could somebody help me!
I have apair of phototransistor and IrLED to enable me sense person entering and leaving a room. I would like to know occupancy by using updown counter fed by pulses from phototransistor cct due to intereference of IR LIGHT. How will I connect to obtain up down counting and know the presence of persons in a room. If possible send to me a circuit.

 

The catch is Up and Down counting. How do you plan on knowing whether their coming or going, not to mention the case where two people cross each other at the threshold.

 

could somebody help me!
I have apair of phototransistor and IrLED to enable me sense person entering and leaving a room. I would like to know occupancy by using updown counter fed by pulses from phototransistor cct due to intereference of IR LIGHT. How will I connect to obtain up down counting and know the presence of persons in a room. If possible send to me a circuit.

Will you use an ordinary counter IC or a microcontroller to count the people?

 

The only solution is to have two beams across the entrance, one in front of the other about 100mm apart, so that if say beam 1 is broken first then beam 2, that will give you the direction. otherwise its just counting on one beam.

 

thanks Digi Dave


to Mik3
Im using an ordinary up down counter i.e 4510 and
a D fliflop.CD4013

 

Is the choice of my ICs reasonable. I choose these because my supply is 12v. Otherwise advice.

will having the beams 100m apart bring about quadrature encoding?

 

Distance between beams will not determine quadrature encoding. Having two beams in one (and only one) mechanical path will make for quadrature encoding. IF you can get the humans to go through the path one at a time, or all in the same direction. Two humans in two directions at the same time will spoil it.