Rolling shutter/door sensor - Page 1
Forum section: electronics / projects

author: say2paul
author_rank: Contributor
timestamp: May 01, 2014, 06:45:38 am
content: I have got an industrial security requirement where we need to deploy a security solution to detect theft or burglary.There are so many sensors available for the same, can anyone suggest the best suited!Magnetic sensor - Reed switchProximity sensorUltra sonic sensorother sensorsI believe industry is using magnetic sensor but I can see a flaw i.e. anyone can put a strong magnetic field outside the door or roller shutter and can bypass the system.

author: han
author_rank: Frequent Contributor
timestamp: May 01, 2014, 07:13:34 am
content: For detecting opened door or, detecting theft?For the door sensor, reed switch is quite simple and robust..if you installed correctly Theft will not know where is it..for theft detection, the PIR movement sensor is unbeatable..

author: SeanB
author_rank: Super Contributor
timestamp: May 01, 2014, 09:55:25 am
content: Standard is a magnetic reed switch on the door. Simple, cheap and quite reliable. If you are concerned place 2, one on each side. It is hard to bypass them with a magnet without causing one of the switches to flip state. Inside PIR sensor is useful, though it can be defeated. Use a dual IR and microwave PIR, they are less prone to false triggering by heat sources.

author: say2paul
author_rank: Contributor
timestamp: May 14, 2014, 12:10:07 pm
content: Quote from: SeanB on May 01, 2014, 09:55:25 amThanks dear, adding PIRs will increase the cost.. looking for cost effective and reliable solution.Regarding adding another reed switch, anyone can bypass it by applying a strong magnet on both sides.See if we can brainstorm and have a better solution.

author: Kjelt
author_rank: Super Contributor
timestamp: May 14, 2014, 12:48:39 pm
content: For the shutter, perhaps use a sensitive short range Infrared Proximity Sensor perhaps with an IR reflective coating on inside of the shutter. The uC sensor algorithm should detect the change in proximity but also change in reflection (perhaps dual sensors).In order to break the system the burglar should have to place an reflecting object (mirror) directly on the right spot where the shutter was so since these are pretty cheap and you want high reliability and prevent false positives you place a larger amount of sensors on each shutter and detect if two or more change at the same time.You could also combine this with differently positioned pressure sensors where the shutter presses on these sensors.

author: nihilism
author_rank: Regular Contributor
timestamp: May 14, 2014, 12:49:47 pm
content: triple bias reed switch

author: Flump
author_rank: Frequent Contributor
timestamp: May 14, 2014, 01:49:00 pm
content: whats wrong with a mechanical micro switch or 3 ?it doesnt have to be mounted on the door,could be mounted inside above it etc,so would be protected from outside abuse.editsomethng like thishttp://www.ebay.co.uk/itm/10-Roller-Lever-Arm-Micro-Switches-AC-250V-HV-156-1C25-/331200116254?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item4d1d10b61e

author: SeanB
author_rank: Super Contributor
timestamp: May 14, 2014, 06:06:06 pm
content: To bypass a magnetic switch placed inside a steel magnetic shunt ( the door) a pretty strong magnet is needed to saturate the steel, and you have the problem of approaching it so that the reed switch will not flip state for a period. 2 switches next to each other is series will not be able to flip, as you both have the switch protected by the door and have 2 magnets that have fields to overcome. Most common way through a shutter door is a drive through, or simply to break the door with brute force. for a door the easiest is a pair of reed sensors top and bottom, and if you want get a concealed switch and place in the door jamb where it is invisible even with the door open. Roller shutters you have a switch each end, and back it up with either a set of IR beams across the inside, or a simple PIR on the alarm panel as well. works for doors as well in case somebody cuts the door apart.

author: SL4P
author_rank: Super Contributor
timestamp: May 15, 2014, 02:55:40 am
content: How about a simple close range reflective beam onto a movable part of the door. If the door is moved out of the path (opened or pulled) the alarm goes off. Design as an N/C circuit to detect wire breaks or other tampering.Add a PIR inside the area - to detect if someone cuts *through* the door without disturbing it's physical position.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: May 15, 2014, 08:05:39 pm
content: There are many levels to any form of security.Fundamentally any security can be broken; the point is to delay the attacker for enough time to allow detection of the attack and to allow an effective response. This is true whether we are talking electronic, physical or any other form of attack.What are you actually attempting to achieve?

author: SeanB
author_rank: Super Contributor
timestamp: May 17, 2014, 05:25:43 pm
content: I saw in a catalogue safety reed switches, which will open if they either are misaligned or if an external magnetic field is applied. Intended for use as machinery guards they should do fine as door switches.

author: David_AVD
author_rank: Super Contributor
timestamp: May 17, 2014, 10:38:28 pm
content: Yes, theft detection, theft deterrent and theft prevention are all different things.

author: RABeng224
author_rank: Contributor
timestamp: May 18, 2014, 01:28:53 am
content: Not sure if what your talking about is motorized if so, there should be a limit switch which tells the motor to stop running. You could tap off this limit switch to detect if the door has been moved from the closed position.