Interactive led display

[Sparta]

Anyone know the interactive led display? It is like the led will turn on when the sensor detect the motion. Led will turn off when no motion detect. Anyone know what kind of sensor is suitable for this function? IR, PIR or other sensor? The range just about 20-30 cm enough.

[vinniewryan]

it depends on what it's being used for. This is more of an electronics circuit design question than a CCS question. Some people here might suggest you ask on another forum, or keep on topic to CCS, but I'll give you my professional advice anyway. If your device is going to be in a room where the lighting doesn't change, you can simply use a photoresistor for motion dection if you set it up right. Ir sensors also work, but I know you can just go to radio shack and buy a specific motion sensing unit for about 5 dollars. They detect heat signatures, I believe.

To set up a photoresistor, you would have to couple the sensor in a tube where very little light can directly hit the sensor. Put it in the corner of a room pointing at a light. When anything moves in front of the light, the photo resistor will resist the current passing through it, which can be detected by a microcontroller as motion.

To set up an IR motion sensor, you can do it a few ways. The first way is to have a sending unit pointing at a recieving unit. When anything passes inbetween them, the recieving unit will see the drop in recieved IR signal and this can be detected by a microcontroller as motion. The other way to do it would be to place an IR transmitter and reciever on the same unit pointing towards the room in a 30 degree fashion. This only works in smaller rooms. When anything moves in the room, the IR reciever will detect a change in the light it's recieving. This works even better if you use two IR recivers with an IR transmitter in the middle. Make sure there is something between the transmitting IR LED and the recievers to block the light from hitting the IR sensors at the unit.

\ | /
R |T| R

The lines above represent the direction each componant is facing. The R stands for Reciever, the | is something blocking light, and the T is an IR LED transmitter.

I hope this helps.
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Vinnie Ryan