‘Will it conduct?’ Project

will it conduct cover

Task: To recognise some common conductors and insulators; To use selection within a program
Difficulty: Intermediate

For this project you will need:

  • One Crumble with USB lead;
  • A computer with the Crumble software installed;
  • A battery box  with batteries (not rechargeable);
  • a bunch of croc-leads;
  • a Sparkle Baton (or other Sparkle-based Crumbs);
  • a push switch;
  • a cardboard box;
  • paint mixed with PVA;
  • a paintbrush;
  • a craft knife or scissors;
  • a pencil;
  • and some sacrificial newspaper and card.


1 To start with, we need to gather all of our materials.


2 Before we go any further, we need to mix our PVA glue and paint, and paint our box.

3 We used a particularly shiny box, so it needed two coats of paint. Once finished, leave it to dry.


4 Layout your Sparkle Baton and switch.

5 With a pencil, mark where each crocodile clip will poke through the card and connect to your components.


6 Hopefully you will have something similar to the following. Note that we have marked inside and outside each hole. We have also put two crosses where we want two leads to poke through.

7 Carefully cut along each mark that you have made. If using a knife, it is a good idea to put a sacrificial piece of card underneath.


8 Carefully poke the jaws of the crocodile clips through the holes cut earlier.

9 Once you have inserted all of your leads, attach your switch and Sparkle Baton.


10 Now we need to wire up the Crumble. Use the following steps to help.


11 Start off by connecting the battery box to the Crumble. Notice the +ve and -ve connections.


12 Now we are going to connect the Sparkle Baton however, you can use any type of Sparkle-based component you want.


13 Then attach two croc leads, which we will join with our material. You can use A, B or C.


14 Finally, connect a push switch. Although we’ve got the power coming from the Baton, you could clip to an exisiting +ve connection, but this is more likely to detach itself. As for the input into the Crumble, use a free IO pad (A, B, C or D).

Now we want to work on programming our Crumble.


15 To begin with, lets set up our basic conductivity tester. When a material is connected between the two loose croc leads that conducts electricity, A becomes HI, which will turn the Sparkles green. If there is no connection made, or the material is an insulator, then they will be red.


16 To make our tester more functional, we want to start it at the press of a button. Notice that we have used two ‘wait until’ statements. The first waits for the button to be pressed and the second waits for it to be released. This makes the device more user friendly, allowing someone the time to press the button and move their finger off of it before the program continues. It’s also more of a fail-safe way than using a wait statement, as someone could break the program by keeping their finger on the button, whereas this method waits until their finger is off, before running the rest of the code.


17 Finally, we want to our conductivity tester to display the results for a set period of time, before turning off again. We can achieve this by putting a wait statement at the end, and then turning the Sparkles off. Our example shows the results for four seconds.

Once programmed, you can carefully place the components inside the box, and you’re ready to go! Our box was a bit of a squeeze, so we’d recommend using a larger box, or designing your own case from scratch. Just connect up a material, and press the button!

If you have a go at this project, or any other, we’d love to see! Get in contact with us via emailFacebookTwitter or our Forum, and we may feature your work!

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