Steppy Mk II

wheeled robotic platform

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A simple wheeled robotic platform for various robotic competitions.

The goal of this project is to create a versatile robotic platform for robotic competitions.

It started with a very primitive PCB design that featured just a few, mostly through-hole components and evolved into a much more complicated design with over a hundred SMD components.

Main features:

  • NXP's FRDM dev boards, Arduino compatibility
  • Two NEMA8 stepper motors
  • Fits onto 100x100mm PCB for cheap manufacturing
  • RGB LEDs
  • OLED display
  • Joystick
  • Buzzer
  • I²C battery voltage sensor
  • Interchangeable sensor board

Features in more detail

FRDM dev boards, Arduino compatibility
I initially started with my trusted FRDM-K64F dev board and later reduced the number of used pins and added the ability to switch to 5V logic levels for Arduino compatibility.
There I made an error by not knowing that Arduino Uno has SCL and SDA connected to pins A5, A4. This makes I²C bus unusable if those two analogue pins are used.

NEMA8 stepper motors
I used Pololu's 20X30mm NEMA8 stepper motors paired with DRV8834 Low-Voltage stepper driver.
Not a very wise choice. These motors have a problem with tight turns (especially with four wheels). For the next iteration, I will change to some geared stepper motor for added torque and one of the Trinamic drivers.

Economically manufacturable PCB
The PCB is little bit bigger than 100x100mm, but JLCPCB still accepts it as $2.00 order.

There are nine WS2812 RGB LEDs on the underside. These can get quite bright and add a bit of visual flare.

OLED display
128x32 I²C OLED display enables for easy interaction and configuration.

One tiny SMD digital joystick can be used for interaction. Using it without the 3D printed cap won't make your fingers very happy though.
In the second version (Mk2V2), I used I²C ADC and some resistors to save a few pins.

Simple audible feedback. The OLED display is quite slow, so this can be very useful.

I²C battery voltage sensor
The whole thing is powered by 2-cell LiPo battery, so this allows to monitor for over-discharge.

Interchangeable sensor board
Easily exchangeable sensor board makes developing additional designs very easy

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