YAP - YABR (Yet Another Balancing Robot)

[packetbob]

Welcome to another YAP (Yet Another Project)
This time it’s a self balancing robot…
I was researching STM32 stuff (blame @Jarrett) and stumbled onto an interesting site…

http://www.brokking.net/yabr_main.html

While not STM32 based the balancing robot caught my interest mainly cuz I had a bunch of the needed parts gathering dust… So I decided to build one and figured I’d document the process here.

The one thing I did not have was the wheels. In the project he is using laser cut plywood to make them but I sort of wanted something better. I spent a lot of time searching AliExpress. I wanted a similar size (2ish inches) but with decent rubber… I also had to find something that would easily mount on the 5mm stepper shafts. While not really as cheap as I’d like I found these and ordered a set:
https://www.aliexpress.com/item/DC-motor-tire-wheel-coupling-combination-of-intelligent-robots-DIY-model-toy-car-accessories-aperture-3MM/1966875941.html

Since I had to wait for the wheels I went about gathering the parts I did have and figuring out what size board I would need.

Looks like a 7cm x 9cm proto will do the trick and luckily I had one.

One thing I was missing was the radio transceiver module. Looked around and ordered a couple of these as I had seen them used in some other projects:
https://www.aliexpress.com/store/product/1pcs-433Mhz-HC-12-SI4463-Wireless-Serial-Port-Module-1000m-Replace-Bluetooth-NEW/731260_32695273537.html

Next I thought about the frame. They used plywood for the prototype but I didn’t have any thin stuff to use. But I do have lots of aluminum angle so I decided to use it. I’m wondering if it will affect the rf signal but it will just be a frame so there will be lots of open area.

[packetbob]

Normally I would use a NANO for something like this but the PRO-MINI is even smaller (cuz it doesn’t have the USB/Serial chip onboard) and since I had one I decide to go with it as the NANO was a bit too large. The caveat is that you need a USB/Serial adapter to program but the programming pins can stick straight from the board allowing and easier connection…
And the CH340 USB/Serial board are really cheap…
And I shouldn’t have to make many programming changes…

[packetbob]

I decided to use a drawing program to figure out the best sizes for the aluminum. I figured better measure twice and cut once (though typically I do the complete opposite…

I’m going to use 1/16" x 1" angle. Tomorrow I will cut it to size and drill out the holes to mount the steppers. I’ll probably just pop rivet the pieces together to make the frame.

[packetbob]

Here is the stepper motor(s) I’m going to use:

It’s a NEMA17 instead of the smaller NEMA14 used in the prototype but they should work…
Mebbe I’ll need a bigger battery…

[packetbob]

So I cut up some aluminum angle

Used a square to align and drilled some holes:

Notched out where I want to mount the steppers:

Finished it up with a file:

Put it together with pop rivets:

And the final product:

[packetbob]

I got the wheels today and am pretty happy with them

They come with a heavy duty adapter to mount on the 5mm stepper shaft with 2 set screws

The wheel then mounts over the adapter and locks in with a screw and lock washer

They are a bit larger diameter (2.5" rather than 2") than used in prototype but it should not be an issue…
I don’t think…

[packetbob]

Mounted the PCB on the frame and attached the motors…

Next on to wiring up the circuit board… While normally I’d use sockets for the various modules I think I’ll solder them in place to keep a low profile (the sockets add 5/16" to the height)…

And hope I don’t need to replace any of them…

[mirong]

Very nice progress reports!

Hey, is that a TTY in the background?

[packetbob]

Yup… Found it in the trash… Seems to work…