How To Make Beam Break Detector

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Qasim Khokhar

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hi, i want to make an ir beam break detector. which detect any object between ir source and detector and give 5 volt output. i want to place my source at 10 feet away from detector please help me to build this kind of detector. i am attaching an circuit diagram which according which i develop an detector but its out put is not stable LED in circuit blink when TSOP receives any signal.

 

Do you understand the operation of the TSOP IR detector cicrcuit? If so, you know that you need a pulsed (38 kHz) IR source and it has an open collector output (with interal 100 kOhm pull up resistor). When modulated IR light hits the detector, its output should be low (< 500 mV). The output of the LM311 should be high in that case (LED = off). To get better margin, I would increase R2 to several kOhms as now the threshold of the comparator circuit is in the 250 mV range.
 


can you please describe it in more details , what should i do to avoid blinking of LED i just need steady "on or off"
 

The datasheet of the TSOP IR detector explains that its sensitivity drops low if it receives continuous IR light. The IR light must be pulsed at about 38kHz for a certain amount of time then a pause for a certain amount of time over and over as explained. It is to avoid interference from continuous lights, the sun and compact fluorescent light bulbs that blink at the same frequency. The bursts of pulses are similar to remote control data.
 

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