Protecting M1 from External / Outside devices with fuses

[Jozza]

Hi All,
 
I'm trying to find out whether there are any risks associated with external PIRs or other devices being used as a way of compromising a security panel - in my case a Ness/Elk M1.
 
Scenario would be that someone compromises the cabling of an external PIR, and applies a large electrical charge through the cable to the panel. Is this a concern? And if so, what are the approaches to address this?
 
Jozza

 

[Del91574]

Transorbs or surges with a clamping voltage slightly above the zone voltage....say 14VDC. The easiest ones to source would be those designed for a fire alarm SLC or similar.
 
The higher voltages would clamp to ground until the transorb is damaged and bridged to ground or burns out.

 

[ano]

Chances are anyone that is smart enough to do that wouldn't be breaking into your house so that they can sell your stuff on eBay to buy more crack.

 

[Jozza]

OK, so based on Dell's input I've done a bit of hunting around. It appears these devices are technically known as TVS (Transient Voltage Suppression) diodes, and I was able to find some specs from Littlefuse for a range that appear on appropriate.
 
Dell - any chance you can have a look at the spec sheet here http://www.littelfuse.com/data/en/data_sheets/p6ke_revised.pdf and suggest which model would be appropriate? I'm thinking that it would be either the P6KE12A or the P6KE13A for 12V PIRs and Motions external to the house.
 
Never knew these things existed.
 
Jozza

 

[dgage]

Damn.  That is good to know.  I'd want some of those to protect some of these fancy new irrigation controllers.  Del, can you suggest one for that as well?  Thanks.

 

[Del91574]

No silver bullet here. Usually I'm lazy and get what I need via the trade route (why reinvent the wheel here) and just choose a clamping voltage just above the normal operating voltage(s). All the engineering and hard work is done (per se) by someone else and the unit comes in a slick box with connections for the cabling and then a EG connection.
 
Been too long of a week to dig through more documents at this point...sorry.

 

[Jozza]

No worries, thanks anyway Del. They're not too expensive so I'll order a few and give it a go.
 
Given that each PIR has 8 core cabling and I'm looking to mitigate risk of malicious tampering, I'm assuming I'd need one per cable core? Anyway, might experiment in a couple of months time when I start the fitout and post back my results.
 
Jozza

 

[jpmargis]

I'm looking forward to the post where you say, "Whoops, my protection circuit didn't work quite the way I thought it would and now my ELK M1G has stopped working.  What can I do to get it working again?"

 

[gatchel]

The last time I checked, adding any form of surge protection to anything was never a bad thing. Process of elimination and some basic troubleshooting skills can determine if a surge device has gone bad.
 
Ditek makes some decent units for just about any voltage and combination of conductors in a security environment.

 

[Del91574]

Surge protection is pretty easy to install and troubleshoot....it's done almost all the time.
 
Moving into a brew your own with components, you may have some small growing pains, but it's not rocket science and we're not talking about a complex access panel or PLC....generic voltage output and  zone inputs.