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Author Topic: Wheelchair Motor Controller. DX bus protocol  (Read 2571 times)
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Hi Group
I just got an old wheelchair with some brutal motors. The electronics seems to work fine and my plan is to use it as a base for a Lawn Mower. With 1300+ Square meters of lawn and a broken Murray garden tractor I need a replacement made before spring.
The base is just about perfect for this usage.
The Motor Controller is controlled via a DX-bus whatever that might be.
I have not been able to get any specs on it yet.

http://www.dynamiccontrols.com/health-professionals/products/dx shows a diagram of the wheelchair.

Has anyone here tried to hack into this DX Bus?

Regards

Peter


Peter
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Have you tried to contact the company? - http://www.dynamiccontrols.com/health-professionals/talk-to-us -
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Rob Tillaart

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I won't post the whole thing here - but I want to reiterate my warning to you, as I do to others, to think of safety first in the design, control, and coding of such a machine. You do not want this to be a runaway machine, especially when testing it. Do a search on my name to help you find my posts on advice I have given others who have pursued similar machines...
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@cr0sh
Definitely right, a (serious) warning is in its place.

BTW old posts can reverse chonologically be found in your profile
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Rob Tillaart

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I would be nervous about this also but I'm working on a lawnmower also. Small 12 Volt motors and not as beefy as wheelchair motors. My design is similar to the retail version. I like to try and build it myself...thats the fun.
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I would be nervous about this also but I'm working on a lawnmower also. Small 12 Volt motors and not as beefy as wheelchair motors. My design is similar to the retail version. I like to try and build it myself...thats the fun.

I've got a Friendly Robotic RL500 waiting for me to get working on - found it on Craigslist for $50.00...

smiley
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Out of curiosity, what kind of motors do you plan to use for the blade?
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Blade Motors
I am not sure yet. I was thinking of using a Picaxe (I have plenty lying around) to controll the speed of a cordless drill motor. Then depending of the load sending a signal back to the arduino (or errror codes) so the Arduino could adjust the speed of the mower accordingly to what the rotor motors can handle. I think Im aiming for 3 30 cm diameter rotors (Perhaps 4) so the width of the cutting table should be around a meter.

For a perimeterwire i have not figured out what to do. I would like to make devide the lawn into segments that could cut in a different way. Perhaps i chould use a actuator to adjust the hight of the cutting table? In this way i could make a putting ground with really short grass and perhaps cut it on a daily basis. The rest could be ewery third day.

Any input on the blade/motor design would be highly appreciated.

Peter
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This interest me because I am also working with a lawn mover project. I have already bought two 250W/24V dc motors for the differential drive and built a h-bridge + PS2 wireless controller interface for it, but I haven't yet figured out how to spin the blade. I originally planned to buy a third 250W dc motor, but I'm now sure if it is powerful enough to actually cut the grass. On the other hand, if I get more powerful motor, the I get less mowing time before I need to recharge the batteries.
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I would be nervous about this also but I'm working on a lawnmower also. Small 12 Volt motors and not as beefy as wheelchair motors. My design is similar to the retail version. I like to try and build it myself...thats the fun.

Want a "sure to sell" idea? I'll give it to you anyhow...

Note the number of "cookie-cutter" homes (well, at least here in the States; not sure about other places) where the "front lawn" is a patch of grass the size of a postage stamp. Ok - that's an exaggeration, but not by much.

Anyhow - I've been in these kinds of subdivisions, and have watched the proud homeowner trot out a large mower, start it up, make three swipes, and call it done. Lots of work for little payout, plus the noise, and perhaps the pollution given that an electric seems to be rarely used, and the engine only runs for a minute, if that.

In short - if you could build a robotic mower somewhat the size of a Roomba, that could just be pulled off a charger, sat on the grass, turned on and let go - you could probably have a very marketable product.

Now - I've noted that I have a Friendly Robotics RL500 - this is not what I am talking about; that's a robotic mower designed to cut a much larger lawn. The mower itself is about the size of a regular lawnmower, and uses a couple spinning blades (and is anything but lightweight). It is much larger than what is needed for these small lawns that are fairly commonplace, it seems.

I think, though, that something the size of a Roomba that could handle such a micro-lawn would be a good selling product. Especially if it didn't require a buried signal perimeter wire or anything else to detect the edges. It just needs to be something that can taken out of the box, charged, plopped down and run. Making it somewhat "finger safe" would also be a nice thing, if possible.

Now - for you are any others building a robotic lawnmower - there's a few things to check out that might be worthwhile:

1. Take a look at past designs - particularly the Friendly Robotics RL500; it's a fairly simple, but robust design. Another design to look at is the "MowBot" from the late 1960s. Specifically, there's an Popular Science article in the January 1969 issue (see Google Books) about this mower. Really, it was a precursor of the RL500, and anticipated most of the technology.

2. Check out the radio controlled mower that was featured in Make Magazine not too long back; r/c mowers have a long history, too. Something to keep in mind, is that for large areas to cut, using a gas-powered cutting deck makes great sense, giving you longer run-times and concentrating the battery toward powering the wheels. You might also be able to rig something in a "hybrid" manner, using the engine to drive the blade as well as a generator to power the motors (maybe with a small battery in parallel). Don't discount an engine just because it is noisy and a bit messy.

3. What about the concept of a robotic reel mower...?

4. Rather than a perimeter wire (which needs power, can break, etc) - what about buried magnets sensed by a hall-effect sensor?

Just a few ideas... smiley
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Ok, I have to add what I'm doing but I'm sure not the best.

My lawnmower will be autonomous using sonar, IR and some other sensors to detect the change from pavement to grass. Tried a color sensor but didn't work well.
I have encoders on the wheels for distance, GPS and compass.
Xbee to transmit to my computer and a LCD screen.
Pan/tilt for WR1 Sonar sensor. Scans back and fourth as it moves so it can search for a path if necessary.
Three 12 volt motors for the blades.
Two 12 volt batteries 5 AMP for drive motors and blades ( I have to test) May need another battery)
7.4 volt 2800 mah battery to power one mega and either two or three Uno's.
One sensor shield, xbee shield, micro shield (May not use the micro shield)
Use I2C to talk to all the Ardunio's.
Relay for each motor, five total.
Two breadboards for wiring. This will do for now as I test.
Tilt sensor incase it falls over, stop the blades and drive wheels.
Light sensor so it will not cut at night.
Blade motors are ~6000 rpm with Banebot gearbox. Three blades about 6" in length.
Lawnmower is 12" wide and 1bout 22 inches long. Made for HDPE white material, two levels.
Cuts from the front as it moves forward.

Randy
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