Load Cell Joystick

[LegTaste]

Wondered if anyone had made their own force sensing joystick, i know there is a couple of cougar mods out there, but i'm after a DIY solution.

 

Finding force sensors of any sort isn't so easy, and they wont be cheap.

 

Load cells as pictured below can be had for more reasonable prices

 

 

I was almost set but then i realised a problem, although people have used these to great effect for car brakes, they will start at zero when off the brakes, while with a single joystick axis you will start with a centred pot and have movement in each directions.

 

I have two ideas, one is to somehow apply half the amount of force/weight to the load cell while the stick is centred with one direction applying more force and the other easing up.

 

The other is to use two per axis, but i have no idea if this is possible or how it will be done. I intend to use one of those leo bodnar circuits, but if anyone knows of anything else that will do what i require i would consider it.

Edited May 11, 2010 by LegTaste

[Alex_rcpilot]

It'd be difficult to separate X Y and twist inputs with load cells. I hope the following pictures of the X65F will give you some more ideas.

 

 

I got these pictures from 3GO*CHN-388.

 

If it's possible for you to obtain load cells, you might as well have access to strain gauges. Try to search for different configurations with strain gauges, there are various circuits designed for X/Y bending and twisting measurements. Good luck.

[LegTaste]

Thanks for the info. Any idea if the shaft is solid or hollow?

 

For anyone else that maybe be interested here are some nicely priced strain gauges, cheaper than a good quality pot.

 

http://www.rapidonline.com/Electronic-Components/Sensors/Strain-Gauges/Strain-gauges/30178

[CyBerkut]

Leo Bodnar has load cell amplifier configurations available for both uni-directional (pedal) and bi-directional (joystick)

 

http://www.leobodnar.com/products/LC-amp/

 

I don't know if his USB Load Cell Interface BU0836-LC can accomodate both types of configs:

 

http://www.leobodnar.com/products/BU0836-LC/

 

Good luck!

[Alex_rcpilot]

At least Leo's board handles USB pretty well. If LegTaste has decided to use load cells or strain gauges, I think he'd also be interested in learning some skills with building analog circuitry. It only takes some differential amplifiers, resistor network and capacitors to convert physical inputs into 0~5V linear signal. Enjoy the process:)

[LegTaste]

Didn't start thinking about load cell/force sensing joysticks until after i placed my order for a BU0836. That was a week ago actually, had no response to my emails but i gather this has happened to a few people. I don't fancy over paying another £5 postage for such a tiny item considering i live in the UK, and waiting so long for it to arrive.

 

 

http://www.hux.net.au/?tag=load-cell-interface

 

 

This looks very similar although not bi-directional, anyone know what modifications this would require?

 

 

Edit

 

Posted this before reading your post alex, i've built many circuits, but i cant say i have much of an understating of the theory behind them, converting a schematic to a layout is as in depth as it gets for me.

Edited May 11, 2010 by LegTaste

[Alex_rcpilot]

I'd be happy to convert sch into PCB layout for you. I wish I could design the sch for you as well, but I can't make that promise coz I've been multitasking for myself since the beginning of this year. :cry:

 

You might wanna start with these strain gauge diagrams:

 

 

I still haven't checked them thoroughly, but I think one of these examples will fit your needs. Once you've chosen the right configuration, I may find you some un-tested application circuits for you to test with breadboards. Can't test them for myself because I have neither the shaft nor the gauges with me.

[LegTaste]

I was just looking at some of the different configurations although not quite as indepth as the examples you have supplied.

 

Thanks.

[aparkfind]

Great technique works behind the working of load cells .This page really helpful for those who want to had some information about load cells how it works.IF i am not wrong it's about double ended load cell which are commonly used in these days .

Edited June 27, 2014 by aparkfind