignored the low battery signal.=20
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> Apparently, one of the other short comings of DMP panels is that it lets =
you ignore a failure of a vital supporting function. Other panels give you =
a constant warning until the batteries have been changed.=20
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> On Sunday, March 9, 2014 3:20:22 PM UTC-4, blueman wrote:
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> > 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 switch=
es
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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 outpu=
t
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> > circuitry.  However, when I disconnect the siren driver, the relay stay=
s
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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, th=
e
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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 leas=
t
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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 th=
e
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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 overcurren=
t
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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).