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Powered wheelchair for the beach

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(@dubbadan)
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Joined: 2 years ago
Posts: 24
Topic starter  

Last weekend I finally got to do the first functional test of my biggest and longest project so far. It's a beach-going powered wheelchair for a friend who uses a powered wheelchair daily, but only has a non-powered one for the beach. There's still plenty of work to be done, but it was very satisfying to have it mostly together and working.

Here's a link to a 30sec video snippet of the very first test.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7410
 

@dubbadan That looks like quite the project. When you have the time you can show and tell us how it is made, including the mechanical and electronic systems. Many of us here are of an age that may be our next mode of transportation.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@dubbadan)
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Joined: 2 years ago
Posts: 24
Topic starter  

I would love to do that. I'll take some photos when I can, might not be for a week or so. Until then, I can list the main electrical and electronic components:

2 x 24V 250w DC motors with gearbox (salvaged from an old power wheelchair)

2 x ridiculously heavy lead-acid 12v batteries (salvaged from the same chair)

2 x IBT-2 h-bridge motor controllers (with extra heatsinks, in a jiffy box with a small fan)

Raspberry Pi Pico

Some extra power circuitry

Simple analog joystick

 

I also have a LiIon (ex- EV) battery made up to 36V that I'm considering using instead of the lead-acid monsters, but this would involve extra power-stuffery, time, money, etc.

 

The code I am using currently is mostly just simple if statements, which works ok, but is a bit clunky in terms of the joystick-to-motor response. I am working on something that will hopefully work a bit more smoothly. I originally wrote the code in C++ for Arduino, but have been learning MicroPython for the Pi Pico. It's been a long but (mostly) enjoyable learning journey.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7410
 

@dubbadan Keep in mind that the safe LiFePO4 battery is a drop in replacement for lead acid but 1/2 the weight (about 30 lbs) but expensive. You can make your own as well for a good cost savings, just don't cheap out on the BMS.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@dubbadan)
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Joined: 2 years ago
Posts: 24
Topic starter  

Thanks @zander. A while back I made up the battery pack to 36V nominal with LiIon 7.2V modules from a Nissan Leaf, with a hefty BMS installed. It's a beauty. I'm hesitant to use it because of the extra power conversion I'll need to make, which then means considering power losses and heat management. Also, I've been saving it for a different project, but it may be necessary to use it here due the problems caused by the weight of the lead-acid batteries.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7410
 

@dubbadan I don't have experience with that size of voltage drop, but at least in theory you should be able to get or make a DC to DC converter often called a Buck converter. You may find them in the Solar field, they generally work in units of 12V and there are lots of reasons to go from 36V to 24V. I will have a look at my source to see if they exist.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
Posts: 7410
 

@dubbadan Try this one https://daygreen.com/en-en/collections/36v-48v-to-24v or

https://dakotalithium.com/product/24v-36v-48v-dc-to-12v-dc-10a-dc-dc-converter/

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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