Author Topic: Jazzy select motors and motor controller interfaced for RC  (Read 1096 times)

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Offline headrcTopic starter

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Jazzy select motors and motor controller interfaced for RC
« on: July 25, 2013, 09:09:22 PM »
Hi everyone ....a Newbie here.  I recently acquired a Jazzy select electric wheelchair that I want to use the motors, batteries and possibly other electronics for a RC controlled lawn mower (and other tasks).  I have not been able to find an answer to this question.  Why would I have to buy something like a Sabretooth motor controller when there obviously is one in the Jazzy.  Could that motor controller not be interfaced with an RC set and be controlled by it?  I know I may be missing something here ....but if it can be done ...it saves another $140 or more to do what I want to do.  Great forum here ....and I know I will learn a lot !

Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #1 on: July 26, 2013, 08:42:17 AM »
I also acquired two motors, wheels (12"), a controller, and joystick that I have just started to build a robot with.

The motors are 24v @ 3amps, 100rpm. Took the controller apart and it uses 8 N-channel MOS fet's. (2sk1426)

I am doing the same thing that you are going to do. This is where I am at now. Built a frame using angle iron just bolted together. Everything works the way it should, of course everything is controlled for safety reasons.

Testing in the house wasn't a good plan, got hole in wall that I have to fix now.

Went to radio shack and bought a RC car for the plastics of the controller. (30$) Took the controller apart and there is lots of room for modification. Gave the car (red porche) to the neighbour's kid.

This is my plan to make it wireless, after I take some measurements for this motor controller.
I will be using 433mhz transmitter and receiver along with the pt series encoder and decoder. A few bucks.

I will be using the attiny4313 that has 4k of flash and built in PWM. I have all the parts, just time now involved.

I have two controllers so I am going to cut the fet's off with my bandsaw keeping them attached so I can screw it back to the case. (heat sink)







Offline headrcTopic starter

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #2 on: July 26, 2013, 10:52:57 AM »
So you are using the original motor controller from the wheelchair then.  Still trying to figure out why others don't do this.  Candidly, I am not technically up on everything you outline here.  I will probably have to get to that point ...but would like to know if I could not just purchase an RC set made by someone like Futaba and get everything under control using the wheelchairs motor controller.  I know I could buy a Sabretooth or equivalent motor controller and I may end up doing this if the motor controller from the wheelchair cannot be used without a lot of hacking (and learning how to do this). 

Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #3 on: July 27, 2013, 08:49:17 AM »
I think why ppl don't do this, is that you are at the mercy of the controller such as speed and acceleration. For example, with my unit there is a switch on the joystick, off, drive a, and drive b. When I switch to drive a, then I move the joystick forward, the acceleration and speed are predefined by the software (firmware). Same with drive b. With turning, left or right to the extreme, it will spin in a circle, one wheel forward and the other reverse, also the speed is reduce for safety reason. Lot of design put into these controllers for safety.

With that being said, I am going to do what you suggested and use my cheap RC transmitter and receiver for basic control. I took my transmitter apart, there is regular speed and turbo speed, on or off, same with left or right, nothing fancy, servo will turn hard left or right. Put my Oscope and there was nothing to measure except on or off.

Checked out the Futuba online but could not find any technical info on them. I am sure there is other members that can help us there.

Will take some more measurements of motor controller today to see what will be involved to hook up receiver. 

Offline headrcTopic starter

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #4 on: July 27, 2013, 10:43:29 AM »
Hi again ...you are certainly a lot more knowledgeable than me (as many others here are) regarding the whole electronics aspect of this.  So anything you discover on how to do this please let me know.  Another thought going through my mind is to just sell the wheelchairs motor controller on fleabay and use the funds to buy something like the Sabretooth motor controller.  They seem to be pretty easy to set up ...and for a newbie I like that.  If I could basically do a swap that way with no major cost it could make life simpler ...unless it turns out hacking the existing wheelchair controller is no big issue.  It would be nice to also have this thing under manual control as well ...which would be an advantage of hacking the wheelchair motor controller.  My application for this thing when up and running will be taking it over some fairly rough terrain at times so I definitely to make sure it is under good control.  As far as RC set .....I have not done a lot of research there yet.  I just poked around and found the Futaba and it seems to be a recognized name and commonly found ...which indicates possibly something used might also be found that will do what I want to do.  In my reading it seems that PCM is the best method for what I want to do ....so I am looking for that first unless I am guided otherwise.  Thanks for the response and please do let me know what you discover.

Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #5 on: July 30, 2013, 01:21:49 PM »
There is a 15 pin color coded wire connector from the joystick to the controller, three are (nc), no connection, three are 5vdc, one is gnd, one is driveA 5vdc and driveB 0vdc or gnd. One is for self test from the eeprom. It flashes the LED for the self test, nothing will work until the test is complete.

Two other pins (wires) from the joystick are at 2.5vdc. One wire is used for forward and reverse and the other is used for left and right. Using the multimeter, full forward, the voltage goes up to 3.8vdc to the controller that turns the motors forward. In reverse the voltage drops to .8vdc, again on both motors. Reverse is always the same speed. (safety reasons). For turning it will slow down one motor or both, again for safety reasons. The turn radiaus is central to the wheels.

Getting to what is going on with fet's. They are triggered @ 10us on (high about 12vdc) , then off for 10us. When the fet's are on, the fet's are being modulated on and off at different pulse periods to regulate the speed, again for safety reasons.

Now the fun begins





Offline headrcTopic starter

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #6 on: July 30, 2013, 07:18:30 PM »
Ok ...thanks for this info.  Keep me posted on how this goes for you ...although right now I am feeling like using something like the Sabretooth motor controller will be a lot simpler.  I talked to them today ...and got an indication it is pretty easy to set up.  Easy is good for me ...andthen maybe I can sell the Jazz controller to help pay for it. However if you find it is easy to do ...yippee!

Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #7 on: July 31, 2013, 11:28:20 AM »
Oh ya for sure, for a couple bucks you can have a working machine and concentrate on your objective, a rc lawnmower. If you go that route, keep me updated. I will be needing to know what kind of hook your using and and others things like weight and torque. The tires on my wheels seem kind of skinny to work on grass let alone trying to push or pull something off the pavement.

Here's where I am at now.
Setting up comminications link. Using trans/receiver(433mz) modules and encoders/decoders.
Have to order D/A converters. While I am waiting, write program to send data.  Will keep you updated.


Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #8 on: August 07, 2013, 08:59:31 PM »
Hiya again, just an update.

Took apart the controller to investigate what is going on. There are two boards, one is the controller that has a self-test. This controller board consist of a micro, eeprom and a lot of discrete components. The second board is the power board for the fet's, h-bridges, brakes on so on.

I took a lot of measurments from the joystick to the ribbon cable that connects the two boards and measuments to the gates on the fet's. The technology is 20 year's old (built 1993) and I have come to the conclusion that it is not worth the time to modify or play with it. This probably the reason why  nobody bothers to try to modify. Like the fet's dont have built in diode protecting, the data sheet warns you of that.

I said earlier that I was going to cut the fets of the board and put a new front end on it, again, not a good plan. Still fooling around with old technology.

When I first joined this forum I spent a lot of time reading the FAQ'S and a learn a so much, especially the h-bridge and the way it works for programming purposes. Also KISS, keep it simple stupid. But I still like to build my own, learning curve.

So, new plan, I am going to build the schematic that I got off the FAQ'S where there are two n-channel fet's and two p-channel fet's per motor, as the controller board that came with this, have n-channel fet's only. I also found a schematic for n-channel, but, I will stick with schematic that I got here.

I spent a week playing with this motor controller and learned a lot as I have the equipment, multimeter,O-scope and logic analyser. I am very impressed with the old technology that has the safety that is built into it, the firmware. (eeprom)

Starting over, I have made a schematic using pcbexpress to make the pcb board for what I am going to call the power board, fet's and cap's, got all the equipment to make pcb's. I have my solderless breadboard that I am going to use for the controller part, u-controller, transister's for drive and so on.

I will keep you posted as I progress.






Offline jlp

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #9 on: August 12, 2013, 11:18:44 AM »
Built pcb for a motor controller, now I have to wait for parts. Hopefully I can start contruction by the weekend.

Offline headrcTopic starter

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Re: Jazzy select motors and motor controller interfaced for RC
« Reply #10 on: August 15, 2013, 12:19:43 AM »
Well you are a lot further along than me ...other projects are in my way (like mowing the lawn and weedeating!).  Although I do have most of my components.  I got the Sabretooth 2x60, four motors and even picked up an old lawnboy riding mower that looks like the frame and everything will work great for this.  I am struggling with what to do about tires etc.  The tires on these motors are not going to work ....too small.  And I have not pulled the motors off the wheelchairs yet ....but I got a feeling they are keyed shafts from all the other Jazzy motors I have seen ...and short ones.  So putting on bigger hubs, wheels and tires may require some type of re-engineering ....at the very least probably a shaft coupler ..unless I do some type of transmission setup.  I would like to avoid that if I can.   I just don't have the time to study all the electronics to build that stuff from scratch like you are doing...wish I did but this thing would take even longer to get together because my electronics knowledge is not at the "board level".   Keep me posted.

 


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