trafic signal

[ahtesham_rulz]

Hello,
I am a 2nd year electronics student. I am trying to do a simple project of counting the time for which a signal should be open. I have thought of placing a laser at one side of the road and a sensor at exactly the opposite, when a vechile crosses this laser it is blocked from reaching the sensor and at exactly the same time a device starts counting the duration of obstruction.

Can any one please help me out as for which devices to be used. Any other sugestion concerning this idea will be greatly appreaciated.

please : - I am just a new comer in the field of electronics.

[tgit23]

Sounds like an excellent idea.  You might consider using infrared instead of laser, or possible a sonic sensor?  Whereas the infrared would be invisible to the human eye, it wil probably require a sensor on the other side.  Whereas a sonic sensor may be capable of detecting a car without a sensor on the other side of the street.  RU looking to build from scratch parts or boughten parts?  (ie..  Component level building or puchase of pieces to build your idea?

[ahtesham_rulz]

thanks for the advice.

i am planning to build from purchased devices

[waferstar]

That is not difficult.
And easy to design and produce.
But I think firstly you should be ware of the disturbance from sunlight.
So you can use the software to avoid the disturbance.
Also if you need a long distance between the Transmitter and Receiver,you should select a good amplifier and also select a suitable Power of the Transmitter.


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Extract the software Code From Programed MCU

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www.waferstar.com
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[Shahriar]

Dear ahtesham_rulz

In my area this problem is solved in Traffic Lights.
My friends use some sensors which are similar to wires. they put them across the road and hide them.
they are sensitive to vehicles. If you look for these sensores then it makes everything very easy. using Laser or light is not good because of Sun light as others said. anyway, if you use IR then then it is possible that when people cut the IR, You mistake it with a Vehicle. but IR is much more better than Laser and light.

P.S. for your IR receiver use those Kinds that are not sensitive to Sun light. i.e. TV IR receiver. some kind of IR receivers are sensitive to Sun Light.

HTH - Shahriar

[audioguru]

I think that the sun emits IR, therefore how would they make an IR detector that isn't sensitive to IR? ??? ???

[Shahriar]

Dear AudioGuru

If You put your TV set somewhere in Sunlight you will see nothing happens to its IR remote control.
I have tested many IR receivers and have seen that some of them acts like a LDR when there is no IR Emitter. The best Receivers are TV IR receivers. they are much more expensive than normal IR receivers. some kind of them have Three Leads.

P.S. If you take a look at note section in Park-Aid Project, then You see that Author have the same Oponion.

"The infra-red Photo Diode D2, should be of the type incorporating an optical sunlight filter: these components appear in black plastic
cases. Some of them resemble TO92 transistors: in this case, please note that the sensitive surface is the curved, not the flat one."


HTH - Shahriar

[audioguru]

Hi Shahriar,
A black IR photodetector reduces its sensitivity to all light including sunlight. Sunlight also has a high amount of IR that can't be changed.
Many 3-pin IR receiver ICs such as the TSOP series, have an automatic gain control system that reduces their sensitivity if there is interference from ambient light, and interference from ambient IR from sunlight or continuously modulated compact florescent bulbs also operating at about 38kHz. To keep their sensitivity high, the incoming IR must be modulated with their tuned frequency for only a certain number of pulses, followed by a pause. ;D