μBot [educational floor robot]

This is μBot, a very cheap, but all-round floor educational robot.

I teach underprivileged children as a volunteer and I need a cheap, but very flexible robot. I didn’t find one, so I made this. It’s my first PCB project and I’m not an engineer… So, every tip and advice are welcome. :)

I think most of the educational robots are overpriced (because of ads, resellers, etc.). However, our children need them so much. Algorithmic thinking, problem solving, makers culture… Just some scope that these robots develop.

My planning aspects were:

1. It must be as cheap as possible.

1.1. nonprofit
I will be a primary school teacher. I want to create opportunities for children, not profit for myself. :)

1.2. DIY
I designed huge solder pads, and every component can be THT (except the ESP8266). I think THT soldering is much easier for beginners. I hope, with the PCBWay’s affordable service everybody can afford an educational robot. The components are affordable, the soldering isn’t difficult…

1.3 cheap components

I tried to leave out every extra cost. I designed for DC motors (more common and cheaper), and I tried to fine-tune the engines with software (PWM, soft start, …). I leave out the encoders too… Well, I think some inaccuracy is acceptable. (It doesn’t obstruct the educational goals.)

2. It must be expandable.

2.1. protoboard
It has 2.54mm raster and mounting holes for the 3x7cm protoboards.

2.2. turtle HAT
We can control the μBot without smart device / PC. Forward and backward "steps", 90° turns, pause, clear… Like other floor robots. However, there are useful functions like undo and loop (details in the video). The turtle HAT: https://www.pcbway.com/project/shareproject/turtle_HAT_for__Bot.html

2.3. drawer HAT
Well, it will be a BOOT (or what…). It will be under the μBot (when we need it), so we can control with turtle HAT. It will have multiplexer and stepper motor driver. However, it's under designing.

2.4. jumpers
The motor driver can be disabled, so we can gain four more GPIO pins. We can choose the motor voltage too: 5V or the supply’s voltage. So, μBot can be a floor robot and a race car too. The are other comfortable jumpers: for sketch uploading (GPIO 0 & GND), for deep-sleep (GPIO 16 & RST), the main switch…

2.5. WiFi
I chose ESP8266 because it’s cheap and the WiFi capability helps to make more complex programs. In addition, we can gain four more GPIO pins (they work in the turtle HAT’s Charlieplexing). 

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About the pictures...

The green one is my last order. I like black solder mask more, but the time matters... :) From my last order I made only some minor changes (spacing some traces and THT holes). You can see on the black ones.

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BoM

1 x ESP8266
1 x SN754410

1 x AMS1117-5.0 (or L7805)

1 x AMS1117-3.3

6 x 0.1uF capacitor

1 x 1uF capacitor

1 x 100 uF capacitor (tantalum/elect.)

6 x 10k resistor

3 x terminal connector

3 or more jumpers

and a lot of headers

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This project is supported by the úNKP-18-1 New National Excellence Program of the Ministry of Human Capacities of Hungary. I learn a lot about PCBs and I hope I can design other ones for our children. :)