Using the AX500 with potentiometer Joystick

Hi,

I have built a two axis remote head for a camera. Here it is

The motors run on 12v and draw about 3A each, and I would like to use a Roboteq AX500 controller to run it using a potentiometer joystick. This joystick has two standard 5k pots, but the only problem is that the lever only moves 40 deggrees (thats 20 either side of centre) so only a small ammount of the wiper is used. Im worried that this limited movment of the wiper will mean that I will not be able to get full control of the motors using this joystick... I have spoken to the joystick people and unfortunatly I cannot take the 5K pots out and replace them with that of a differnt value.


Apem Series 5000 joystick, click for datasheet

Is there a way to trim the range of sensitivity using Roborun or soldering fixed value resisters into the circuit?

I also assume I can use two potentiometers, one for each motor, as this is unclear in the AX500 manual.

Thanks very much for any help,

Pete.

There is no way in the current version of the firmware to make the controller give the full speed range with only 40% of the pot movement.

We have a beta version of the firmware that lets you do that by entering the min, max and center voltage using the PC utility, but it has not been fully tested and is not guaranteed to be bug free. You may download it from <A href="dev.roboteq.com/dev1/files/software/beta...p20u-042606-elco.zip" target=_blank>www.roboteq.com/files/software/beta/roboup20u-042606-elco.zip

You can not use resistors to widen the range of the potentiometer. You can use resistor to make the range more narrow.

Hi,

The track of the potentiometers is 220deggrees so the movment is more like 20 percent. I assume that using this beta application, It will work ok anyway?

When is the beta likely to be complete and bug free? If there were any bugs would it just affect the programing, or the operation of the board once it has been programmed?

Thanks,

Pete.

You will be able to set the voltage for the min and max. It should work with 20% range as well, but this is for you to verify.

This feature was developped a year ago but never made it to the final release. It may or may not make it in the final version based on customer demand. If it does, it would be sometime next year.

Mm so its quite a risk for me then, if it works then thats fine, but if it dosnt then I am knackered..

How would I use this firmware, would I install it on the board then use roborun to set the parameters?

Thanks.

If it doesnt work, you can always reinstall the original version. It is in your My Documents folder.

Use Roborun to install. After installation, use Roborun to set the operating mode and min/max voltages.

Yeah, but my point is that if it dosnt work, i will have spent £126 and £35 on a control board and joystick that are both totaly useless to me...

What are the chances of it not working?

It should work.

But if it doesnt, then your options are:

- Power the board with 24V. This way, at 20% power, you will get roughly the same speed than 40% at 12V

- Get a joystick that give full pot travel. Penny &amp; Gills makes a few models. Ckeck the 3rd party vendors link on our web site.

- Add an external amplifier circuitry that will amplify the pot's output swing to the full 0 to 5V. This is a bit more complicated but if you wish to poursue this path, we can make a few suggestions on how the circuit would look like.

Oh good, well Im glad its not all over in that case.

I will have a look at the Penny & Giles units, can you recomend any?

Il buy the board in the morning then, might as well.

Thanks.

Here is an example of a joystick that would work well <A href="www.pennyandgiles.com/docGallery/106.PDF" target=_blank>www.pennyandgiles.com/docGallery/106.PDF

Any pot value above 1K is fine. Go with the one that delivers the full pot swing (0 to 100%)