Rotary encoder / Wheel encoder

Wheel speed
==========
Why ?
-----
Convert a binary information in a speed and with direction knowledged

### Requirement
1 GPIO (Raspberry pi)
2 endstop sensors
1 spring
3 nails
6 screws (2 by endstop and 2 for spring)

### Print parts
**Wheel**
Diameter : 50mm
4 holes so 4 states 0 and 4 states 1 for a complet revolution

** Main part **
To fix spring, wheel and sensors

** Holder **
To fix main part and spring

### What we want to get on the raspberry GPIO
number of change of state 0 -> 1 -> 0 -> 1 ... by rotation : 8

### Config
You can change settings:
- pin numbers used by 2 endstop sensors (23 & 24 by default)
- wheel diameter (5cm by default)
- number of holes in wheel (4 by default)

### Code part
Create a file "nb_turn_second.py"
Add permissions (chmod +x nb_turn_second.py"
Insert this script inside and run it with "./nb_turn_second.py"

```
#!/usr/bin/python

import RPi.GPIO as GPIO
import time

print "starting..."

pin_id = 23