Counting up and down with a switch

[GeeTwo]

If you want a switch that counts both up and down, you really need something like a quadrature encoder, or a gray code encoder. Either of these has at least two separate switches. The simplest quadrature encoder is for rotation, and has one switch "on" for angles between 0 and 180 degrees, "off" for 180 to 360. The other switch is rotated 90 degrees, so it will be "on" for 90 to 270 degrees, and "off" for 270 through 0 to 90 degrees. With this sort of setup, you can tell which way the wheel is rotating based on which switch is "leading" the other towards each state. If the first switch "leads", rotation is in the positive direction, if the second switch "leads", rotation is in the negative direction.

I'll leave gray code for you to google.