Beacon keeps flashing...

[ms2004]

Looking for some advice. Have a Klargester treatment plant that has a control panel monitoring its functions/faults. When a fault is detected, the system flashes a beacon outside. For the past 6 months or so, the beacon has been flashing, but there is no fault. The beacon doesnt flash as it would with a genuine fault. It flashes a dim light, gets brighter then more dim again.

When i took the beacon apart, there is a small printed circuit board with a wire to the bulb. There was moisture inside so I dried it out and re-connected it. This has not fixed the problem. A new beacon is £99 so I want to be sure its the beacon and not another fault with the control panel. The beacon is connected to 3 terminals inside the control panel, L/N/E. I assume current is sent to the beacon in the event of a fault but I'm not sure.

Is there anyway to test this using a multimeter? I assume that when no fault is present, no current should be sent to the beacon but I dont really know. Any advice would be appreciated. Im reluctant to buy another beacon without being 99% sure thats the problem.

Thanks in advance.

 

[crystal ball]

What is the operating voltage of the beacon?

 

[bernardgreen]

I assume that when no fault is present, no current should be sent to the beacon .

That is a safe assumption (*). Normally the beacon would be switched on by a relay contact that closes when the system has fault.

Dim and/or erratic flashing can be due to a small amout of current reaching the beacon due to leakage through damp across the relay contacts or capacitive coupling of current.

(*) Almost certainly not applicable to your system but a fully fail safe indicator would have a battery in the beacon which powers the beacon when a "hold off" voltage coming from the controller is removed. This ensures the fault of "total power failure" will light the beacon for as long as the battery lasts. Moisture or component failure in the beacon could cause dim light and/or erratic flashing.

 

[ms2004]

Thanks for the replies. There is no battery in the beacon unit and as there was moisture present, I assumed the beacon is faulty rather than the control panel. I will buy another beacon.

 

[baldykev]

If the beacon if on, then it must be getting a feed from the control panel.

 

[SimonH2]

Do you have schematics for the panel ? Not really needed for this issue, but generally useful for troubleshooting. If it's a custom panel thdn I'd expect schematics; off the shelf package, generally not.
As above, if there were no power being supplied to the beacon then it could flash as described - so that suggests a panel fault rather than the beacon.
This is whete the schematics come in. As above, it is likely, but not guaranteed, that the beacon is switched by a relay. So it.might need the relay to be faulty - had a bit of damp and some "tracking" as a result. Or there might be a snubber across the relay contacts which has (partially) failed. Or the circuit is switched by a semiconductor (perhaps internal to a small PLC) and there's a slight leakage through it - damp again ?
I would be tempted to try a small light bulb in place of ghe strobe - something of a similar power rating so as not to risk overloading whatever is switching it. See what voltage you get across it with no faults - this would be a useful test with the "faulty" beacon as well.
One possible fault could be a combination of supply leakage together with a "dummy load" resistor having failed in tne beacon. Normally the dummy load would dump the leakage - but with it failed, the leakage can partially charge the electronics in the beacon and it does "odd things".