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Help building an infrared break sensor

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georgetwo

Member
hi everyone
I was trying to build an infrared break sensor. i intend to use it to controle a door such that when the ray is broken, the door opens and closes when the ray is broken at the other side of the door. with this system, it will be possible to build a strict door such that the 'in' door will only open when you are going in and out door will do same thing. I can also keep record o how many people enters and leaves trough the door. thn controle circuit for this will not be a problem, All i need is a circuit that sends an uninterrupted infrared signal trough a distance of 1.6meters. If not possible what about laser?
 

AlainB

Member
A cheap laser pointing device will work with a photocell even twice the distance you need or more. But I don't know if it would stand a constant duty.
 
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georgetwo

Member
if i will be using lacer, how do i stop other rays of light form entering into the photo sensor while alowing the lacer beam only?

do you think the lacer beam will be steady for as long as there is Vcc in the circuit ? If no, how do i go about it
 

georgetwo

Member
if i will be using lacer, how do i stop other rays of light form entering into the photo sensor while alowing the lacer beam only?

do you think the lacer beam will be steady for as long as there is Vcc in the circuit ? If no, how do i go about it
 

birdman0_o

Active Member
Nice to see someone else from Montreal :)

George, hide the photocell in a box which the sun cannot hit.
What are you using for the counting, a uC? You could maybe take the IR path then.
 

Boncuk

New Member
I'd go for an IR barrier instead of laser just for safety reasons. The weakest laser is able to impair eyes forever which might happen if a child enters the room and turns towards the laser beam.

Use a TSOP34xx (Vishay) IR-receiver chip and use a transmitter sending bursts of high frequency pulse packets (30 to 56KHz). The IR-transmitter diode TSAL6100 (Vishay) is a well suited transmitter for extended range and has 130mW/sr (compared with "normal" IR-diodes of 5 to 50mW/sr). It can transmit 1,000mW/sr at 100µs on-time (at an If of 1A).

Since the receiver filters ambient light and additionally works with bursts of UV light it is immune to any other light source.

Using a counter you probably will use an MCU for the device. The TSOP34xx can directly be interfaced with a microcontroller. You might also generate the pulse bursts for the transmitter diode with the MCU.

Boncuk
 

AlainB

Member
Hi Mike!:)

Boncuk, I agree with you, there is a safety issue using laser.
 
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MikeMl

Well-Known Member
Most Helpful Member
Follow this thread, this one, and this one.

The IR receiver module that I referenced in my posts "locks" on to a continuous (no modulation) illumination from the IR LED chopped at 40kHz with near 50% duty cycle. The output from the IR receiver stays high (~4.9V) as long as the IR beam is unbroken. During a momentary break of the IR beam, such as waving your hand in front of it, the IR receiver output goes low (~0.1V) as long as the beam is broken, and then goes back high when the beam is reestablished.
 
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