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### Topic: control a wheelchair  (Read 3419 times)previous topic - next topic

#### syrine

##### Mar 02, 2015, 02:28 pm
i work on a project with a whhelchair and arduino.i should start by commanding the wheelchair with my laptop.
so i used an arduino and i created a circuit
.
for my joystick a got 6 wires.
so when it turn left  the voltage of each wires is
white 3,9v
blue 1,1v
yellow 2,5
brown 2,5
to turn right
white 1,1v
blue 3,9v
yellow 2,5
brown 2,5

to go forward
white 2,5v
blue 2,5v
yellow 3,9v
brown 1,1v

to go backward
white 2,5v
blue 2,5v
yellow 1,1 v
brown 3,9 v

and the other to wires are ground and source.
so i created a circuit where i create  voltage divider with 2 resistor of 2,2 kohm and 2 resistors of 2,8 kohm .but it didn't work .i don't know where is the problem

#### AWOL

#1
##### Mar 02, 2015, 03:10 pm
I helped you by deleting one of your cross-posts, but left the one in the French section.
HTH.

#### keeper63

#2
##### Mar 02, 2015, 08:06 pm
for my joystick a got 6 wires.

and the other to wires are ground and source.
so i created a circuit where i create  voltage divider with 2 resistor of 2,2 kohm and 2 resistors of 2,8 kohm .but it didn't work .i don't know where is the problem

Without seeing a picture of the -bare- joystick (and even that might not help) - it is almost impossible to tell you what would work or how to get it to work. Heck, your experimentation may have killed the wheelchair controller - or your Arduino output pins; who knows...

At first - it sounded like the wheelchair joystick was simply a couple of potentiometers; some of the older chairs used these (btw - what make and model is the chair?); newer chairs tend to use inductive coil systems or hall-effect sensing joysticks (more reliable than potentiometers - which is a big thing when you are dealing with such a chair for a disabled person!).

But you mentioned two other wires for power and ground (8 wires?) - unless I am misunderstanding you (maybe due to the language barrier - though your english is better than my french!). Now - if it is truely only 6 wires (ie - four wires plus power and ground) - then that could mean something different. Again, information, pictures, etc of the chair and controller can be essential.

Wheelchair controllers are very finicky, for a very good reason; they basically refuse to work unless the input parameters (and other things) are perfectly in sync and specification; if anything is slightly "off" - the controller will refuse to do anything. This is meant as a safety feature, to prevent a chair from lurching off at high speed with a person in it, unable to control it. So - you may have had everything correct voltage-wise, but the controller found that the impedance of your circuit was off, or that the voltage was slightly wrong in some manner, or the signals weren't perfectly in sync, etc - and said "no way, no how" - and refused the commands.

Honestly - the easiest and best way to control wheelchair motors isn't with the wheelchair's controller (which is of a proprietary design that is nearly impossible to get information about how to interface with it) - but with a 3rd party high-current DC motor controller, such as one from Vantec or Roboteq - just be prepared to spend a boatload of cash - but they are heavy duty devices, and will work with a variety of input signals (both companies make controllers that can take servo input signals for control).

Lastly - be careful with testing your code on the wheelchair base; they are heavy and powerful things, and can seriously injure you if don't take good precautions. There was one individual in these forums who mentioned they had one go "runaway" and careen into a wall; had that been a person, serious injury could have resulted. So - test your code completely with the base up on a stand or something, before trying it out with the wheels on the ground - and always have some kind of kill switch setup on the system (an on-board kill switch and a remote kill-switch, combined together, are ideal).

I speak from experience on this; I work with a gentleman who has a non-profit doing repair and refurbishment of mobility chairs and scooters for donation. We also build remote-controller are robots, custom art chairs, and other such devices using a variety of parts (both from old mobility chairs we can't donate, or from other parts we scavenge or purchase). We've come to respect the power of the motors and weight of the chairs. So be careful.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

#### syrine

#3
##### Mar 03, 2015, 09:53 am
thank you for repling me .but i want to know if the circuit that i made is correct or no ?i don't realy know that much of electronics so i want some one to help me with it .thank you

#### zoomkat

#4
##### Mar 04, 2015, 04:52 pm
Why I like my 2005 Rio Yellow Honda S2000  https://www.youtube.com/watch?v=pWjMvrkUqX0

#### TomGeorge

#5
##### Mar 05, 2015, 01:53 pm
Hi,

Can you please post a copy of your sketch, using code tags?
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?

The joysticks put out a differential output for each axis, for the  reasons given by cr0sh.
What arduino are you using and why are you using a potential divider.

Tom......
Everything runs on smoke, let the smoke out, it stops running....

#### keeper63

#6
##### Mar 05, 2015, 07:45 pm
thank you for repling me .but i want to know if the circuit that i made is correct or no ?i don't realy know that much of electronics so i want some one to help me with it .thank you
I don't know.

I don't know what circuit you are using exactly (your description of it is vague), nor do I know what kind of joystick you are using (most commercial mobility wheelchairs do not use potentiometer-based joysticks, because of their tendency to wear out quickly, their noisiness, and their failure modes).

Until we know exactly what it is you are using for a circuit (ie - a schematic, or at least a picture of your circuit with things clearly labeled), and what controller/joystick/etc you are using - there's no real way to know if what you are doing will or should work properly.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

#### syrine

#7
##### Mar 06, 2015, 11:19 am
I don't know.

I don't know what circuit you are using exactly (your description of it is vague), nor do I know what kind of joystick you are using (most commercial mobility wheelchairs do not use potentiometer-based joysticks, because of their tendency to wear out quickly, their noisiness, and their failure modes).

Until we know exactly what it is you are using for a circuit (ie - a schematic, or at least a picture of your circuit with things clearly labeled), and what controller/joystick/etc you are using - there's no real way to know if what you are doing will or should work properly.
i'm using this joystick

i opened it and i found 6 wires  white blue yellow brown  red and black .
(red and black)=ground and source
the other like i discribe in the first post.
when i don't move the joystick thavalues are
white 2,5v
blue 2,5v
yellow 2,5 v
brown 2,5 v

can i send this value directly from the arduino 3,9v and 1;1v or i should creat a circuit like the voltage divider?

#### keeper63

#8
##### Mar 10, 2015, 07:53 pm
i'm using this joystick
Thank you - but unfortunately that wasn't as helpful as I thought it would be - I was hoping maybe somewhere in the literature at Invacare there would be something telling us what kind of joystick (resistive, hall-effect, or inductive) was being used. That does not appear to be the case, though.

i opened it and i found 6 wires  white blue yellow brown  red and black .
(red and black)=ground and source
the other like i discribe in the first post.
when i don't move the joystick thavalues are
white 2,5v
blue 2,5v
yellow 2,5 v
brown 2,5 v
You are making a few assumptions here. One, that red and black are for voltage (positive/negative/ground), and two, that the joystick uses potentiometers. Neither of these can be known for certainty until you have some specs on your joystick.

can i send this value directly from the arduino 3,9v and 1;1v or i should creat a circuit like the voltage divider?
Well - you could - if the joystick is actually a potentiometer-based joystick (in which case, I would expect the six wires to be connected as three for each potentiometer - rather than two for power/ground, and the other 2 pair for each potentiometer - but then again, who knows without the specs).

It's not going to be possible to figure out the joystick from anything Invacare will provide, so don't even bother with them.

If you can open up the controller, and remove the joystick module - then inspect it for any possible model number or manufacturer information (assuming it is marked with such - sometimes vendors of equipment like Invacare have their suppliers remove or not attach such information to the products they purchase) - that could be helpful in finding the specs for the part, to see what kind of joystick it is. It seems like you have already opened the unit - so can you provide pictures of the bare joystick device, plus any informational markings on it?

It may be that even that won't be enough, and to really find out how things are you will have to disassembled the joystick module itself (not an easy task, and it may be more trouble than it is worth). Like I said, the problem is you don't know what type of joystick it is, nor the pinout of it - without those two bits of information, you can't easily begin to interface to it.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

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