Person Counter

[colin mac]

I want to make this project which increments and decrements person that enters room.
I don't know much about microcontrollers but I'm wondering how to control 4 7-segment displays with the seven wires?

 

[ThermalRunaway]

The 7-segment displays in that circuit are actually controlled by eleven wires. 7 are used to light up the required segments, and 4 are used to select each display. The Microcontroller will switch through each of these displays in turn, outputting the required digit via the 7 data lines. It does this so quickly, that your eyes see the entire display lit up at the same time.

There'll be a display function within the software for the Microcontroller which controls the multiplexing and update of the displays.

Brian

 

[ThermalRunaway]

If you build the circuit (have you got the software and the ability to program the micro?) and you get it working, look at the display and then chew something crunchy like... ummm... a packet of crisps or something. You'll see the display dance around a little as the MicroController switches through the displays. Or, alternatively, try looking at it with a video camera. Depending on the refresh rate of your video camera (try changing the settings) you should be able to see the displays multiplexing.

Brian

 

[colin mac]

Oh, one at a time, I see now, thanks a lot. I have the program for it, but it won't be for another while few weeks until I get to make it.

 

[Gayan Soyza]

Oh, one at a time, I see now, thanks a lot. I have the program for it, but it won't be for another while few weeks until I get to make it.

You got the point! the segments are turning on one at a time if this done in a very speedy you will see all the digits displaying at once.

The above circuit is from Binu Ji’s website.

Note that the two LDR’s must be mounted on the correct place. You will notice where to mount after building this circuit.

Secret of this circuit!

If the first LDR sense first light or dark it starts to increment the digits.
If the second LDR sense first light or dark it starts to decrement the digits.

 

[colin mac]

The person must pass one at a time and not cover both at any time I take it?

 

[Gordz]

Make the entrance narrow to force single-file and ensure the sensors are far enough appart so they cannot both be blocked.