Skip navigation

by LDR (age 10) and Thermistor (age 8)



Last Halloween we saw a brilliant Dalek pumpkin in a Cambridge college quad. It had a candle in and looked sinister but funny at the same time. We decided to make one ourselves this year (Halloween and Doctor Who are big on our street).

 

For Christmas, we got our first Pi (thank you @drlucyrogers) , loaded with NodeRed. We did the traffic lights and a game, so we got ambitious. We were going to make an operational NodeRed pumpkin Dalek (not fully operational - that would be terrifying).

 

Choosing the Materials

 

Eye stalk and LED: We used a clear plastic pen for the stalk, with a blue LED, and a transparent lid on the end. We used card circles for the rings.

Ears: We used two transparent, plastic measuring-cups with red LEDs for the ears.

Main body bumps: The Cambridge pumpkin Dalek used plastic shot-glasses to light up. We needed something smaller and found plastic test-tubes on the web.

Gun and sucker: Sadly, our home plunger was too big. However, the whisk was perfect. We used a black lid and metal rod instead of the plunger.

 

Carving, Drilling and Testing

Making the LidLid Wiring

 

We cut off the top and scooped the seeds out. I imagine this part is similar to a real Dalek. We drilled holes for the wires to pass into the Dalek for the eye stalk and two ears. The stalk and ears push into the pumpkin flesh. Then we drilled twelve holes for the test-tubes and pushed them through. We also cut vents and an access hatch at the back.

 

Testing the LEDs

We soldered the yellow LEDs onto wires to hold them in place. They sit in the test tubes.

 

Testing the Servo

We used a separate power supply to power the servo. It took us ages to work out that we needed to join the negative terminal to the ground on the Pi! Once there, it also took us time to work out the slightly strange PWM on NodeRed - sending a "5" to the PWM output made it turn left 90 degrees - sending "15" made it turn right. Higher numbers just make the servo keep turning.

 

After much experimenting, we found some transparent plastic in the shed. We used this to fix the servo to the main body. We used wire staples to fix the servo rotor to the head.

 

Testing the PIR

We wanted to use a sensor to start the Dalek boot-up sequence automatically. The PIR worked very well connected to the same power supply as the servo (5V). We limited the number of messages to one per minute to prevent multiple signals travelling through the flow.

 

Writing the Flow

It took some time setting up the GPIO elements. Once these were done, LDR and Thermistor were skilled at sequencing adding delays and resetting at the end.

 

Sound

Sorting the sound took a bit of time. We found a kid's mini speaker with satisfyingly low sound quality. Works a treat. We downloaded various sfx mp3 files and transferred them across via terminal to the .node-red folder on the pi. Finally we made a new flow element by pasting this code into node-red:

 

[{"id":"65872231.9a78dc","type":"exec","command":"mplayer -really-quiet /home/pi/.node-red/dalek.mp3","addpay":false,"append":"","useSpawn":"","name":"EXTERMINATE!","x":1316.8081817626953,"y":245.25010299682617,"z":"ebd21660.142de8","wires":[[],[],[]]}]

We repeated this for a cool sfx boot up mp3 and robot shut down mp3 and added these to the flow. Sounds great.

 

Terrifying Small Children

Today is the 30th October. We will be tweeting the results tomorrow!


@BenRogersEdu

By LDR (9 years old) (+dad)

LDR logo

Introduction


In this game, you roll coins down a ramp onto a board with foil islands. When the coins make a bridge from one side to the other, it is a complete circuit and an LED lights up.

 

Version 1

Simple series circuit with LED. The coins make a conducting ‘bridge’ across the foil ‘islands.’


Version 1


First, I cut out the box and the foil islands. Then I stuck the islands onto the box and two rails along two opposite sides with glue. We made a circuit that made a LED light up and connected that to the rails with paper clips.

 

When coins made a “bridge” between the islands, the electricity flows and lets the LED light up. (We soaked the coins in vinegar to make them shiny and conduct well).

 

I made a ramp to roll the coins down out of cardboard and the game worked….

 

But not well enough!


Version 2 (writing the Node-Red)


We improved the game using a Raspberry Pi and Node-Red. I wanted a timer to make the game more exciting. We had a traffic light, so I used that by putting it straight onto the output pins of the Raspberry Pi.

 

We connected the two side rails to input pins on the Raspberry Pi so that it could tell if the coins had made the circuit complete.

 

I used a buzzer to tell you when the time was up.

 

I also used a switch to start the game. The green light went on for 20 seconds. Then the amber light came on for 20 seconds. Then the red light came on for 20 seconds. Finally, the buzzer went off.

 

If the coins made a bridge before the time was up, all of the LEDs flashed.

 

Node_Red Code

 

The Node Red code showing the start switch sequence and the ‘you won’ sequence.


Finally


The game is fun to make and fun to play. It is a good project because it teaches you how to programme a real game, not just on the screen.

 

Final Version

 

The full Node-Red version

 

 

LDR (9 years old)

Filter Blog

By date: By tag: