Door Window Sensor, I don’t know how ADT sense open or closed?

Thread Starter

killivolt

Joined Jan 10, 2010
805
I work for a company that uses a sensor wireless com at 345MHz signal to report back to the PLC Panel, Camera’s, Door Locks, Garage Door Controllers are Z-Wave around 908.2MHz and are POE.

They use a Battery CR2032 3vdc and they continually go out, we have a Takeover device that takes the wired sensors like ADT uses and transfers those connections to a module that will send a wireless com to our panel.

1. I need to know if there is a chip that will DC to DC convert I high voltage such as used on a solar battery, down to 3vdc for the sensor.

2. I need to know how ADT reports open or closed, is it wireless also or TTL design? Like Hall effect which would make sense.


Thanks in Advance,

kv
 
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Thread Starter

killivolt

Joined Jan 10, 2010
805
Most use a reed switch and send a coded response it it's a high or a low
These are Vivint sensors I’m a beta test house and trying to save money for customers, not in it for money. I’m not sure yet until I see the electronics, but they have a magnet, so my first bet is a resistive sensing circuit changed by Mag force.

I know there recessed door mag setup has a glass tube with a wire in it, my customer explained one the sensor we sent him had a broken glass tube so I’m still in the process of discovery.
kv
 

Thread Starter

killivolt

Joined Jan 10, 2010
805
Here's a look at one I've been playing with I'm using some parts off it.
View attachment 209198
We get some false positives, open when closed. If a reed switch is mechanical explains a lot. Eventually they would break over time I would think. A resistive circuit or Hall effect seems more the way to go rather than a mechanical. I’ll have to google some on their operation.

kv

Edit: Ok, then mechanical. Inert Gas prevents carbon break down, the glass tube holds it in preventing exposure to oxygen. Simplistic very functional I would suspect it would operate thousands of times unless there was a manufacturing defect, most likely would present itself early on vibration could create false positives, such as during a storm if a window or door might shake.
 
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Thread Starter

killivolt

Joined Jan 10, 2010
805
I just had the system installed I plan to monitor vibrational issues that might trigger a false alarm. Like how violently someone closes a window or not. Tactile sensors won’t or shouldn’t show false positives. But still unsure, I still lean to Hall effect if anyone says that isn’t the way to go let me know. More expensive possibly but seems more logical.

kv
 

be80be

Joined Jul 5, 2008
2,057
Vibration it take a lot of Vibration they close at a inch away and stay closed.
bigger the magnet the better they close.

And if the door or window has moved that much someone done broke in anyways LOL.

I don't think life will be a problem probably out live most people
I never seen a bad one just missing magnet, And the wired ones
would have wire cut but the reed was always still in good shape.
 
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Thread Starter

killivolt

Joined Jan 10, 2010
805
Got my Buck from china today, going to do a little cov19 cleaning with gloves.

kv

Edit: Decided to just let it sit in bowl then charge my 12v gel cell and print the new housing. I’ll mock a door window installation and test it over time, recording any events If any.
 

Alec_t

Joined Sep 17, 2013
12,315
The only problem I've ever had with a reed switch was the reed becoming permanently magnetised (by a moving magnet on rotating machinery....not a window :) ), thus keeping the switch 'on'.
 

Thread Starter

killivolt

Joined Jan 10, 2010
805
The only problem I've ever had with a reed switch was the reed becoming permanently magnetised (by a moving magnet on rotating machinery....not a window :) ), thus keeping the switch 'on'.
Never even thought about that, polarization. Now it makes me wonder if a hall effect or tactile sensor would be better than the reed switch. So, most of the time we have a false open, but that could be the last ”State” reported to the control panel before it went offline, or it literally stopped closing which would be opposite of the polarizing effect as you stated, permanently open, that would be weird.



kv
 

Phil-S

Joined Dec 4, 2015
224
Hall switch is a cheap option but you need to choose the right one.
Omnipolar, bipolar, momentary, latching.
Advantage over reed switch is clean output, reed will need signal conditioning.
Very low power versions good for battery if sampling rate not a problem.
Simple CMOS logic chip will convert momentary Hall into a latching version or use a simple MCU to do it all.
 

Luregasy

Joined Jul 23, 2020
1
The only problem I've ever had with a reed switch was the reed becoming permanently magnetised (by a moving magnet on rotating machinery....not a window :) ), thus keeping the switch 'on'.
Hi Alec, I have a lot of experience with reed switches and I have never seen a reed switch stuck closed unless the reed it's been extremely over loaded or hit by lightning don't forget they can only handle low current loads. But magnetism will not affect the way it works.
 

pbrunnen

Joined Dec 30, 2017
9
Hi Alec,
I can say from experience that magnets and reed switches have been and still are the standard in the security industry since the early 90s. The biggest advance has been balanced switches to prevent people from attempting to fool the switch with a separate magnet.
Example video on youtube
 

marcf

Joined Dec 29, 2014
260
Normally open(NO) and Normally closed (NC) are terms used to define the states of switches, sensors or relay contacts under when its coil is not excited.


In a security or fire alarm a closed protection loop the way to go. If an open occurs either from an open door or a break in the wiring, an alarm is initiated. This would entail the use of NO (closed when the magnet is present) reed switches.

Another configuration is to use NO C NC (form C) switches. These switches are connected in a 2 loop configuration. The NO (Closed when the magnet is present) monitors the loop, while the NC (Open when the magnet is present) insures that a short would occur under an alarm condition. The advantage of the form C switch is that an alarm condition may be sensed if the system is "In Trouble", as the alarm monitoring device can 'see' both sides of the loop when it is open (in a trouble condition).

When the protection loop is open a system that uses Form C reed switches, a trouble condition is reported rather than an alarm.

NFPA 72 requires that a system NOT report an alarm on a trouble (open circuit). The same would be good idea for a security system.
 
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