IR sensor

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Re: IR sensor

Postby kl84 » Thu Mar 03, 2011 1:53 am

You're build a line follow robot on a black surface with black tape? How?!?
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Re: IR sensor

Postby picpicpikapika » Thu Mar 03, 2011 5:44 am

No, I am not building line following robot I am building a car running on a normal surface (the rough surface), and there is a black colour tape at the end of my track, my car has to detect this tape and do something else.
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Re: IR sensor

Postby robosang » Thu Mar 03, 2011 9:45 am

picpicpikapika WROTE:Hi, I dun really understand...if I am not going to use other colour tapes except black colour one...and the runway for my car has only a black colour tape at the end...according to ober, the infrared intensity of black colour surface and normal rough surface to the receiver is the same...so how am I going to detect this black colour tape since no voltage difference(output voltage of the sensor) between this black surface and my track???


well, I don think ober say infrared intensity (reflected) of black color surface and normal rough surface is same. Instead, from my understanding, black color surface that reflect small amount of infrared is nearly same as nothing blocking the infrared emitter where the infrared is not reflected at all. And result in IR receiver does not have significant voltage changes. So, these difference is not big enough and stable enough to be detectable.

As long as 2 types of surface can reflect different amount of IR that is significant and stable along the same surface, you can differentiate it and further detect it.

Normally, this low cost IR is being used for line following, object detection where differences of IR reflection is huge enough. Example in line following, if the line is black color, the ground color should be white, green, or even red that I have seen before. It does not matter what is the color of line or the color backdrop, as long as it can have significant difference of IR reflected, you are good to use it.

Normally white and black is use because theoretically, black absorb all light while white reflect most of the light source.

Try it out.
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Re: IR sensor

Postby picpicpikapika » Fri Mar 04, 2011 8:12 am

Hi, thanks for the explaination...I get what you mean, the most important point is that once there are two different surface, the IR sensor will be able to distinguish them...previously I thought the track or runway I am using bring no effect to the sensor, but actually It reflects light as well but not as strong as the pure white surface. So, the vital factors now are the sensitivity of the sensor, and for me comparator need to be considered as well. However, my comparator is not sensitive at all, like what i mentioned in my previous posts, the logic works but not precise...I need big difference between non-inverting input and inverting input to toggle the comparator output...I am thinking of using LM339, but LM324 shouldn't be so unsensitive. Now, I am thinking of using ADC feature in my mcu instead of using comparator...it should be better right?
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Re: IR sensor

Postby picpicpikapika » Mon Mar 14, 2011 6:06 am

Hi, Shahrul I have left a comment in your PIC IR sensor website, can you please check it thanks a lot...
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Re: IR sensor

Postby picpicpikapika » Wed Mar 16, 2011 7:59 pm

Hi, can I know what are the perfect resistor values for IR receiver and IR transmitter?? I have tried to used 330 ohms for my transmitter and 47K for my receiver, but when I tried to put a pure white paper on top of the sensor the voltage only decreased from 4.5V to 4.0V. Is it the normal result?? I have tried with 4.7k for my receiver, the result was even worse, no voltage change at all when I place the paper on top of the sensor...can I know what is the problem?? thanks
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Re: IR sensor

Postby shahrul » Wed Mar 16, 2011 9:15 pm

picpicpikapika WROTE:Hi, can I know what are the perfect resistor values for IR receiver and IR transmitter?? I have tried to used 330 ohms for my transmitter and 47K for my receiver, but when I tried to put a pure white paper on top of the sensor the voltage only decreased from 4.5V to 4.0V. Is it the normal result?? I have tried with 4.7k for my receiver, the result was even worse, no voltage change at all when I place the paper on top of the sensor...can I know what is the problem?? thanks

Maybe you connect IR Receiver wrongly. IR Receiver is different, the long leg is (-) and short leg is (+). Maybe this is cause the receiver not detect the IR.
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Re: IR sensor

Postby picpicpikapika » Tue Mar 22, 2011 6:45 pm

Hi shahrul thanks a lot...I never use ir sensor before...now I am able to get around 0 volts when touch my hand on the sensor..really thanks a lot...
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