Simple Micro:bit Robot With Lego Technics Wheels

This instructable is all about using a very simple chassis using 2 pieces of 5mm perspex which I cut and drilled so I could get a Micro:bit robot up and running as quickly as possible.

Just to set the scene I didnt use any electric tools except for a dremel drill.

I also wanted to add some Lego Technics wheels I had.

I used the following materials:

2 x Micro metal gear motors (N20) 1:298 Ratio https://shop.pimoroni.com/products/micro-metal-gea...

2 x Motor brackets for the N20 https://shop.pimoroni.com/products/pimoroni-gearmo...

2 x Lego shaft adaptors for the N20 shaft to Lego cross shaft. https://shop.pimoroni.com/products/micro-metal-gea...

2 x Lego technics wheels https://www.amazon.co.uk/LEGO-TECHNIC-Tire-black-w...

1 x A4 sheet of 5mm tinted / clear perspex - you don't need much but they are normally sold in A4 size sheets

1 x Kitronik micro:bit motor controller https://www.kitronik.co.uk/5620-motor-driver-board...

1 x caster wheel - I used a DIY one I had from homebase or B&Q in the UK, the type that fit on the bottom of a chair or small table leg.

I use used some plastic PCB standoffs to mount the 2 perspex boards

1 x A4 5mm perspex sheet - you only need about half this so perhaps make 2 bots :)

https://www.amazon.co.uk/Malayas-Stand-off-Assortm...

1 x battery pack either AA or Lipo up to 6v, I had to use a power step down regulator as I used a 2S 7.4v Lipo battery, but I would recommend 4 x AA giving you a nice and easy to use 6v supply to the Kitronik motor board.

Step 1: Measuring, Cutting and Drilling the Perspex

For my design I wanted to have a larger lower layer of perspex, with a smaller one on top where the Kitronik motor control board would sit, and the micro:bit would slot into that.

This design creates a space for wires, battery and power regulator if you need to use one. This will be covered later on.

I positioned the motor board onto the perspex and marked it out about 1cm wider than the board to give me some space to use the spacers between the 2 perspex sheets.

Note: Leave the covering on the perspex until you have cut and drilled it, this stops tools slipping or scratching the shiny perspex surface.

The smaller piece I measured to be the same width as the lower layer but was shorter in length. Just big enough to allow the motor board to sit easily with about 1 cm border around it.

I use a perspex cutter its like a stanley knife with a hooked end, and a metal ruler, to lightly score where I had marked I wanted to cut the perspex.

Once scored a number of times, you can lay the perspex on a sharp corner of a work surface or table, and then hit the over hanging bit of perspex with the palm of your hand, whilst holding firmly or clamping the other said on the surface you are using. This will snap the perspex if you have done it right, if not rescore the line you have marked.

Drilling the holes

Lay the motor board on the smaller of the 2 sheets in the position you will want it to be, use a small screw driver or sharp point to mark where to drill through the holes in the motor board, so using this as a template.

Also mark 4 holes to the side of where the terminal connectors are for the motors and 2 holes where the power connects.

Step 2: Adding the Motors and Caster Wheel

Once the holes are all drilled the motors can be fitted with their brackets, using the supplied nuts and bolts.

Note: If you can get the brackets that come with the metal and not the nylon nuts and bolts they work much better, and hold your motor in place securely.

The lego adaptor for the wheels can be put on each motor output shaft now.

I used some lego cross axel cut to size to push through my lego technics wheels and into the adaptors.

This is a great way to use those old lego wheels you might have and they can be any size, change your design to suit.

Step 3: Adding the Power Supply

Note: The Kitronik motor control board can take any battery input up to 6v, I wanted to use a 2S lipo and so needed to use a voltage stepdown regulator to get it to 6v from the Lipo 7.4v.

But if you are using 3 or 4 AA batteries you will be fine, and it will allow you to connect easily your choice of battery power, its a good idea to also add a switch to the + battery to Kitronik Motor board.

Step 4: Wiring It All Up

Using the wiring diagram here add the wires from the motors to the Kitronik motor controller.

You can choose to use motors that come with headers you can plug straight in with jumper wires or those you have to solder, so select the motor that will fit your experience.

Step 5: Testing Your Setup

I would advice using the Kitronik datasheet which has example code and how to write the Micro:bit code to get you started.

https://www.kitronik.co.uk/pdf/5620%20Motor%20Driv...

You can follow more of what I do here at my website: www.inventar.tech

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