Laser Tripwire with 4 digit 7 seg Display for Counting People

Ok its not really Purple but the rest it accurate. The EYE is the LDR " Light Dependent Resistor" and it counts people.

Operation:

       A laser beam is directed across a doorway. The LDR is on the receiving end of the laser on the other side of the doorway.
When a person goes through the doorway and breaks the beam the counter is incremented by a count of 1.
Scene it counts the person coming and going, that's 2 counts for 1 person i just divide by 2 at the end of the day, or at anytime to get the true count of people.
It is not fool proof, sometimes it double counts. But sometimes 2 people go out at the same time and only counts as one. So i figure it averages out.

 Acknowledgements: 

    First and foremost this Instructable would not be without the help and coding expertise of  frollard .
He is amazingly quick and precise.
   There is a lot of knowledge here and they are willing to share that knowledge to help us learn.
Some of the people i have personally been involved with are:  iceng , He was the first one to follow my page. Him and steveastrouk were the first to help me through an electronics question. I was happily surprised when they both answered my questions clear to the very end of the discussion. Others include: maewert who has some 30 years of coding experience and it shows, ignoblegnome, Goodhart, pfred2 , Phil B. These are not in any particular order and if i have forgotten somebody i am sorry.

OK on with the build.

Step 1: Bread Boarding

  
The test circuit. It uses no resistors. How can that be? Well its compensated for in the code.
This is what SparkFun has to say about it, this is from the code:

This is an example of how to drive a 7 segment LED display from an ATmega
without the use of current limiting resistors. This technique is very common
but requires some knowledge of electronics - you do run the risk of dumping
too much current through the segments and burning out parts of the display.
If you use the stock code you should be ok, but be careful editing the
brightness values.
 
This code should work with all colors (red, blue, yellow, green) but the
brightness will vary from one color to the next because the forward voltage
drop of each color is different. This code was written and calibrated for the
red color.
 
This code will work with most Arduinos but you may want to re-route some of
the pins.
 
7 segments
4 digits
1 colon
=
12 pins required for full control

  

Comments

[iceng]

I like the fact that your ible is reliably authentic for a laser  trip wire of reasonable distance in feet.

Many previous trip wire ibles have been short distances ie a few centimeters.

Nice work :-)

A

[WWC]

While it can be rewarding to build something "FUN" or for fun.

I typically like to build something that can have some use to it.

Thanks

[maewert]

Ouch! That looks like it hurt!

[WWC]

That it did!
I am using a hot air gun to heat the glue, so it takes more fooling around with than an actual hot glue gun.