Autonomous Electric Go-Kart Build

[Ted Meyers]

I'm rebuilding my Autonomous PRS vehicle from last years AVC.  I've mostly started the rebuild from the ground up.  I have two rails from an old garage door that I'm using as a frame, along with some steel construction struts from Lowes.  No welding, just bolting the pieces together, along with some plywood.   I built a steering column in order to test it =)  For now, it is one wheel drive on the rear wheel; in the future, I might add another motor to the other rear wheel, but it doesn't really need it.  The motor is a cheap 500W brushed motor from ebay (something like $58).  The ESC is also a cheap go-kart controller (50V x 100A) from ebay ($60).  It goes plenty fast with me on it, even up hill, faster than I feel comfortable, considering the steering wheel is a pair of vice-grips; maybe 15 mph going back downhill.  Oh yeah, and I mounted the chain sprocket to the wheel with a 3D printed mount -- I love my 3D printer.

Anyone else planning on entering what Sparkfun is now calling the "Autonomous Human Rider" class this year?

[Jon Watte]

It's growing in size :-)

I'm amazed you can get 50V 100A for $65. It's hard to just source the FETs and controllers at that price...

Maybe it's 100A peak and less continuous?

JW

On Apr 22, 2017 16:52, "Ted Meyers" <ted.m...@gmail.com> wrote:

I'm rebuilding my Autonomous PRS vehicle from last years AVC.  I've mostly started the rebuild from the ground up.  I have two rails from an old garage door that I'm using as a frame, along with some steel construction struts from Lowes.  No welding, just bolting the pieces together, along with some plywood.   I built a steering column in order to test it =)  For now, it is one wheel drive on the rear wheel; in the future, I might add another motor to the other rear wheel, but it doesn't really need it.  The motor is a cheap 500W brushed motor from ebay (something like $58).  The ESC is also a cheap go-kart controller (50V x 100A) from ebay ($60).  It goes plenty fast with me on it, even up hill, faster than I feel comfortable, considering the steering wheel is a pair of vice-grips; maybe 15 mph going back downhill.  Oh yeah, and I mounted the chain sprocket to the wheel with a 3D printed mount -- I love my 3D printer.

Anyone else planning on entering what Sparkfun is now calling the "Autonomous Human Rider" class this year?

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[Ted Meyers]

Here's the link to the ESC: http://www.ebay.com/itm/10-50V-100A-5000W-Reversible-DC-Motor-Speed-Controller-PWM-Control-Soft-Start-/301812872159?hash=item464572f3df:g:N3UAAOSwuhhXUOpp

Yeah, that is 60W, 100W max.  But that is still a great price, and is well within the specs of the motor I'm using -- it is a 24V, 500W motor after all -- it seems to peak at about 60A, when starting.

On Saturday, April 22, 2017 at 11:02:38 PM UTC-6, Jon Watte wrote:

It's growing in size :-)

I'm amazed you can get 50V 100A for $65. It's hard to just source the FETs and controllers at that price...

Maybe it's 100A peak and less continuous?

JW

On Apr 22, 2017 16:52, "Ted Meyers" <ted.m...@gmail.com> wrote:

I'm rebuilding my Autonomous PRS vehicle from last years AVC.  I've mostly started the rebuild from the ground up.  I have two rails from an old garage door that I'm using as a frame, along with some steel construction struts from Lowes.  No welding, just bolting the pieces together, along with some plywood.   I built a steering column in order to test it =)  For now, it is one wheel drive on the rear wheel; in the future, I might add another motor to the other rear wheel, but it doesn't really need it.  The motor is a cheap 500W brushed motor from ebay (something like $58).  The ESC is also a cheap go-kart controller (50V x 100A) from ebay ($60).  It goes plenty fast with me on it, even up hill, faster than I feel comfortable, considering the steering wheel is a pair of vice-grips; maybe 15 mph going back downhill.  Oh yeah, and I mounted the chain sprocket to the wheel with a 3D printed mount -- I love my 3D printer.

Anyone else planning on entering what Sparkfun is now calling the "Autonomous Human Rider" class this year?

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[Jon Watte]

I take that back. 100A 100V FETs are like $3. 

(You'd pay about as much for the gate driver, too)

So, twenty bucks in main parts, about as much in PCB/packaging/connections?

We live in the future!

JW

[Jon Russell]

I love the low profile, racing, steering wheel !

:-)

Jon.

[Jon Watte]

Here's the link to the ESC: http://www.ebay.com/itm/10-50V-100A-5000W-Reversible-DC-Motor-Speed-Controller-PWM-Control-Soft-Start-/301812872159?hash=item464572f3df:g:N3UAAOSwuhhXUOpp

Interesting! Will you drive this with a digital potentiometer, perhaps?

Or re-program it to use some other input method?

(What MCU does it use for "re-programming" ?)

Sincerely,

jw

Sincerely,

Jon Watte


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[Ted Meyers]

That is something I have not put much thought into.  Maybe attach a servo to a pot?!  Would electrically isolate things.  Or, just send an analog voltage to the input pin, will that work, probably?  A digital pot does seem like an obvious choice, and I've always wanted to try using a digital pot for something.

[Rich B (Roadrunner)]

That kart is REALLY nice. Good job...I'm definitely jealous. Looking at your photos of the 3D printed mount, did you match drill the holes in the wheel hub from the 3D printed mount? Why didn't you use the existing bolts/holes in the wheel hub? Were you constrained by the 3D printer bed?

[Ted Meyers]

Thanks Rich!

Mounting bolts:  Simply, the mounting holes in the sprocket did not line up with the mounting holes in the wheel hub.  I felt that it would be stronger to use bolts that went all the way through the hub, mount, and sprocket than to have 2 sets of bolts (one for the sprocket and one for the hub).  This did cause me to have to drill new holes in the hub that are not quite perfectly centered on the wheel (problem is my drilling skills), but close enough (I have noticed a little 'wobble')..

Ted

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[Jon Watte]

This did cause me to have to drill new holes in the hub that are not quite perfectly centered on the wheel (problem is my drilling skills), but close enough (I have noticed a little 'wobble')..

I had the same drilling "skills."

I went to a machining class, and learned how to use a vertical mill, and now my holes are all spot on :-)

I highly recommend it!

Many garages and workshops and whatnot may have a "Bridgeport" style knee mill in some corner, and may let you use it or rent time on it.

The maker space I'm a member of (Tech Shop) has one or two per location, too. (Benefit of the Bay area: There are three Tech Shops within 30 miles of me :-)

Sincerely,

jw

Sincerely,

Jon Watte


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