I have to design a circuit for a device to detect any motion in front of the device up to 2 meters. I have tried with IR reflection sensor, but couldn't achieve the range. Then, I found a circuit on the internet which works on passive detection of shadows.
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 a normal phototransistor with some black shielding around it. It seems to be working up to 40 cm.
Which type of sensor should I look for? What are the specifications that I need to look for this application (detect fast change in light up to 2 meters with narrow detection)?
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 up to 2 meters.
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 and advice is greatly appreciated.