First attempt at a RC bot, PLEASE help! :-)

[ROBOT420]

Hello, I am glad to have finally found this forum! I am doing your basic remote controlled power wheelchair base, and I was wanting to make sure how to go about keeping the speed control as well as the charger plug. I have a Jazzy powerchair, a Sabertooth 60a motor controller, and a transmitter and receiver. Any tips or advice that will save me some head scratching would be greatly appreciated! Thanks, Steve

[jlizotte]

Steve,

I just finished interfacing to a working wheelchair, but I kept the wheelchair electronics.

Am I correct in assuming (since you mention the Sabertooth) that you're bypassing or removing the onboard wheelchair controller? If so, what do you mean by keeping the speed control?

Am I also correct that you plan on using your wheelchair motors at 24v, and that's why you want to keep the charger wiring?

John

PS. two VERY IMPORTANT TIPS (from experience) : 1. ALWAYS test your chair up on blocks, wheels off the floor. If your controller or your code screws up, wheelchair motors are very powerful. You can get injured or some serious damage can be done to your workshop/testing area. Put it on blocks every time you change code or hardware, and test it there first. And 2. Install a kill switch somewhere on the top of it. In case it comes off the blocks, or say, gets interference from the remote while using it, you or those around you need a quick way to kill the power to the motors. A big red switch (illuminated if possible) is the most intuitive solution for this.

[ROBOT420]

Thanks John! Two great points, shopping for a big red button now!
 I do plan on using the chair batteries as they have been replaced recently.
I am using the Sabertooth for ease of use in wiring up my receiver, once I have this one under my belt I will try other ways no doubt.

[jlizotte]

What model Jazzy is it?  Do a google search for "Jazzy xxxxxx service manual". You can find most of them online, and many of them will give you the pinouts for the connectors like the charging port, etc.

Also, don't forget (if you're using the Sabertooth), wheelchair motors have electronic brakes in them that must be released before energizing the motor circuit. The wheelchair controller usually handles this. I mention it because if you wish to use the brakes, you'll have to control them before and after you energize the motor. If you're not using the brakes, you can remove them from the rear of the motors. Either way, you need to be aware that they are there. The motor won't spin until you release the brakes. The brakes are engaged by default, and must be energized before they release.

[ROBOT420]

Great point! Thanks again, the Sabertooth has regenerative breaking and reverse (so it charges the battery's when you stop somehow?) I will see about the breaks though.
The "speed control" that is on the stock controller lets you adjust the speed at full stick. If I just use the Sabertooth will it only supply what the motor(s) need(s)? I want full speed (such as it is) but I do not want to melt anything. Thanks again, anything else you can think of?

[jlizotte]

Nothing more until you get further into what you want to do, or get started.

If you're using the Sabertooth, you'll control your speed through software (somewhere). lol. The Sabertooth will work just fine...it will basically switch the power coming from your batteries into your motors. I'm not sure how it handles speed control. You'll have to look that up. I put a microcontroller into the joystick of my chair, and by varying the voltage I can change my speed. Other more experienced forum members can help you on the Sabertooth side of things.

You'll have to choose between using the Sabertooth and the stock electronics on the chair. I'm afraid it's an all or nothing choice when it comes to controlling the chair. Both have advantages and disadvantages. If you're planning remote control and already have the Sabertooth, that's the best/easiest way to go. How you deal with your brakes is going to be a choice you make.

If you think you might want to play with the stock chair electronics later, just remove them or disconnect them after taking pictures or making a drawing of the connections. Remove them without damaging them, and you can reuse them later. Or if you don't want them, sell them on Ebay to help finance your project.

[ROBOT420]

If you can walk me through how to do it with the stock controller then I would be fine with that and will just use the Sabertooth on something else. I don't know enough about it to know WHAT choices I have. Thanks again!

[jlizotte]

Using the chair's controller is a lot more work, and a lot touchier, due to all the safety features built in for the wheelchair user. At a minimum, you'd have to use a microcontroller hacked into your joystick for proportional speed control, or on some controllers, there's an external 9pin connector you can use for simple on/off in each direction, but no speed control. But a simple variation in any of 3 simultaneous voltages can throw the chair into error mode and stop it dead.

Since you already have it, I'd really recommend starting with your Sabertooth, while leaving the original electronics untouched. Then re-use them later when you get bored, or sell them. You'll have better motor control from the Sabertooth, too.

[ROBOT420]

Sounds good. What was the verdict on speed with the sabertooth? will it have them at wide open (would be fine)? I guess I need to ask....How does the chair controller vary the speed? Is it PWM or voltage, orrrr? Thanks again

[jlizotte]

Somebody else here will have to answer for the Sabertooth speed control. I've not worked with them. I like what I read about them, and they get great reviews, plus they feature an RC mode, so you should have no problems there. Hopefully someone here can chime in on how the speed control for them works.

As for the chair controller...it depends on your chair. I hacked into my joystick. At neutral, it throws 2.5 volts on both axis wires. I measured full forward, left, right, and reverse, and voltage was up as high as 4V and as low as .7V depending on position. I send the voltage I need across 2 wires depending on what direction and speed I want to go. One problem with this is that I need 2 wires at 2.5V for chair-neutral. If I shut off my controller card BEFORE I shut off the motors on the chair, the voltage drops to 0V and the chair starts to move. (See why I mentioned a kill switch? LOL). Some joysticks use 5 volts like mine. Some use 12. Some use 24.  Just make good friends with your multimeter.
 
Internally, wheelchair controllers have their own network protocol. Rnet is just one of them. Others use single wire serial communication, or just SP1 internally. It's a confusing mess, and most wheelchair manufactures don't play nice when it comes to sharing technical information.

Seriously though, if you just want to have fun, use the Sabertooth. Bypass the chair electronics completely. It will be much easier, and the speed control shouldn't be an issue. I just don't know how it's done on the RC circuit, but I'm sure someone here can help you with that. What took me a couple weeks of research to learn, and a couple of days to implement and test using the wheelchair controller, you can accomplish in a couple of hours by using the Sabertooth.

Good luck! And keep us posted!

[ROBOT420]

Well here goes nothin'! About to (gently) dismantle this chair ad see what secrets it wants to share with me. If possible I plan to do it WITHOUT shocking the piss out of myself somehow! I seem to have a real knack for doing that :-(  .... I will post pics later.....

[ROBOT420]

Hey on my jazzy the stock motor controller seems to also have the battery charger built in to it. Anyway to separate the two or do I need to design a new charging system? Thanks, Steve

[jlizotte]

You've got to be more specific, Steve. Do you mean the plug is on the joystick housing? Do you mean you plug the controller into a normal wall socket? Do you have a seperate charger that you plug into the chair somewhere, then into the wall? (Pics might help)

[Tommy]

seems to also have the battery charger built in

the stock jazzy on-board 7Amp charger is separate from the motor controller and can
be used without the stock joystick controller, just got to keep it wired to the batteries.

I believe it's worth the bs of using the stock joystick controller because of all the safety's
built into it. if anything goes wrong it goes into a fault(very handy).
wont let you burn it up, or start up without the joystick centered(Sweet!)


for last three years I'v been using the stock motor controller in my project, but I'm testing
the sabertooth 2x60 right now to see if it can be used if my current motor drive ever fails.
but I had to add a micro to the system to mimic the safety features of the stock controller.

best to keep the brakes if possible, your going to need them.

Tommy     

[jlizotte]

Thanks for jumping in, Tommy. Your Mule was a big inspiration to me 

I'm curious though, what software did you use to get the dashboard that shows in one of your videos? Pm me if you don't mind. I don't want to hijack Steve's thread.

Thanks.

John

[ROBOT420]

Hijack away! I will take all the related info I can get! :-) Well I have the breaks off, and the whole chair stripped sown to the frame/battery tray. I am now starting to sand it some and spray it with Purple metal flake paint from Roth. At least this way, even if it NEVER works, it will still LOOK cool! lol!

[jlizotte]

lol. We're going to want pictures

[ROBOT420]

I now have both motors under remote control!

Why is it so hard to even add ONE pic on here? I got my Avitar changed to my new Ohm/Watts law tat (just in time for finals! ) jut no dice posting pics to the forum. What am I doing wrong? Thanks, Steve

[jlizotte]

Great job on the motor control!! 

When I post pics, I host them on my own website then put the url between the "img" tags. I think you have to host your pictures elsewhere, like photobucket, your own website, etc etc then just use the link here.

[ROBOT420]

Thanks! I will try to get some pictures of the project up soon.

[ROBOT420]

Here is my project, and a video of how the paint turned out. looks crappy in the video but it came out real decent.

http://s1362.photobucket.com/user/420photo420/media/20130327_190829_zps55588f8b.mp4.html?sort=3&o=1

http://s1362.photobucket.com/user/420photo420/media/20130405_140416_zps02c15b01.mp4.html?sort=3&o=3

[ROBOT420]

More project pics...

http://s1362.photobucket.com/user/420photo420/media/20130326_145746_zps366e62f7.jpg.html?sort=3&o=12

http://s1362.photobucket.com/user/420photo420/media/20130412_153629_zps50ba4641.jpg.html?sort=3&o=9

http://s1362.photobucket.com/user/420photo420/media/20130324_201233_zps5375c004.jpg.html?sort=3&o=5

http://s1362.photobucket.com/user/420photo420/media/20130404_155442_zpsbeb23cbf.jpg.html?sort=3&o=7

http://s1362.photobucket.com/user/420photo420/media/20130404_161054_zpsea2c0cdd.jpg.html?sort=3&o=8

http://s1362.photobucket.com/user/420photo420/media/20130405_123536_zpsa1c1c81c.jpg.html?sort=3&o=10

http://s1362.photobucket.com/user/420photo420/media/20130324_202202_zps97435923.jpg.html?sort=3&o=4

http://s1362.photobucket.com/user/420photo420/media/20130323_115245_zps9144120c.jpg.html?sort=3&o=0

Now for final assembly! :-)

[ROBOT420]

Phase one complete!

http://s1362.photobucket.com/user/420photo420/media/20130429_123146_zpsae19c0c5.mp4.html

[Duane Degn]

Wow! That thing is cool!

It looks like that has lots of power to spare.

So what's phase two?

[jlizotte]

Dude...that looks awesome! You should be proud. Really cool 

[ROBOT420]

Thanks guys! You should see the 5 coats of Purple flake and 3 coats of clear in the direct sunlight! Phase two is going to include me putting a third (accessory) battery on that rack I welded on the back. This will make it ride wheelies further (I have wheelie bars planned out in case I need them), as well as power the duel horns, LED's, these little speakers I have with a voice module that records and plays back 10 seconds of sound, and if I have time (only 4 weeks left until final presentation for school) I might mount this robotic claw I have one there but with a small water cannon on it (not too sure about the whole water and electronics thing though)...and then.....TRY TO TAKE OVER THE WORLD! MUUUHAHAHAHA ! Or, get an A on my final project...either one will due.

[ROBOT420]

Thanks John! Two great points, shopping for a big red button now!
 I do plan on using the chair batteries as they have been replaced recently.
I am using the Sabertooth for ease of use in wiring up my receiver, once I have this one under my belt I will try other ways no doubt.

SO, first of all I would like to second the motion on the whole "test it up on blocks" thing. My dumb ass thought it was neat that the programmable transmitter allowed me to drive the motors ABOVE 100%, so I set it on 110% and just figured that I would just BARELY move the stick. What I failed to realize is that these motors are WAY restricted by the factory motor controller, so when I bypassed that with the Sabertooth it was about 3 times faster then stock even before I set it to 110%! To make things worse, I crossed 2 signal wires during final assembly making left and right into up and down and vice versa. Long story short, unless you want your robot to damn near run your cat over, and then almost tear your own leg off, on the way to smashing a dent in the wall, then use the blocks!

Also, any clue where one might get a big red emergency shutoff button that will not melt with 30A-60A running through it?

[jlizotte]

lmao. I'm not too worried about my wife's cats....I was worried about my old dog who doesn't move as fast as she used to.

I'm still looking for a BIG RED BUTTON, too. I can kill my motors by grounding one wire (thanks to the stock controller). I've got a small toggle switch on it now, and showed the wife where it is, but I'd still like to get something more intuitive.  Let me know if you finally find one.

And yep. I read about using blocks here, and started out that way, but I'll be honest...my first few tests off the blocks resulted in the chair trying to climb my leg and also pushing my workbench around. lol. I got lucky. Only a few bruises and a chance to sweep the dirt out from under my bench before I pushed it back into place. lol

John

PS I really like how you "tricked it out". The lights, etc. Your bot looks cool. Really nice job.

[ROBOT420]

Thanks J. I will keep ya posted on the off button, right now I just use two "quick connect" plugs to open the motor circuit via the ground wire to the sabertooth. I will post an update when I get more bells and whistles going. Steve

P.S. My department chair ruled that the Ohms/Watts law tattoo that is pictured on my avitar DOES NOT count as cheating! :-)

[ROBOT420]

Wow! That thing is cool!

It looks like that has lots of power to spare.

So what's phase two?

Thanks!
LOTS of power to spare!