"Tempest 2000" (Jaguar) Optical Encoder Problem

RARusk · July 30, 2009

This is a side topic to this one I started when I was completing this project.

Although this construct works great, there are imperfections that I am trying to work out. Basically, I am trying to create an optical encoder to standard encoder "translator" to remove the imperfections.

There are two parts to this possible solution:

The first part is what I call a "motion controlled gate". When you stop spinning an optical encoder the two lines coming from it can be in one of four states:

1 - on/on

2 - on/off

3 - off/on

4 - off/off

Because of the special way the encoder needs to be hooked up to the Jaguar joypad in order for it to work this can cause problems. Especially with the camera angles.

One thing to do is to run both lines through something that will shut off both lines when the paddle is stopped regardless of the state of the lines going into it. This would represent the indents that the metal contacts would settle into when using a standard encoder.

I recently asked Intersil for help on this subject and one of their techs gave me this answer:

"For the first issue, it looks like you need an ON-OFF-ON type switch, Left is on, center is off/open and right is on. I think you can do this with two CMOS SPDTs."

I don't know which ones are the best for this application or how to hook them up to get them to work in this fashion. Maybe someone here can point me in the right direction. Considering that I was using some of Intersil's limited resources when I asked them about this problem I didn't want to ask more than I should.

The second part to this translator is a little bit easier.

After running the lines through the "motion controlled gate" then the lines would go to a high speed switching device similar to the one below:

To make this work with the Jag the column for both the right and left directions (on the joypad) would be attached to NO1 and NO2, the row for the left direction (on the joypad) would be connected to COM2, the row for the right direction (on the joypad) would be connected to COM1, the left signal from the optical encoder (after going through the gate) would be connected to IN2, the right signal from the optical encoder (after going through the gate) would be connected to IN1, and, of course, the necessary voltage and ground lines.

This would represent the three poles that you would attach the left row, right row, and the left/right column on a standard encoder.

The tech from Intersil thought my suggestion on using this particular chip was solid so I believe I am on the right track.

But I would like to try to find a chip similar to this one but in a socket version (for easier prototyping) or better still, a chip that has both of the features I am looking for.

If I can solve this problem for my construct and remove the imperfections then I may try to make a second version of this device but with a SlikStik and put it in some sort of arcade quality case.