Re: Commodore joystick ports

From: john/lori (
Date: 2007-04-21 13:39:29

Daniel O'Shea wrote:

> I apologise, I wasn't intending to open up such a can of worms! As I 
> stated in my original post, I have a variable voltage of 0 to 5V (no 
> microcontroller involved) that I want to translate in to a variable 
> current using a transistor. And so, I am lead back to my original 
> question - what kind of transistor and what value would work best to 
> provide a variable current which duplicates the potentiometer's variable 
> current? and do I need any extra components besides just a transistor? 
> thanks!
>       Message was sent through the cbm-hackers mailing list

After thinking about it a bit, here's what I came up with.
I'm not optimistic about it's behavior, (non linearities and
I didn't go so far as to breadboard it or even simulate it,
it's just some doodling.
No doubt it would have to be tweaked.
I was figuring for 2N3906, 2N3904 but I doubt it's critical
(any roughly similar transistors would probably do).
Note there's an inversion, a higher voltage in would
give a lower reading.

             |         |
            3.8K      390 ohms
             |         |
             |    +----+
             |    V    |
0-5V        |  |/pnp  |
  IN o--13K--+--|      |
             |  |\   |/npn
             |    +--|
             |       |\
             |         V
            18K        +---o POT
            /// gnd


       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail pre-2.1.8.