trafic signal:-help

[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.

 

[Misterbenn]

a second year student at what clown school? how can you be new to the feild of electronics and yet a second year electronics student! what is the world coming to!!

firstly a lazer is a stupid idea no only do you have isues with blinding small dogs and rodents but a leaf could set it off, or a small blinded dog for that matter. you also have the problem of amarican missiles mistaking the lazer as a target and blowing your little road junction to kingdom come!

most road sensors use electro magnetic induction, a big coil of wire when a car moves onto it, it creates an electromagnetic field or sumthin like that.
if you want to avoid major road work you could use a IR movement detector, one that one pick up small objects like cats or people but looks out for big hot objects like cars.
or you could use the far simpler option of two pressure pads / tubes, the kind they use to monitor motorist numbers on various roads.

and durr a counter, you could use anything from a PIC to a 555 timer depending on how accurate you want it. tho the advantage with a pic is that it could store mutiple results.

 

[mictester]

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.

.

A Laser won't work - it will be interrupted by anything passing (not just vehicles). Detection on roads is done in four ways:

1. Pressure switches - these were gas-filled rubber tubes placed across the road surface, and the gas squeezed out by passing vehicles was used to operate a switch. These were used for many years, but were unreliable and expensive to replace. They are now seldom used.

2. Inductive loop - modern vehicle detectors energise a loop of wire buried in the road surface with a low frequency RF signal (usually 80 - 120 kHz). A vehicle passing over the loop will alter the loop inductance, and RF energy will be absorbed by the target. This energy loss is detected, and thus a vehicle is detected. The most accurate and reliable type of vehicle detection, but requires slots to be cut into the road surface to bury the detection loop.

3. Microwave detector - the area approaching the junction is flooded with low level microwave energy and monitored by a microwave receiver. Standing wave patterns are set up. A target moving in the microwave field causes doppler shift of the signal received, and thus a moving vehicle is detected. Fairly complex, but doesn't require digging holes in the road, and can be quite accurately calibrated.

4. Passive infra-red detector - works in a similar manner to many burglar alarm detectors. Looks for engine heat. Simple but quite unreliable!

Hope this helps

Mike

 

[stevez]

My old favorite was the ultrasonic method. Sensors were mounted directly over the vehicle location. Apparently the change in timing of reflected sound was significant enough to provide reliable detection. Ultrasonic or not I could hear it pinging away and found it quite irritating. They did seem to work though maybe not well with motorcycles.

 

[checkmate]

a second year student at what clown school? how can you be new to the feild of electronics and yet a second year electronics student! what is the world coming to!!

During my university days, first year students were studying common engineering subjects. I did not even touch a soldering iron until well into 2nd year.

 

[aibelectronics]

During my university days, first year students were studying common engineering subjects. I did not even touch a soldering iron until well into 2nd year.

yeah, I do agree with you. You can be a 2nd year engineering student and still be relatively new to electronics. my first constructional work was in 3rd year which was an astable multivibrator. It was so HARD and the schematic was so intimidating , but thereafter things began to move very fast as more and more complex schematics were encountered.

 

[audioguru]

On my very 1st day in university I had to be very diplomatic with the prof (no, he wasn't a Canadian):
Sorry sir, are you using an NPN transistor in your common emitter amplifier with the negative supply for its collector load resistor? Shouldn't the transistor be a PNP, or shouldn't the supply be positive?
Sorry again sir, wouldn't the transistor linear amplifier work better if the transistor had some base current?
Sorry again sir, Shouldn't the frequency compensation capacitor in your 10:1 'scope probe be adjusted to show flat-tops on the square wave (like my 'scope at home)?

Duh! There is nothing like teaching the teacher. I was way ahead of him. He was replaced soon. :lol: :lol: