Thumb joystick insteand of a rotation pot

[jaydskate]

Hi, I would like to change my rotating pot by a thumb joystick on my zoom controller.
The main problem is that the ones I got are 10k (8.32 k to be precise) instead of 20k. How would I go about modifying it to get a 0 to 20k range.
here's a picture of the unit.

Thanks in advance

Jay

 

[Pickthorne]

To avoid having to build additional circuitry, perhaps you could swap out the trim pot for a 20k. To my eyes it looks like this thing uses an off-the-shelf component, and I bet if you go to your local electronics supply you might find one that can be made to fit.

Just curious, are you using both axis, or just the one?

Craig

 

[Paul F]

Call the company you purchased the joystick from and find out who the manufacturer is of the pot. Then go buy the 20k version. I took mine apart and I see that the pot actually snaps into the metal housing. It isn't any ordinary trim pot. There are no marks on it to identify the manufacturer.

You may not like that joystick. I used that one on a jib pan/tilt head. While there is nothing wrong with it as such, there just isn't enough leverage to get proper control. It might work ok for a zoom control, but I didn't like it for my application. I switched to this: http://www.servocity.com/html/2_function_joystick.html, which is probably not what you need for a zoom control.

[edit] - keep in mind that the wipe action of the joystick is limited and doesn't use the full pot range, so the actual pot value you need will be different than the range the joystick is giving you.

 

[Richard Crowley]

If it is used as a true "potentiometer" (an adjustable voltage divider), then the precise value of the pot is not very critical. I would think that 99% of all controllers like that use a true potentiometer circuit. It is the VOLTAGE coming out of the center-tap wiper (which is proportionate to the input voltage and the physical position) that is the operative concern here, not the absolute RESISTANCE value of the pot.

The only significant downside of using 10K vs. 20K is a slightly higher current. But that should be of no consequence unless you are talking about battery life in a very low-power circuit (no camcorders qualify in that category).

There is probably no harm in trying your 10K device. Since you didn't actually identify your zoom controller, it is not possible to offer any better response.

You might want to confirm that your joystick puts out the same voltage range as the original pot. The joystick is limited to ~ 90 degrees of rotation which is only 1/3 the travel of a typical pot.

Yes, those pots on the sides of the joystick are rather conventional, but finding a mechancally-compatible replacement pot of a different value is highly unlikely. Fortunately, it is not really important.

I was planning on doing something similar where the side-to-side motion would have the same effect as a conventional zoom control, but the forward-back would have a "multiplying" function for speed. So that if you "pull" the joystick back the full side-to-side travel would have a very low speed, while "pushing" the knob forward would make the side--to-side motion much faster. It would combine the functions of the zoom rocker, with the "zoom speed" control found on many controllers. Having never seen anyone else suggest such a scheme, I hereby claim it as my own original idea.