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vulnerability? Power short causes system hang
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 Posted: Monday Sep 29th, 2014 01:55 pm
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richylloyd
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I have a number of long range, external PIR's that handle external lighting and 'arriving home' scenarios.

When installing the PIRs, I inadvertently shorted the power supply which froze up the main Comfort board.  I needed to remove all power to the board to get it functional again.

My concern is that some of the PIRs are readily accessible and do not have any tamper mechanisms meaning that the system is potentially vulnerable.

Can someone please help me undrestand how Comfort should be responding to a power short? 
Will it be different if the system is armed or not? 

My workaround is to drive these PIR's off a separate 12V power supply but this doesn't lessen my concerns for the system vulnerability.



 Posted: Monday Sep 29th, 2014 05:55 pm
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slychiu
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A short on the 12V supply should cause the resettable fuse to open so the external 12V to the PIR should be lost but the controller should still have power

Does your system have a 12V backup battery?



 Posted: Monday Sep 29th, 2014 06:10 pm
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richylloyd
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Thanks for the response.

yes, I have a backup battery.

I had to remove the main fuse as well as the battery lead to reset the system.
If there is a time delay for the resettable fuse to kick back in, I haven't found what it is (took 5 mins from removing the short to finding the method for resetting the syem).

What is the expected impact to the keypads as that is really where I saw the issue play out?
Could it be that the main board was actually running and just waiting to return to a normal state?
I will test this again today to ensure it is not just a misunderstanding of the system reaction.



 Posted: Wednesday Oct 1st, 2014 09:34 am
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slychiu
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A short circuit on 12V should cause the resettable fuse to open within a few seconds, provided a backup batery is connected. When the resettable fuse opens the 12V will not be available to keypads or other devices
The rest of the alarm will still operate

You do not need to remove the batery and fuse to reset the system
There is a reset button on the Comfort PCB
You can also send the reset command from Comfigurator



 Posted: Thursday Oct 2nd, 2014 02:00 am
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richylloyd
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Many thanks for your help
I haven't managed to reproduce the problem since and shorting the power supplies has not reproduced my previous experience.
With the knowledge of how the system should behave, I will just await a repeat event and test appropriately.



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