Door Sensors

[KentDub]

I'm in the market for some door sensors.

I want them hardwired, supervised and recessed. I will be hooking these up to my Elk M1G. There seems to be almost too many to choose from, magnetic, button, etc.

What door sensors are your favorites (manufaturer and model please) and why? Also, what part of the door frame do you mount these things to?

Thanks for helping a noob,
Kent

 

[pete_c]

I currently utilize recessed magnetic. Some are installed above the door, side of door and bottom of door frame.

 

[AceCannon]

If yo use the door sensors that have a depress-able "ball" in the middle (they go on the hinge side of the frame), make sure you install blanks and only install the actual sensor AFTER the frame has been painted. The paint will totally muck up the works and the switch will very likely have to be replaced.

(yes, I know from experience. one frame has to be repainted, and the sensors got fouled up)

 

[42etus]

I like these http://www.smarthomeusa.com/ShopByManufact.../Item/951WG-WH/ . Installed in the top of the door frame.

 

[Neurorad]

The plunger contacts should be installed on the hinge side of the door only.

Good tip on the paint - don't let anyone paint your plungers.

 

[KentDub]

Thanks for the tips.

This is all retrofit and everything is already painted. I've already done so much drywall damage to the house that I'm just going all-out to wire everything so I only need to have the drywall dude come out here once to fix everything.

I'm a little confused on some of the specs for the magnetic sensors. What exactly is gap size? It sounds like the maximum distance the magnet can be from the sensor. Products seem to imply that the larger the gap size the better. Wouldn't a large gap size be bad (as in, allow a door to be ajar but not closed but it still registers as closed)?

Also, are there specific versions of sensors I need to buy if I want to make them supervised? It seems to me that if you pigtale the EOL resistor all someone needs to do is rip the sensor out from the door frame and it wouldn't cause an alarm.

Thanks!
Kent

 

[pete_c]

My doors sound if left ajar. I soldered my EOL resistors and used heat shrink tubing. A bit time consuming. Once the sensor is put into place its difficult to remove it without some efforts. I used the 3/8" magnetic sensors that Worthington sells. The sensor is around 3/8 in diameter with teeth on it so I tapped them in place with a piece of wood and a hammer. You don't even notice them. Once painted you noticed them even less. If you have bottom door thresolds you can even install them underneath the thresold. In FL had the house prewired. All the exterior door have the sensors on the top of the door frame. All of the sliding glass doors have the sensors wired near the locking clasp. I was concerned a bit drilling into the frames of the sliding glass doors but after doing a few had no issues. (6).

 

[Neurorad]

Some of my plunger contacts have failed after 15 years - I guess it's prob dirt getting into them, as they haven't been painted.

 

[KentDub]

I soldered my EOL resistors and used heat shrink tubing. A bit time consuming.

Do you have a picture of this by chance? I'm still trying to figure out how to make it supervised. I ordered some magnetic sensors and got the terminal type instead of the 12" leads.

Thanks,
Kent

 

[Quixote_1]

I soldered my EOL resistors and used heat shrink tubing. A bit time consuming.

Do you have a picture of this by chance? I'm still trying to figure out how to make it supervised. I ordered some magnetic sensors and got the terminal type instead of the 12" leads.

Thanks,
Kent

My understanding is that you just wire the EOL in series with the reed switch (door sensor). The Elk watches the zone for it's resistance once you set it up for that. Just wire it in right after the sensor in a discreet way so that if someone manages to get at the wire somewhere down the line and short it so that they can defeat the sensor, the Elk no longer reads the same resistance on the wire and sets off the alarm.

 

[Desert_AIP]

I soldered my EOL resistors and used heat shrink tubing. A bit time consuming.

Do you have a picture of this by chance? I'm still trying to figure out how to make it supervised. I ordered some magnetic sensors and got the terminal type instead of the 12" leads.

Thanks,
Kent

I soldered the ends of the resistor to some 22 ga wire then covered the whole thing in heat shrink.
When I installed them, I just had to use B connectors to hook up the EOL resistors to the zone in series.

 

[KentDub]

I understand that cutting the wire downstream from the sensor will trigger an alarm because the Elk will be able to monitor the resistance change. What I'm concerned about is if someone where to gain access to the sensor directly they would be able to remove the sensor after the EOL resistor so the Elk wouldn't detect the tampering. When the sensor is pigtaled it seems to allow you to have a small area where you can cut the wire. I guess there is some truth to TV shows where the people are always trying to figure out which wire to cut? Isn't there a way to wire up a sensor where it eliminates the small area of wire you can cut?

 

[WayneW]

I understand that cutting the wire downstream from the sensor will trigger an alarm because the Elk will be able to monitor the resistance change. What I'm concerned about is if someone where to gain access to the sensor directly they would be able to remove the sensor after the EOL resistor so the Elk wouldn't detect the tampering. When the sensor is pigtaled it seems to allow you to have a small area where you can cut the wire. I guess there is some truth to TV shows where the people are always trying to figure out which wire to cut? Isn't there a way to wire up a sensor where it eliminates the small area of wire you can cut?

CUTTING into an EOL circuit ANYPLACE will violate the zone, regardless of EOL placement. EOL circuits are essentially normally-closed loops, so any opening is a violation. The tamper risk is if someone were to access a sensor and BYPASS it with a jumper wire, effectively shorting out that sensor so the circuit stays constant, regardless of switch position. Therefore sensor wiring & connections should be hidden. Sensors with a built in EOL are not able to be bypassed with a simple jumper wire (you must use a proper resistor as a jumper at the EXACT instant the switch is violated), but you can only use one of these EOL sensors per zone.

 

[Photon]

I decided I don't need whatever extra bit of protection is provided by EOL resistors. In exchange I have fewer points of failure and better noise imunity. Since all my wiring to mag contacts is burried in the walls, I don't feel I'm compromising security. The best sensors I have on exterior doors are actually in the strike box for the deadbolts. No chance I'll see a "system ready" indication if a door is slightly ajar. I used Elk rules to let me know if someone sticks a magnet in the box while it is disarmed to trick the system. If the door is open but the deadbolt is secure, then something is amiss.

 

[ano]

The real reason for EOL resisters is not because of a skilled thief. Its that the EOL resistors assure that the wiring is good. You'd be surprised over time how many wires get pinched or melted together. Without a EOL resistor AT THE SENSOR you would never know this. They are there for a reason, so just use them like they were intended.

As for sensors, magnetic ones use glass sealed reed switches which are VERY reliable when used correctly. You want the magnet to move toward and away from the sensor, NOT slide across. The sliding can magnetize the sensor over time. I'd stay away from plungers for alarm sensors. They get lots of dirt in them and don't last very long. Magnet sensors installed correctly are your best bet.