Addressable Problem any ideas?

[Wiz]

The only way to see if capacitance is affecting the data is to use an oscilloscope to see how it is affecting the waveform of the data pulses. There may be ways of compensating for the effects of capacitance, but I would suggest that you talk with Techincial at Apollo for advice because modifying capcitance values is fraught with potential problems.

Putting a resistor across a pair of wires carrying data is generally used to increase the current flow in the circuit. When more current is flowing in a circuit, the affect of low-current but high-voltage external interference is reduced. I'm not sure that this will help in this case because the problem seems to happen when higher currents are flowing anyway (i.e. the sounders are operating)

[David Rooney]

Do you have the same problem if you stick 0 volts on the "continuous" input ?  not sure what you mean by this David.

If you put 0 volts on the CNT terminal - remote input - it forces the panel to send a global "turn on" command to all sounders pretty much instantaneously - used for class change.

It would prove that there is definately no cause and effect issues that could be affecting the sounders... which I guess are all set to default ring ?

[spanner]

I know this sounds silly, but when you press the silence alarms button, do you press it ONCE it and wait for all sounders to stop, or do you press it more than once as the sounders have not stopped instantly?

Reason I ask is the silence button is also a resound button, if you press it once it will send a “silence” signal around the loop, (which on some panels like Kentec and Ctec can take a while to fully circle the loop) if you press it again you will send the “resound” signal around the loop. Which sounds like your problem.

I use to get this as a common call out with some panels as the customer would press silence and expect the system to silence instantly, and because it does not, they get impatient, press it again which re sounds the system. (if you press silence/resound too many times on a cretin closed protocol panel they have a tendency to go into CPU fault and lock up with the sounders active and no way to silence) )

[bibbage]

Hi Spanner.
I realised this could be the problem so I tried it again and made sure I only pressed silence once, but I had to press reset at least 3 times before the sounders stopped completely.  Of course there is also the problem that OMT doesn't work either, it all works fine with the sounders disabled though!

[David Rooney]

Putting a resistor across a pair of wires carrying data is generally used to increase the current flow in the circuit. When more current is flowing in a circuit, the affect of low-current but high-voltage external interference is reduced. I'm not sure that this will help in this case because the problem seems to happen when higher currents are flowing anyway (i.e. the sounders are operating)

Surely if the voltage is fixed ie. 24volts then increasing the resistance across the circuit must decrease the current ?

[Wiz]

David, if you add any resistor in parallel with an existing circuit the overall resistance of the circuit is always reduced and, Ohms law shows us that, therefore the current drawn by the circuit increases.

In systems carrying data using voltage pulses, the liklihood of it being interfered with by RF and EMI created by nearby electrical systems is reduced by more current being drawn in the circuit. Increasing the current decreases the liklihood of interference.

This is why you will find that many systems using data being transmitted over a pair of wires require a resistor to be connected and the end of the circuit as standard. I have noted that this is often a 120R resistor. Such a circuit running at 12V DC therefore has 100mA flowing through it due to the resistor plus whatever current is drawn by the actual equipment on the circuit.

There are a lot of other parameters to take into account when loading a data signalling circuit with a resistor, but it is generally something well worth trying when that circuit is being affected by corruption.

[David Rooney]

Top man... never knew that.

Thanks Wiz.

[firefly41]

 A bit late- I know- appologies had a very similar problem on kentec solo (10 years ago) with a mixture of loop imterfaces and conventional sounders. When testing silently all worked perfectly with the bell circuit connected loads of weird stuff happened lights not coming on detectors, interfaces firing willy nilly etc etc. the bell circuit wire was causing the problem only one wire had to be connected for problem to happen. Never found out properly what it was but assumed it was the proximity of the wires in conduit( Fp100 in galv conduit) (And the sudden change to +V when sounders operate) stuck a relay on sounders with thru monitoring but powered from separate psu sorted problem. Have not heard of anything like it recently assumed been fixed by manuf