IVB\’s Home Theater and Home Automation

You don\’t have to spend a lot for that smarthome.

Fantastic advice from BSR at Cocoontech.com

Posted by IVB on May 16, 2006

I got some FABULOUS advice about babystepping through an Elk setup from brave sir robbin over at cocoontech. Thought I'd share with everyone. To see this info directly and all the back&forth, see http://www.cocoontech.com/index.php?showtopic=4346&st=30 


BraveSirRobbin, a Cocoontehc.com moderator, said:



You can learn a lot by taking it step by step and using a multimeter.

For instance, I asked the question earlier if the smoke detector opened or closed its contacts when smoke was present (alarm condition). You can easily test this as follows:

I don't know how familiar you are using a multimeter so I will go over the very basics. Place your multimeter in "ohms" mode (horseshoe shaped symbol). Now short the leads of the meter together. You should see a near zero reading (probably something like 0.01). Now separate the leads. You should see something like "OL" which shows an open circuit or "infinite" resistance.

Now, just for grins set an Elk EOL resistor on a table and touch each end of the resistor with the meter's leads. When measuring resistance you HAVE to make sure your fingers are not in contact with the item measured as your body resistance could have an effect on the resistance being measured.

You should see something like 2180 which is within the tolerance of the 2200 ohm value.

A must have along with your multimeter are a good set of Clip Leads for your meter. This will let you clamp on resistors and give you hands free operation.

Also a set of THESE clip leads are good to have for configuring test setups on a bench.

Anyway what you can then do is remove the signal leads of the smoke detector from the Elk zone input and connect those leads to your multimeter and keep your multimeter on ohms measurement. You should be reading the value of the EOL resistor (assuming you properly have the EOL installed near the smoke detector). This is why you should get around seven volts when the smoke detector is connected to the Elk and is in the normal state as the resistance between the plus and ground of the zone is reading this same 2200 ohm resistance.

Now place the smoke detector in an alarm condition. Did the resistance reading go to near zero or infinite (open circuit)? It has to do one of the two. If it went to open circuit this means that when the smoke detector is in an alarm condition and hooked to the Elk it will see around 13.5 volts. If the resistance went to zero the voltage in an alarm condition that the Elk would see would be zero volts.

Does this make sense? By using a multimeter on a "contact closure" sensor (motion, smoke, glass break, magnetic contact, etc…) you can figure out what resistance you are giving a zone in the Elk on a motion/no motion, glass break, no glass break, open contact, closed contact, etc… condition with your sensor. Please note of course that if your sensor requires 12 volt power you have to have that connected for any of these tests to work.

OK, now that you know what resistances you are giving your Elk on both of the smoke detectors conditions you really don't need to have that smoke detector connected while testing your Elk zone inputs do you?? You can just use an EOL resistor and SIMULATE those conditions. This is the testing I was describing with the EOL resistor above.

Does this make any sense? You can see how you separate components and test their performance individually first before hooking them up?

Actually since I'm hard core on testing, I would have first rang out the cables going between the Elk and all my sensors before I installed anything. I'm sure you read the How To Install A Security System How-To and performed this testing on your cables before you started wiring your system! wink.gif

Cable problems will lead to nightmare troubleshooting issues. I had my home pre-wired for security and I had shorted wires as well as open runs. Luckily I checked the wiring before I started connecting anything. Using the clip leads and a multimeter you can very quickly check your wiring and it is probably worth doing so, especially if you had a (and I use this word loosely after seeing the results of my new home) "professional" installation (i.e. did not do it yourself). Most installers will not take anywhere NEAR the care you will do and will yank, pull, tug, staple, and almost multilate wiring just to get it in place, especially if they are not around nor responsible for the following install!

Oh one other thing. If you are seeing zero ohms in your test with the smoke detector during a "smoke" or alarm condition and want to simulate this while testing your zone expanders I would just place an EOL resistor between the zone inputs of the Elk and then "short" (place a clip lead on either end of the resistor) across the resistor to simulate "smoke".

This way you will not have to disconnect the EOL to place a shorting wire across the zones like I first suggested. The reason is you will first have introduced an "open circuit" while taking your EOL out and putting a shorting wire in. This way you can just go from EOL to short without introducing an open circuit between those steps.


BraveSirRobbin (BSR)
CocoonTech Moderator


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: