low cost obstacle detection circuit

[varuntejavarma]

Hello,

I have to design a circuit for a device to detect any motion in front of the device upto 2 metres. I have tried with Ir reflection sensor. but couldnt acheive the range. so, I found out a circuit in internet which works on passive detection of shadows.

**broken link removed**

so, basically it takes in the ambient light and when there is a obstacle in front of the sensor, output is triggered. As mentioned in the circuit about using L14F1 as sensor, I could not get that part where i am living. So, I used a anormal phototransistor with some black sheilding around it. It seems to be working onfor 40 cms.

1. which type of sensor should i look out for. what are the specifications that i need to look for this application( detect fast change in light)

2. My major problem is I do not know if this circuit works properly for fast light changes. I need to drive a dc motor at output for 5 sec whenever the sensor detects a movement upto 2 metres.

3. Is there any other kind of low cost and effective sensor or method for this kind of application??

any suggestions or advices are greatly appreciated

Thanks in advance

 

[Genovator]

Have you tried ultrasonic sensors?? They are low cost and can measure upto 3m of distance with 2cm tolerance..

https://www.google.co.in/#q=ultrasonic+sensor
https://docs.google.com/file/d/1_WX...Km7icUz_PtpB4ODkZtH9XrpIN/edit?hl=en_US&pli=1

 

[jiripolivka]

To extend the range of your light sensor, try to modulate the LED current by say 1 kHz, then use a narrow-band audio amplifier for photo-diode output signal. I achieved ~10 meters range by this.
Ultrasonic sensors can work, too, also by amplifying the returned signal t the ultrasonic frequency to get the range.

 

[varuntejavarma]

To extend the range of your light sensor, try to modulate the LED current by say 1 kHz, then use a narrow-band audio amplifier for photo-diode output signal. I achieved ~10 meters range by this.
Ultrasonic sensors can work, too, also by amplifying the returned signal t the ultrasonic frequency to get the range.

wow 10 metres?? are you talking about sensor with both TX and RX side by side or with TX and RX at different ends. BUt, I have already tried modulating the Ir led but did not get a good range. maybe some basic mistakes. thats why came up with the above idea.

could you please post your circuit diagram. It would be very helpfull for me to correct my mistakes.

 

[chuckey]

Have you tried to use a reflector and lens to focus the light on the detector.
Frank