Thread: rotary knob to keyboard encoder

get a BCD rotary endoder and use a comparator to determine which direction it is going. Then use a if this direction then send code xxxx, if othe rdirection send yyyy, else not moving so no code.

well what I see is you want something where you turn the knob to the left, it sends a 'L' key to the computer. If you turn it right, then it sends 'R' or something. That way you can control it.

So if you get a BCD knob it will send out a binary value depending on where it is.

Have some clock at a relatively slow speed like 10Hz or maybe 15Hz where it saves the current value to a memory block, and then use a 3 value comparitor to compare the BCD in memory to the one currently on the knob. If the current position is greater than the previous value, then it is being turned clockwise. If the value is less, then counterclockwise. If no change, then not moving.

This is all hardware end.

Now use the left/right/no_movement output of the comparator to a keyboard circuit to send whatever key you want on each of those values.

I find them at local electronics junk stores. Usually about $1 to $3 for a cheap one.

Here are really cheap parts from the early 80's if not before. Meaning really cheap. THey still work.

Nowadays they use PIC's. After TTL, there was CMOS, and now there are fully programmable chips.

74LS page: http://www.unicornelectronics.com/IC/74LS.html

74LS682 (An 8bit comparator): http://www.unicornelectronics.com/ft...84-685-688.pdf

Truth table is on page 2 of the pdf.

One of the comparator chips is $1.50 just to let you know.

LS just means a a low power version.

TTL runs off of 5v, and CMOS uses 3.3v.