entrance alert - Page 1
Forum section: electronics / beginners

author: darinsquared
author_rank: Contributor
timestamp: October 09, 2016, 10:02:38 pm
content: I want to set up a system to monitor traffic on a road that enters my yard ( I live in a rural area) for security purposes. I have two approaches off of one road. Here is what I am thinking. At a point before each entrance I put up a sensor that will detect if a vehicle passes by from one direction. I will calculate the time required to go by the second sensor. If the vehicle does not go by the second sensor in the allotted time a signal will trip an alarm (lights, horns etc...). It has to be able work from both directions i.e. sensor A starts the timer and sensor B stops it and visa versa. It is mostly required for night time operation.Here are some parameters:distance between sensors 250 metres, good LOSwidth of road to monitor 8 metresdistance to alarms 300 metres , poor LOSoperating temp -30 deg C -+30 deg CI am not sure which sensor ,PIR, laser, or ultrasonic would be best given the different parameters. I assume I will need to communicate between sensors and sensors and between sensors and alarm via RF.I have found ideas to how to use a laser trip wire or ultrasound sensors but what I can not find is a way to have the two sensors act as both master and slave.If this post is unacceptable feel free to remove it.In the future I may expand it to send a text message when alarm is tripped.I am very new electronics and arduino/raspberry pi so any help would be appreciated.

author: Ian.M
author_rank: Super Contributor
timestamp: October 09, 2016, 10:55:44 pm
content: Is there a public right of way for vehicular traffic actually *through* your yard?A sketch showing a plan of the road(s), your yard and the property boundary if its anywhere near the yard, with the locations you want to sense traffic at and activate alarms at would be worth a thousand words.

author: digsys
author_rank: Unknown
timestamp: October 09, 2016, 11:25:10 pm
content: To really simplify your input, I'd look at wireless battery powered alarm modules, either cameras or plain outdoor sensors. There are literally 100s to chose from,and many have long battery life. Just make sure you hide / protect them well. My ideal solution is to use a remote wireless IR camera with movement detection /triggering. I've made up several system in the last few months, and these work REALLY well. You have unlimited zone / duration / sensitivity triggers PLUS theyalready have many options for reporting ! AND quicte cheap. That way you also have visual recording of all movements.Edit: For power / recharge, you can either use simple solar charger or a swap out system once a month etc.

author: darinsquared
author_rank: Contributor
timestamp: October 10, 2016, 01:22:28 am
content: to answer some of the questions. The road I want to put the sensor on is public, the access to my yard is private. I have considered snow so if I use an optical sensor it will be shielded i.e. in an enclosed mount for falling snow I have no remedy. Also, I think I would need to rule out laser sensors because I could not make the mounts stable enough against wind to keep them in line. I am leaning towards sound (microphone) or ultra sonic sensor.Burying a sensor in the road would be an option.I want to use this as much for a deterrent as system to notify me. i.e. if intruders come into the yard I wants lights and sirens to warn me and scare them away. So a camera system is not ideal.I will work on getting a diagram.

author: Ian.M
author_rank: Super Contributor
timestamp: October 10, 2016, 01:39:19 am
content: The problem with sensing traffic on the road, even in one direction only is you cant guarantee the same number of detections entering the zone as exiting it. e.g. consider two vehicles, one overtaking the other right at one of the sensors.Its even more difficult with two way traffic. The case that would most concern you is two vehicles full of crooks driving into the zone. One stops in the zone and the other carries on past a bit to check there's no-one around then backs up back into the zone. Unless both sensors are directional (ie can distinguish between entry and exit) you now have the same number of sensor triggers either side of the zone within the permitted time window so the system does not alarm.Unless you go for cameras with some very sophisticated image processing that can identify specific individual vehicles (e.g. number plate recognition) its fundamentally intractable.

author: Muttley Snickers
author_rank: Unknown
timestamp: October 10, 2016, 01:41:10 am
content: You may be restricted to locating any sensing devices within your own property boundary as I would expect that installing any equipment in, on or near a public thoroughfare may be frowned upon or perhaps even illegal in some regions, you may well get away with placing reflective photo electric beams across a roadway and mount the passive reflectors on a tree or post on the far side but the main beam units located within your boundary will still require power so maybe a small solar panel, charge controller, battery and an RF transmitter in a waterproof cabinet mounted alongside the beam RX/TX module would suffice in addition to an RF receiver back at the premises. I would be disregarding the road traffic altogether and focus on the boundary entry points alone, look at using Optex PE beams to monitor each individual point or even cover an entire front boundary including the driveways with a single long range set or stacked sets mounted on posts.If the residence already incorporates a security system with a couple of spare zones then these may be utilised along with a dedicated output for a buzzer or siren, some systems do have additional macro features such as pulse count and trigger zones so the final configuration may be tweaked in programming to suite your requirements depending on the particular system if indeed any, reed switches on entry gates would be the simplest and most reliable form of sensing that someone is approaching the premises and using activity or motion detection on external CCTV cameras to trigger an audible alert is a waste of time in my view, the feature itself is generally best used to add either alarm or activity events to the DVRs log with time, date and camera numbers for rapid review as opposed to searching through hours of footage for a single event.Cameras and DVRs that utilise motion or activity detection in an outdoor environment can and will be triggered on any movement within the designated detection grid, this includes animals, insects, rain, hail, moving trees and leaves, reflected light and shadows, you name it everything gets picked up and either logged or reported depending on the configuration and cameras that incorporate infra-red illuminators are the worst offenders as they readily attract moths and in turn cobwebs, spiders can be a huge annoyance and shifty at times.As Ian recommended earlier a picture or diagram of the layout would assist immensely in addition to any information on existing systems that may be present, one final consideration is that vehicles leaving the site may drive other occupants mad with a buzzer or siren sounding frequently for no valid reason or occurrence.

author: darinsquared
author_rank: Contributor
timestamp: October 10, 2016, 03:00:46 am
content: here is the basic image. I chose to go monitor the main road (which is legal in the area) because it has a shorter distance to monitor than the three individual accesses.I have no security system as I am 50 km from the nearest law enforcement it would be useless thus I want to scare off potential trespassers.I never considered vehicles leaving setting off the alarm as I planned on only using it after dark. I would need to incorporate a way to arm and disarm the alarm.I looked at the Optex PE. They are infrared so would they not have the same problem with insects you mentioned. Also, I am aiming for a low power system working off of batteries/solar as the cost to hard wire the Optex system would be prohibitive.

author: Ian.M
author_rank: Super Contributor
timestamp: October 10, 2016, 03:50:13 am
content: As I explained above, detecting road traffic then distinguishing between those that carry on past and those that don't is a non-starter. Your remaining choices are detection at the entrances or broad area detection within the yard. The latter is likely to offer poor coverage and be prone to false alarms.If you want to discriminate effectively against wildlife etc and only detect vehicles,. the best option is an inductive proximity loop. However the widths of the entrances are such that multiple loops would be required for each. As such, multiple IR laser beams are probably a better bet, at heights that will pick up vehicles or people on foot, but not small mammals. Assuming there is power available at the shop, a wired installation will almost certainly be cheaper than a reliable solar powered installation even though you'll probably have to hire a slot cutter if the yard surface is all concrete, or put in some tall poles and run catenary cables. You don't want thieves targeting the solar panels and batteries of your security system!

author: Jeroen3
author_rank: Super Contributor
timestamp: October 10, 2016, 07:34:08 am
content: Radars. Mobile traffic light use them.Some roads use them to dim street lights when there is no traffic.

author: bookaboo
author_rank: Frequent Contributor
timestamp: October 10, 2016, 08:12:58 am
content: For traffic analysis I've used an old school magnetometer like these:http://www.speakesensors.co.uk/If buried in a waterproof box in a solid location they are totally immune to weather conditions. They dont need much in the way of external circutry to work but you need a circuit/processor to intereperte the frequency change caused by passing vehicles. Also theres drift to account for as the magnetic field changes naturally over time. Using one of these sensors you can actually detect when a vehicle stops within 10 m of it instead of driving on, again thats a software problem.

author: tautech
author_rank: Super Contributor
timestamp: October 10, 2016, 08:36:25 am
content: Quote from: darinsquared on October 10, 2016, 01:22:28 amNot necessarily, point to point invisible laser can reach along your road frontage covering all three entrances, only a LV power is needed at the transmitter end and LV power and the switched pair at the other, all quite doable with light duty telecoms type 4 core cable. There's no reason the transmitter end that only needs power (unless you want a tamper circuit too) can't be supplied from a separate PSU to the one that supplies the receiver.Then just a night switch or a dark sensor in either the receiver power or switched pair can give you the control you need.A P to P pair I installed years ago had a diffusing lens that spread the beam so that exact alignment was not critical and we put them in a sturdy steel box welded to a steel pole as wind and local railway vibrations were factors we had to consider.Care with alignment to get the best possible result gained the best tolerance against poor weather and bird triggered false activations. Sorry I can't remember the brand but it's still operating at a local business after 30 odd years.We installed 2 sets and IIRC they were 50 and 100m units.

author: digsys
author_rank: Unknown
timestamp: October 10, 2016, 10:41:46 am
content: ONE more option that I came across many years ago while doing security systems for precious metals / jewellery manufacturers.I was invited back to a chinese fellows home to see what options he had for security. He had a LOT of gold and sliver stored there.When I arrived, I noticed 2 wild dobermans safely(?) locked in the back yard, but NO other security. I queried this but got no reply.Upon entering, I was confronted, at the end of a short hall, by an 80+ year old grandfather sitting in a rocking chair and holding a loaded double-barrel shotgun.OHDo you have a spare old grandfather? Seems pretty effective and simple ! :-)

author: Jeroen3
author_rank: Super Contributor
timestamp: October 10, 2016, 10:50:35 am
content: Quote from: AcHmed99 on October 10, 2016, 10:42:04 amYes.

author: Muttley Snickers
author_rank: Unknown
timestamp: October 10, 2016, 11:26:24 am
content: Whatever method the OP decides upon I would be pretty confident in stating that it wont be a cheap fix given the distances involved, if the system is to be installed in a permanent and reliable manner then without question underground cabling and conduit would be my preferred approach.Even just the installation of concreted steel posts for either the PE beams, solar gear or other alternatives would be a major outlay on its own accord let alone the value of all the other devices and equipment required.

author: Brumby
author_rank: Unknown
timestamp: October 10, 2016, 10:26:01 pm
content: There are a number of ideas suggested here, each with their pros and cons - but I would like to float the idea that you might be able to use more than one idea to cover the area.If you were to have multiple sensors, the triggers could feed into an Arduino/Raspberry Pi (since you mentioned them) where a simple(?) program could determine if the alarm needs to sound. This would allow a lot of freedom to deal with master/slave issues, timing, sequences and to fine tune the system after implementation. Keep the sensors and links simple, for maximum reliability and ease of troubleshooting. Let the 'cleverness' reside in a central, secure point.As for the sensors, with the distances involved, it would seem to me that solar powered sensor stations with back to base RF links have the greatest appeal.Just one last thought .... While I'm a fan of lasers, I'd avoid having any laser beams that extend outside any private property. The risk of eye damage to the public may be low - but if there is no laser energy out there, the risk is zero. I might be a bit overcautious on this - but that's how I travel.

author: darinsquared
author_rank: Contributor
timestamp: October 11, 2016, 12:34:43 am
content: Quote from: Brumby on October 10, 2016, 10:26:01 pmWhat you describe is basically what I want to accomplish. I just do not know what is the best sensor type. I did not consider the issue with a laser.Just to clarify this road is seldom used, in fact in the winter the only reason it is used is to access my property or my brother's property nearby.We have not had any thefts yet but a short distance away, closer to a main highway, over half the neighbors have had thefts at least once in the last 5 years.

author: Muttley Snickers
author_rank: Unknown
timestamp: October 11, 2016, 12:47:16 am
content: Photo electric beams such as the Optex sets are completely invisible to the human eye and you would be hard pressed to even see them when viewed through a digital camera lens, I have been installing these and many other security sensors and devices for well over 25 years and the PE beams in particular for perimeter protection are the best option, the big question is what is your proposed budget for this application ?.

author: bitslice
author_rank: Frequent Contributor
timestamp: October 11, 2016, 04:13:36 pm
content: Quote from: Jeroen3 on October 10, 2016, 07:34:08 amThe plus side of radar as a sensor is that doppler shift tells you in which direction the object is moving (and its speed - ie is it going fast enough to be a car?), a PIR is only sensing movement across a lens.For this app I'd use a combination of both, laser/ultrasonic is a bit flaky outdoors. Although a magnetic sensor in the road surface would cut out a lot of false animal triggers

author: Brumby
author_rank: Unknown
timestamp: October 12, 2016, 12:22:36 am
content: Quote from: bitslice on October 11, 2016, 04:13:36 pm... including people.This is why I suggested multiple types of sensors with some logic assessing detections.

author: tautech
author_rank: Super Contributor
timestamp: October 12, 2016, 12:41:58 am
content: Quote from: blueskull on October 12, 2016, 12:32:49 amProblem with doppler that detection is non-discriminatory, not something you want in an outdoor environment.For the OP the likely best option will be an above ground point to point beam spanning all 3 entrances or in-ground loops but they won't detect foot traffic.

author: C
author_rank: Super Contributor
timestamp: October 12, 2016, 01:48:56 am
content: I go with lots of different types of sensors.The best choice would include video if for nothing more then to try to catch the problem or false trigger from other sensors.So as an excuse to play you might look at something like ZoneMinder on a blackberry to record events.In the video, look at object tracking, it's different from motion sense. In the same thought, quick object change. If camera is pointed at road, a car hides what the camera normally sees in a large area quickly, here size matters.With future play coveredNote that garage door safety sensors are cheap. Might work some places as is but could be case and optics for better insides.Think of putting a hose across road like traffic counters & gas stations use to have. This could be a good or bad idea even if not connected.How about something like sensing active rfid tags across the road. Alarm on Loss of tag read. The active tag could reduce power to very low detection level.

author: tautech
author_rank: Super Contributor
timestamp: October 12, 2016, 02:01:31 am
content: Quote from: C on October 12, 2016, 01:48:56 amYep. that's definitely worth considering IF you have a hard surface pavement, not one with lots of little rocks to cut/puncture the hose.Then you only have one sensor and the capability to put it wherever you like.

author: Muttley Snickers
author_rank: Unknown
timestamp: October 12, 2016, 02:43:56 am
content: Two star pickets, some decent fishing line and a cow bell, that's all I have to offer up today.

author: bitslice
author_rank: Frequent Contributor
timestamp: October 12, 2016, 02:50:04 pm
content: Quote from: Brumby on October 12, 2016, 12:22:36 amOP only requested the detection of traffic?I'm assuming that this is one of those rural locations where people wandering around would be unusual, and that discounting the odd moose/deer is a relevant requirement.Besides, if someone is on foot they may be wandering off road, so he's going to need to detect those closer to his property regardless of what he uses for monitoring the road

author: Brumby
author_rank: Unknown
timestamp: October 13, 2016, 01:27:22 am
content: Pedestrian traffic is still traffic ...But yes, as unlikely as it might be, people could have parked down the road and wandered up to the property.I suppose the best thing we can do is keep throwing ideas around and the OP can see what might work for him.

author: digsys
author_rank: Unknown
timestamp: October 13, 2016, 02:29:03 am
content: As can be seen the number of incident variations posted, and enviromental considerations (snow etc), this is unlikely to ever be 100% solved / accurate.It's looking like my suggestion of - grandpa with a shotgun - is probably the most relaible.

author: Brumby
author_rank: Unknown
timestamp: October 13, 2016, 03:25:34 am
content: Quote from: blueskull on October 13, 2016, 01:42:19 amLOLA little less discriminating than grandpa with a shotgun - but lower maintenance cost.

author: NottheDan
author_rank: Frequent Contributor
timestamp: October 13, 2016, 04:07:09 am
content: My employer uses a software-based tracking system that seems to work well for them, something likethis. (not affiliated, just the first example I found)

author: Jeroen3
author_rank: Super Contributor
timestamp: October 13, 2016, 05:33:10 am
content: Quote from: blueskull on October 13, 2016, 01:42:19 amBest solution. Even works when the power goes down. Although you might want another brand.

author: darinsquared
author_rank: Contributor
timestamp: October 13, 2016, 11:19:30 am
content: Quote from: Muttley Snickers on October 12, 2016, 02:43:56 amI was contemplating something like this but a little more technical. Using a fishing line connected to a switch that would sound an alarm if the line is "disconnected". If would need to be physically reset everyday.For one entrance I am now considering a gate. When the gate is closed it will line up with a proximity switch shutting off an alarm. I need to figure out a way to open the gate remotely for guests and open it from a vehicle with RFID (or similar method). Both will have to disable alarm. All other entrances are too wide for this method.I prefer an invisisble barrier. I am playing with using a straight sound sensor on both perimeters. If my intruders drive electric cars I might be hooped.

author: C
author_rank: Super Contributor
timestamp: October 13, 2016, 12:48:30 pm
content: According to Vishay you can do 30m for a beam break IR sensor.No idea how wide your other entrance(s) are, but sliding gates do close very large widths. Gate slides behind current fence as it opens.Some the gate does not touch the ground. Some have support wheels on gate. Some hang from overhead beam. Can use cable to pull open or closed.