Need Help: Sensor to be used in Car Racing Project

[abo0badr]

I need help Creating a small project for a friend of mine. By the Way my name is Ali and I am a fresh Graduate of a Bachelor degree in Computer Engineering.

I just need help to decide which sensors are the most precised to be used in this Car Race Project. By the way this is a real cars racing project.
I just made an image here to show how the rules and regulations of the race. or in other way, how the problem flow is

The race will have only TWO CARS to race, I know this is a simple project for some of you; but i am not sure about what kind of sensor to use that can detect the car movement.
The race is a Time Lap Race, with only one Track for the same cars, it means that there is no over-taking from either cars, CAR1 or CAR2. The start line of CAR1 is other than the start line of CAR2, there will be a timer to detect the winner time (But don't care about it, I got this). lets say the race started, and of course they will run, when CAR1 passes through CAR2's Start line the timer will not yet stop (because it is only a half lap), same goes to CAR2 when reaches CAR1's Start line. when a Car Completes a LAP, the timer will stop there, either of the two cars, the timer will only stop when the sensor detects the car which left from its base (Start line) into the same line. I actually have the Idea how to know which car passes through, if it is CAR1 or CAR2, the problem is which sensor to be used to detect the car motion to stop the Timer from running. I had a problem in deciding sense I did not use any sensor that Can have a long range, and can sense exactly at a straight line, I already used a motion sensor but the one with an angle, maybe if I am not wrong it has a 90 Degree angle which can detect from 0 to 90 Degree, What I want is A SENSOR which can detect at a STRAIGHT Line, and can detect From a range of lets say 1 to 2 METERS. I hope some of the experts here can answer my Question. Please do help if you have an IDEA. Thank you So much

 

[(*steve*)]

The simple answer is to use a simple beam of light and look for that being broken.

Since the cars do not overtake (presumably if they do, the car that overtakes has automatically won) you can simply assume that the cars represent alternate interruptions of the beam.

If this is for real, then you would use multiple beams, placed far enough apart that a car can occlude them both, but a bird (or indeed a person) would not. You would look for both beams being occluded as an indication that the event is real.

You should be able to place these devices wither side of the track (say 10 metres apart).

Do the timing, or at least the triggering of the timers, using a microcontroller which can demultiplex the events for the two cars.

The major problem is when the cars get so close that they are no longer seen as 2 separate events. But if your rules say that this means the car catching up has won, then the issue is automatically resolved (albeit without the ability to get a timing).

 

[abo0badr]

The simple answer is to use a simple beam of light and look for that being broken.

Since the cars do not overtake (presumably if they do, the car that overtakes has automatically won) you can simply assume that the cars represent alternate interruptions of the beam.

First of all thanks for the fast response. Secondly, I already thought about the Beam you said. But what I thought about is like using a modified Infrared Sensor with a strong light, but the problem using infrared sensors is it has a small range as I think. then I told my self maybe IR is not the solution.

If this is for real, then you would use multiple beams, placed far enough apart that a car can occlude them both, but a bird (or indeed a person) would not. You would look for both beams being occluded as an indication that the event is real.

You should be able to place these devices wither side of the track (say 10 metres apart).

I think you mean I could put two beams of light on the 2 start/finish lines? I think that is the idea, but what are the possible receivers of the occluded light event?? how to determine if the light is being occluded or not.

Do the timing, or at least the triggering of the timers, using a microcontroller which can demultiplex the events for the two cars.

The major problem is when the cars get so close that they are no longer seen as 2 separate events. But if your rules say that this means the car catching up has won, then the issue is automatically resolved (albeit without the ability to get a timing).

Don't worry about the closeness of the cars, probably the 2 cars will start together and they will have a close number of acceleration for sure, and as you say, the rules of the race will be when the coming car gets 2 meters closer to the next car, that car will be announced the winner already.

 

[(*steve*)]

If you place the IR transmitter and receiver at the end of long tubes, you will have far less problems with ambient light.

If you modulate the light beam and look for the modulated signal (not the beam itself) then you will have a far more sensitive system less prone to interference from ambient light.

Use a laser and you could get a hundred metres of range if you wanted.

Each sensing station could consist of 2 beams. (maybe a metre apart) This means that something more than 1 metre long needs to interrupt the beams. This makes it less likely that some stray moth, bird, or piece of blowing paper will trigger the circuit.

 

[abo0badr]

If you place the IR transmitter and receiver at the end of long tubes, you will have far less problems with ambient light.

If you modulate the light beam and look for the modulated signal (not the beam itself) then you will have a far more sensitive system less prone to interference from ambient light.

Use a laser and you could get a hundred metres of range if you wanted.

Each sensing station could consist of 2 beams. (maybe a metre apart) This means that something more than 1 metre long needs to interrupt the beams. This makes it less likely that some stray moth, bird, or piece of blowing paper will trigger the circuit.

Now I get the real point of view from what you have said at the past comment. by using 2 beams to detect if the object passing by is a car or not.

But the problem will be the detection angle of the reflected light by the object passing through (the car). the Transmitter should have a good angle where the receiver will receive the reflected light.

hmmmm..I don't know what to say. If I will be using a LASER maybe the beam of it's light will be very high and can range longer than what I want, and may pass to other objects on the other side right? the problem is how can I now the right angle where the light will be reflected by the object passing through?

well, I will do my best. tomorrow I will go to the electronics shop and buy a China made Laser..haha..I have some photo-transistors left here from my old mobile robot project, maybe they can fit. Those are coming from Old ball mouses. Maybe they are good to try right?

Thanks a lot. I will give you a feedback as soon as possible.

 

[abo0badr]

But what do you say about using an ultrasonic sensor? is it good for this purpose or not?

or rather a metal Detector which can detect only Metallic objects passing through?

just thought About it.

 

[(*steve*)]

But the problem will be the detection angle of the reflected light by the object passing through (the car). the Transmitter should have a good angle where the receiver will receive the reflected light.

No, because the car breaks the beam. The transmitter (laser) is on one side of the track, the receiver (phototransistor) is on the other.

 

[abo0badr]

Yes. I tried just using a simple LDR (light dependent resistor)as the receiver of the beam..and it was a success. I was thinking of a better receiver but i think this LDR Is ok already.

The problem is when the distance is long between the laser and the LDR, i think the LDR will be a little bit wiggling or moving as a small movement of air may cause a big change in angle. But i am thinking of using a magnifying glass at the outer of a small pipe which will have the LDR stored inside it to keep darkness inside.
And then the magnifying glass will help to enlarge the light beam so that it will have a big receiving diameter

 

[abo0badr]

My problem now is how am I going to make a stopwatch timer that can count the lap time using just a simple PIC MICRO CONTROLLER and a 6 digits 7-segment display.

But actually i already made it. But i think the program is wron. It already displays the running time in milliseconds, seconds, and minutes..but the problem is while the different segemnts are switching, it flickers. Even if in the program I already put a 10ms delay only, still the switching between the segments is visible by human eyes.

 

[(*steve*)]

If you use a laser module, you will be able to get many metres without problems caused by low intensity. However you need to ensure that the receiver and (especially) the transmitter are very securely fixed so they don't move once set up.

it sounds like you are doing multiplexing in software. Can you do it faster?

 

[abo0badr]

If you use a laser module, you will be able to get many metres without problems caused by low intensity. However you need to ensure that the receiver and (especially) the transmitter are very securely fixed so they don't move once set up.

it sounds like you are doing multiplexing in software. Can you do it faster?

yeah thats the problem. I need something to enlarge the received beam in the receiver area..because the client wants it to be removable, since he will be using it in different racing areas. I am thinking of probably puting the receiver in a tube or pbc pipe to lessen the ambient light caused by the sun.

What do you mean by "Can I do it faster"??
I already finished the hardware and programming phase for a prototype or miniature only so that the client can take a look at the functions.

Next problem is which 7-segments I am going to use and which drivers that can drive big 7-segments.
My target segments is around 6 - 9 inches in size. So that it can be quite clear for human vision from around 10 to 20 meters away.

Do you have some ideas? it will be a pleasure listening to some of your comments.