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Low cost long range motion detection

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varuntejavarma

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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. Then, 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 upto 2 metres with narrow detection)

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??

I am a beginner to this field. I am willing to learn by doing. so,any suggestions or advices are greatly appreciated

Thanks in advance
 
The shadow detector has some serious geometric constraints. What happens if the lights go out, another light is turned on, or a light source moves?

Passive reflective IR should work at 2 meters. How did you conclude it wouldn't work? What was your design?

There are also passive IR detectors readily available on the market to detect movement. Why not buy one and study how it is made?

John
 
Passive reflective IR should work at 2 meters. How did you conclude it wouldn't work? What was your design?

I have tried reflective type by modulating the signal. I used TSOP56 at reciever and two 555 timers at transmitter to send pulses of 56 khz signals. But the output led is ON irrespective of the obstacle. it goes OFF only when i remove the ir emitter off the circuit. I have also sheilded the ir emitter. but doesnt work. Do you have any idea about my mistake. I have attached my circuit. plz let me know.


There are also passive IR detectors readily available on the market to detect movement. Why not buy one and study how it is made?

I have already thought of PIR sensor. But, I need to trigger the output when someone passesby the device with the sensor having narrow detection angle. But I think pir sensor works with a wide detection angle or ?? and also the main problem is they are expensive and I am planning to build a low cost circuit.

The shadow detector has some serious geometric constraints. What happens if the lights go out, another light is turned on, or a light source moves?

After trying Reflective Ir sensor, I have checked this link and found out that it uses a simple photosensor which is low cost and needs low power consumption.
https://tronixstuff.com/tag/glade/
I also want to build a circuit for the same application. so, thats i why I thought of using the shadow detector circuit.

But, I have made these assumptions by myself. I do not know anything for sure. please correct me if I was wrong about anything. I am glad to learn

Please let me know a better approach for the application

Thanks
 

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This is a file containing about the circuit and some description which is used in the device. I am confused and could not undersatnd properly what is going on. . It would be helpful if someone could suggest me a solution with my problem
 

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It sounds like your detector may be getting too much scattered light from the emitter to ever turn off. How were they arranged physically? In a similar project, I had to have the emitter in front of the detector. An opaque tube around the emitter may be necessary. I used a 6-mm aluminum tube for that. A paper tube covered with black vinyl tape will also work. Can't find a picture of that project, but here is a rough drawing:
upload_2014-7-31_10-7-6.png


John
 
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