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Science with the Crumble: Test your reactions

HYPOTHESIS: Humans react more quickly to something they hear compared to something they see.

In order to test this hypothesis, we used:

  • Laptop with Crumble software installed
  • Crumble controller & Sparkle baton
  • Crumble-friendly battery box; 3 AA batteries
  • Croc-leads and a micro-USB cable
  • “Crumble-friendly” switch and buzzer

The Crumble, Sparkle baton, switch and battery box are connected in the same way as the last reaction timer project (although the switch is connected to input A, rather than B). The program, however, is much simpler:

At the start, all the Sparkles are turned off. The Crumble waits for a random period of time (between 2 and 6 seconds) and then begins lighting the Sparkles in quick succession (every 50 milliseconds). The aim of the game is to press the switch as quickly as possible. Note: you have to hold down the switch until you have read your “score”. When the switch is released, the game restarts. Joseph & I discovered that, after a bit of practice, we could consistently press the switch after 4 or 5 Sparkle LEDs had lit up (i.e. after 150-200 milliseconds). 

In order to test whether we could react more quickly to a sound, a buzzer was then connected between “output B” and “Ground” (a “-” pad on either the battery box, or the right-hand side of the Sparkle baton). The program was modified so that the buzzer turns on at the same time as the first Sparkle LED:

For a fair test, you have to close your eyes while playing – but remember to open them and read your score before releasing the switch! Now we found that we could press the switch after 3 LEDs were lit (100 ms). 

So, our small sample does support the hypothesis, above. Further reading suggests that humans react even faster to touch-stimulus: can you think of a way to measure that with the Crumble? If you do the experiment with a larger group, let us know your results and we will publish them, here!

Crafty Crumble Creations: A “police” helmet.

Whenever our 2-year-old finds something with a flashing light on it, he holds it on top of his head and runs around shouting “nee-nah nee-nah”. I decided we would make a flashing helmet, using a variable to set the Sparkle colour and brightness in the Crumble Software.

We used:IMG_9210

  • 1 laptop with Crumble software installed
  • Crumble controller & Sparkle
  • 1 battery box with croc-clip attachments; 3 AA batteries
  • Croc-leads and a micro-USB cable
  • A switch/Switch Crumb
  • Plastic dome; glue; tissue paper; blue paint; cardboard; & sellotape

Connecting the Crumble

Screen Shot 2015-05-18 at 16.49.34This diagram shows one way of wiring up a Crumble, battery box and switch. The switch is connected to Pad “A” on the Crumble and to the +ve terminal of the battery box. By default, the input pads are at zero Volts (“low”). When they are connected to the batteries they receive 5 Volts (“high”).

In this case, when the switch is pressed, input A is connected to the batteries. In the software, therefore, we can use the “Wait until A is Hi” block to tell the Crumble what to do when the switch is pressed.

The croc-leads on the right-hand-side of the Crumble connect to a Sparkle (see previous blog posts)

IMG_9053The photo, left, shows the Crumble and Sparkle connected with a standard push-to-make switch. There are a couple of problems with this set up, though. Firstly, 2 IMG_9056croc-clips have to connect to the top-left “power-in” pad on the Crumble. Also, the tips of the two croc-clips connected to the switch are very close (see right) and can easily short-circuit.

IMG_9061A tidier soloution is to use a Switch Crumb (the one pictured is designed and sold by 4tronix ). This has pass-through power lines, like the Sparkles, meaning it can be connected in line with the battery box and the Crumble.

A pad at the bottom of the Crumb connects to an input on the Crumble (the yellow wire in the picture), in this case to Input A.

Programming the Crumble

Screen Shot 2015-05-18 at 15.25.18Within each Sparkle there are actually 3 LEDs: red, blue & green. Their relative brightnesses are varied to create any colour from the visible spectrum. The RGB Sparkle block (below) allows us to precisely control the colour, by setting each of the LEDs to a value between 0 (off) and 255 (maximum brightness). In this program we keep red and green at 0, only changing the blue.Screen Shot 2015-09-19 at 08.37.25


The Crumble program used is shown above. It continuously checks to see if Input A is high (i.e. if the switch has been pressed). When it is, a loop is executed five times. This gradually increases the brightness of the blue LED within the Sparkle then decreases it (by incrementing the variable “t” from 0 to 200 then decrementing back to 0).

Constructing the HelmetIMG_9191



The plastic dome came from a supermarket package of profiteroles. A hole was cut in the top so the lid of a fabric softener bottle could be inserted. We glued bits of torn tissue paper all over the plastic (a la CBeebies “Mr Maker”) so that it could be painted blue.

The Sparkle was positioned so that it shone up into the the bottle top and the rest of the electronics was sellotapIMG_9205ed into the dome then covered with a circle of card, leaving the switch exposed.

I was planning to construct some sort of headband, attached to the bottom of the dome, with the switch mounted on it like a badge. The two-year-old, though, had already decided we were done. After that, he was never still enough for me to take a better photo than this (see right), so I think I can claim the project was a success!

DISCLAIMER: Clearly this is not a “toy” that would pass any of the safety tests required to make it suitable for under-threes.  The construction of the helmet was an afternoon distraction and our child was closely supervised at all times.