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Step 37Working
Here it is balancing.
This version has same motors and motor controller as my previous twin wheel self balancing skateboard so should perfom the same.
Wheelbase is 24cm but if you spaced them further apart clearly you could build a Segway style vehicle.
The idea is that you just bolt whatever you want to the top of it, Segway, skateboard deck, R2D2 or whatever takes your fancy! One of those R2D2 trash cans if modified would fit just perfectly on top.
Main parts (all new):
Sabertooth £97
Motors: very variable on ebay but about £35 each
Chain: £9
Arduino: £20
IMU: £52
Razor E100 rear wheel sets: £24.99 each from a big online electric scooter shop spares department.
Total £273 including purchase tax which I think is pretty good for any self balancing vehicle. Batteries would take you over my £300 target but not by much. Also compares well with cost of conventional 4 wheeled (one motor on one of back wheels) electric skateboards.
UK pound weak at present and Sparkfun and Razor scooters are US based, which suggests that you could do this at even lower cost in the US.
Might possibly be worth trying to buy a used Razor E100 electric toy scooter as this would give you one rear wheel unit, one motor (but might be too small), some batteries to get started with and a charger, then buy the rest as above.
This version has same motors and motor controller as my previous twin wheel self balancing skateboard so should perfom the same.
Wheelbase is 24cm but if you spaced them further apart clearly you could build a Segway style vehicle.
The idea is that you just bolt whatever you want to the top of it, Segway, skateboard deck, R2D2 or whatever takes your fancy! One of those R2D2 trash cans if modified would fit just perfectly on top.
Main parts (all new):
Sabertooth £97
Motors: very variable on ebay but about £35 each
Chain: £9
Arduino: £20
IMU: £52
Razor E100 rear wheel sets: £24.99 each from a big online electric scooter shop spares department.
Total £273 including purchase tax which I think is pretty good for any self balancing vehicle. Batteries would take you over my £300 target but not by much. Also compares well with cost of conventional 4 wheeled (one motor on one of back wheels) electric skateboards.
UK pound weak at present and Sparkfun and Razor scooters are US based, which suggests that you could do this at even lower cost in the US.
Might possibly be worth trying to buy a used Razor E100 electric toy scooter as this would give you one rear wheel unit, one motor (but might be too small), some batteries to get started with and a charger, then buy the rest as above.
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I found a website where you can buy Razor parts (razorama.com). They sell three kind of rear wheel assemblies, for different versions of scooters. Does it matter which one to get? Will the teeth on the sprocket match the one on the motors you find on ebay?
The Chinese electric motors sold as "scooter motors" have sprocket on them which fits this chain.
So, not sure what the 3rd type of wheel is but certainly for 2 of them the chain is the same type.
Well, there's three types, depending on the version E100 you have.
See this page: http://www.razorama.com/e1scpa.html
The page doesn't say what the actual differences are between versions... Only that you should pick the right version or it won't fit, so there must be differences...
Perhaps I will buy bigger wheels like these: http://www.razorama.com/e300rearwheel.html
For doing a bit Segway off-roading :-)
It can supply 25A per channel. (50A peak)
Watts is Amps x Volts so can theoretically cope with 600 Watts per channel.
So, 29V - maybe risky. 350W no problem by the look of it.
Check out combat robot websites if you want to look at other makes of controller that will take higher voltages, lots of them out there. Sabertooth is just quite easy to set up, has lots of modes, just 2 input wires, and current overload protection which is why I chose it.
OSMC for example has 5 input wires as opposed to just 2 on sabertooth so a little more fiddly to set up, bearing in mind I was trying to make this project as easy as possible to build.
Basically you let the balancing algorithm do its job then when it has worked out the motor speed it wants, add a bit to one motor setting and subtract same amount from the other depending on the pot value.
If you look at the code you will see what I mean.
I have also just worked out some code to make the second gyro control the rate of turn proportionally to the pot setting.
Maybe I should post 2 sets of code. Basic to get it balancing (the most important part by far), then another set with some extra features added.
John
One question. I have two lead acid battries that are for a lawn tractor. They're not as big as full car batteries, but a bit bigger than the ones you show here. The question is, would they have enough juice to do things like climb hills? I'm using big knobby tires so I would like it to be able to handle grass etc. Do you think these motors with lead acid batteries would hack it?
Lead acid batteries would give high current no problem and get you up hills, the endurance would be the unknown factor. Huge amount of discussion on this on ebike forums by the way. They obsess over battery types / motor ratings. Vehicles are different but the maths is probably similar.
For a big machine going up hills the bulletproof way is to use two OSMC controllers. These can take huge currents, but cost a lot more than Sabertooth as you need two of them. The Sabertooth is described as being for "medium sized robots" You need something that will run uphill with maybe 100-120kg total all up weight.
This is where the costs and the size of the machine start going up. Really big motor controllers are not cheap.
Take a look at this website for example. It is a segway clone called the "Meta" by Geoff Bennett with biggish lead acids and two OSMC's. It illustrates these points.
www.netcraft.com.au/geoffrey/meta/
Based on original segway clone by Trevor Blackwell.