• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

presence sensor

Status
Not open for further replies.

bogdanfirst

New Member
i need a circuit :D :D :D wich would sense if there is someone is in a room... :x
the room is about 3x4 m and 2,3 m hight......
i thought of something like an oscilator circuit and have a wire tied to it.
when someone comes in the room the oscilator's frequency changes and it triggers a circuit.... :p
i am waiting for suggestions and :idea: (ideas)
 

kinjalgp

Active Member
A PIR (Passive Infrared Sensor) can detect presence of Human Beings in its surroundings. It is a specialised photo-diode with in-built filters and amplifer which detects only human beings (not cats and dogs). It has 3-pins namely Vcc,Ground and output. The output pin goes high (+5V) as soon as any human body comes in its area of operation.
For more info. on PIR search "PIR sensor" in www.google.com
 

bogdanfirst

New Member
i heard about these devices......
i would be glad for some types of devices and datasheets...
but sitll i remain at my idea, with an oscilator, because i think it would be hard to get those devices.......
i also have some circuits wich can sense by putting ur hand near them, i even transformed one touch sw in one, by putting a copper plate to the sensor and it workes if u put ur hand near it.......
but i nedd soething for a room....
 

bogdanfirst

New Member
i know, but sitll i asked to all the shops i know and they dont have, so i will have to use a conventional method.....
finding electronic components here might be a tricky job in my town, it's small....and to go somewere else, i dont have time....
so i still need some conventional method
 

hsvgtsr1

New Member
ANY SECURITY SHOP WILL HAVE PIRS EVEN ELECTRONIC STORES. THE BEST SENOR TO USE WOULD BE A DUAL TECH SENSOR BE SURE NOT TO POINT IT AT THE WINDOW FOR IT CAN CAUSE FALSE ALARMS.

IF YOU NEED TO KNOW ANY MORE ABOUT SECURITY ASK ME AS I AM A SECURITY TECHNICIAN
 

bogdanfirst

New Member
Thanks.....
i went to a security shop, but they told me that they dont have some available at that time so, ill wait a bit....
anyway, are there some that work on a longer range, something like 10-15m, i want to use for a garden to light up when someone comes out?
 

mechie

New Member
PIR detectors

PIR units are available to work upto around 100m and are used for site perimeter security, they may be called "curtain detectors" as they see a very narrow field and work as electronic 'curtains'.
They are a bit pricey though!

Maybe an active IR beam would be cheaper over a long range at home.
 

hsvgtsr1

New Member
IN MY EXPERIENCE AS A SECURITY INSTALLER IR SENSORS ARE EXPENSIVE AND NOT NESSESSARY INTERNALLLY AS THEY CAN BE AVOIDED. THE UNITS BEING VISABLE MAKE IT POSSIBLE TO EASILY STEP OVER THE FIELD. PLACEMENT IS ALL IMPORTANT AS WIND, INSECTS AND THE SUN CAN EASILY SET IT OFF. BEST PLACEMENT IS A CORNER BECAUSE IT GIVES 90 degree VIEWING ANGLE, FACING THE DOOR YOU ENTER THROUGH AND NOT THE WINDOW. YOU CAN STILL GET AN ORDINARY CHEAP SENSOR AND ASK FOR A CURTAIN LENS BUT THIS WILL ONLY GIVE A NARROW FIELD OF COVERAGE, FOR EXAMPLE ALONG A WALL. BUT THE BEST THING IS TO BUY A SENSOR THAT'S RANGE IS SUITABLE FOR THE ROOM, IF YOU GET A SENSOR WITH TO MUCH RANGE YOU WILL GET DEAD AREAS UNDER THE SENSOR.

AS ALWAYS EAGER TO HEAR OTHERS THOUGHTS :D
 

Mat

New Member
Passive infra- red

These sensors nowadays are ten a penny, i have used them very effectively in my properties, i have made homebrew alarm systems since the late 60's that were effective, now the availability of the small pir is available to anyone cheaply, the security installer claims he can step over a heat detecting pir i doubt it! also he said they are visible and can be avoided, not likely....the pir is very effective used as say security lighting they come on as someone approaches, using the pir internally will sound an alarm once entry has been breached the LDR ie light dependant resistor or PCC photo conductive cell had these step over properties the security installer mentioned, but were still an effective deterrent even though false alarms were frequent, the pir system is reliable and apart from leaving your pet bear in the room when you leave your premises unattended not much usually sets off the alarm except intruders.
 

hsvgtsr1

New Member
There are many ways in which to avoid a pir sensor and I have seen it done many times in commercial buildings part of my job is repairing damaged systems. Iv'e also attended many residences where inexperienced techs have placed sensors in areas where it can be set off by the outside elements, so I know what I am talking about when it comes to the dangers of placing your trust and your hard earned money in a pir security sensor. there is nothing in this advise for me other than doing the right thing by someone. Benefit from my experience because someone who's just after your money will not be this honest with you!!!!!!!!!
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top