Make a Littlebits inchworm with clever circuits

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We’ve just come to the end of a long weekend, and Liam was looking for something different to do. He hasn’t used his Littlebits set for a while, so we brought it out and he made a Littlebits inchworm. It was partially inspired by his Lego Wedo Inchworm a couple of weeks ago, but we also found a great guide here.

What is Littlebits?

Littlebits is an electronics kit by Sphero. The bits snap together and line up perfectly with tiny magnets embedded in the ends. Sphero have included some great features which help beginners get started with circuits. The magnets on each bit can be connected in only one direction, so there’s no risk of getting pieces backwards. Each bit has an arrow showing which way it should go. All the pieces are named, which helps with learning. Different types of bits are colour-coded differently (power = blue, inputs = pink, connectors = orange, outputs = green), so that it’s easy to identify their various functions.

How to make a Littlebits Inchworm

It’s nice to have a project that uses a lot of materials you’ve already got around home. Here’s what you need:

• Cardboard
• Ruler
• Pencil
• Wooden skewers, toothpicks or straws
• Tape
• Wire or a paper clip
• Rubber bands
• Craft knife
• String (optional but recommended)
• A weight (spare battery or a couple of coins)
• p4 power bit
• o9 bargraph bit (optional)
• o11 servo bit
• Littlebits battery pack

Build the cardboard inchworm

Start by building the cardboard base for your Littlebits inchworm. Cut your cardboard into a 8x30cm rectangle. Liam glued coloured paper to both sides of his cardboard to decorate his inchworm, which is completely optional.

Fold the rectangle in half across its length, and then fold back 5cm of the ends. That gives you the general shape of the inchworm.

Poke holes near the corners of the A-frame panels, about 1cm in from each side. Thread a wooden skewer in through the top hole and out through the bottom, to give a stiffened edge. Do that on all four sides.

On one of the upright panels, cut a rectangle in the centre. This is where the servo arm will swing. Make the rectangle approximately 1cm wide and 5cm long, leaving a solid area above and below.

Add some extra wooden skewers behind the rectangle cut-out to give it more bracing at the opening. Use packing tape if you’ve got it – it holds very firmly, which is what you want here.

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On the underside of the feet, use the pencil to mark out small triangles. Pay close attention here to which way the triangles are facing, because these are what make the inchworm travel forwards. On the side with the cut-out for the servo, the triangles should be pointing outwards, towards the edge of the cardboard. On the foot at the far end, draw the triangles pointing inwards towards the cut-out. Before you start cutting, make sure that all the triangles face the same way.

Cut two sides of each triangle like in the pictures. Then, use a spare skewer or your pencil to push each notch down, so that you make little spikes on the bottom. When the inchworm moves forwards, the spikes will flatten, and then they’ll grip in the carpet so they can’t slip backwards on the next movement.

Fix and secure the servo

The servo drives the inchworm along, so it needs to be fixed very securely. Take the time to get this bit right, and the rest of the project will go smoothly. Roll a piece of tape over on itself to make it double-sided. Fix it to the back of the servo, and then press the servo into place so that the arm can swing through the slot in the cardboard.

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If you’re using a paperclip, unfold it so you’ve got a straight line. If not, cut a piece of wire approximately 10cm long. Hook one end through the tip of the servo arm and bend it into a loop so that it holds firm.

Make a small hole in the opposite panel of the inchworm, a few centimetres from the top. Poke the other end of the wire through the hole, and fix it to the panel with tape. You want this to be as firm as possible, because this is what pushes and pulls the panels.

When you’re happy with the positioning of the servo and the wire, tie some string firmly around the body of the servo. It just helps hold it firmly in place.

Build the Littlebits circuit

The Littlebits inchworm uses a very simple circuit: power pack > switch > bargraph > servo.

You’ve already got the servo fixed in place, so drape the wire up and over to the front panel. This is the last piece to connect.

Place the battery pack underneath the servo, and hold it in place with a couple of rubber bands. Clip the power cable onto the battery and bring the wire up and over to the front panel.

Rest the p4 power bit on the bottom of the front panel and use another rubber to secure it. Fix the o9 bargraph onto the power bit. The bargraph is actually just being used for decoration on this project, because it’s got nice bright lights. Click the 011 servo bit onto the end of the bargraph to complete your circuit. Plug in the power cable to the power bit, and turn it on.

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Watch your inchworm go!

Well done for completing your inchworm! Did you have fun putting it together?

Let us know in the comments!

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