Ali Az Zobui

Hi every body,

I have a robotic project and i am stuck with the IR detectors. My problem is that the detectors(photo diodes) are beung affected by any source of light.

Anybody has ideas? I will thankfull for help.

Sceadwian

This topic has been covered ad nauseam in the forums. The simple solution is to use a capacitor to DC isolate the photo detector output. The more functional solution is to use a single carrier frequency for the transmitter and as sharp a notch filter as possible on the input. TV's, PC monitor's, incandescent light bulbs, florescent bulbs, many LED clocks are all source of modulated light noise.

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Ali Az Zobui

Ok? thanks for the information.

One more thing, i am using PIC microcontroller to control the robot, i am stuck with the idea of HOW TO MAKE THE MICROCONTROLLER "UNDERSTAND"
THE INPUT SIGNAL, in other words, i want to measure the frequency of that signal so that the proper decision is made by the microcontroller since the robot has two IR transmitters (front and rear in order to detect front and back obstacles) , the result is to have two signals with two frequencies.

I hope that the idea is clear.

I am very thankfull to be helped.

Wingmax

Hi Ali,

My suggestion is- the general idea is to utilize the Timer function in the PIC micro. Set the Timer to counter mode.
Trigger counting and stop count in specific time. Say 100 nS.
Read value in TMR register.

Be sure to adjust the time so that the TMR register will not overflow. because it'll overflow after 255.

Since what you want is to disdinctguish between 2 different frequencies. So by reading the different values in the TMR register will pick the frequency you want.

There are other methods to count the freauency. You can use timer interrupt etc. But try this one, it should work.

Hope this help

Regards,

Sceadwian

So use two frequencies with two difference bandpass filters, just make sure the frequencies are as far apart as you can manage conviently.

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