alehander,
You said that you had a PLC (Programmable Logic Controller). If you have a PLC, then for God's sake, man, set up your timer as an INTERNAL timer in the PLC. That is one function that PLC's do very well. Now, if your problem is that you need to be able to change the Timer Preset Value from outside the PLC program (the number it is timing up to), then there are serveral input methods. The simplest, cheapest way to input a number is probably with a BCD-coded thumbwheel switch. I am looking at a 10-position BCD switch in the Newark Electronics catalog for $12 dollars US. You can buy thumbwheel switches with 1, 2, 3, 4, or more digits. Each advance of the thumbwheel moves the switch 1 number up. The output, however, will be a binary-coded decimal number sent as a group of 1 or 0 inputs to your PLC. To have a range 0 - 32, you need 5 inputs. Six inputs will give you 0 - 64, and so on. Then inside your PLC logic, you set up rungs to translate the input back to a decimal number (or Octal if your PLC requires that). Then MOVE this number into your internal PLC timer Preset Value. That's it, you are done!