CamJam December 2016

On Saturday 3rd December  I travelled up to Cambridge to attend another excellent CamJam.  I had a good look around the market place as well as some of the show and tell items.

Trevor Olsson had brought along his latest project. A full size traffic light complete with a pedestrian crossing signal and button.  The traffic light and pedestrian button were connected to a gPiO control box with a simple Scratch program running on Raspberry Pi.

Tony Goodhew had some interesting projects on display, one showing how charlieplexing worked and one called a bigger project.  This had two Raspberry Pi's connected together wirelessly using the NRF24L wireless modules allowing one to control the other.   The first Raspberry Pi had Blinkt! HAT with some Python software which allowed you to change the colours, this was transmitted wirelessly to the second Raspberry Pi which had a Sense HAT showing the colours and a numeric display. 



David Saul had a nice collection of his recent Kickstarter Tempus Fugit WordClock and a Twitter controlled Christmas jumper.



Steve Upton had a large scale LED wall, made using strips of Neopixels. It was running Space Invaders and had some scrolling graphics.



Jonathan Pallant had a rather nice project called Xmas Pi, it was controlled by a Raspberry Pi and used some Neopixels.




Phil Willis had Fritz and a couple of robots on display.





Workshops

I helped out with the SenseHAT workshop.  The attendees got to learn about the Raspberry Pi and Sense HAT and do some Python programming.

Electronic Christmas Decoration

And now for something completely different…

While perusing the Christmas tat in Poundland /Poundworld recently, I found some cheap battery powered Christmas lights and thought I could hack these.  

I chose some LED Christmas trees, stars lights and multi-coloured lights. These take 3v in the form of 2 x AA batteries, but you can snip the battery holder of and connect them to your Raspberry Pi or micro:bit.

The first thing I did was to snip the battery holders off and connect them to my Raspberry Pi, I used some driver transistors to protect the Raspberry Pi’s GPIO ports. I wrote a simple Python script using the excellent GPIO Zero library to flash the lights on and off.  This worked well but I had seen a simple Christmas decoration project in an old book called Digital Electronic Projects for beginners by Owen Bishop. 

Lights connected to my Raspberry Pi

I thought I would build the circuit to see how well it worked.   The project uses a 555 timer and CD4040BE 12-stage binary ripple counter to make a set of 5 LED’s light up according to the binary sequence with some additional add-on extension ideas.  I modified the circuit and replaced the CD4040BE with a CD4042BE 7-stage binary ripple counter as I didn’t need all of those stages.  I added a UM66T-01L which is a melody generator IC and plays ‘Jingle Bells, ‘Santa Claus is coming to town’ and ‘We wish you a Merry Christmas’.  Finally I added driver transistors to drive the LED strings as the CD4024BE can’t supply a lot of current via the outputs. 

Prototyping the circuit

Prototyping the circuit

I was happy with the circuit so I transferred it from the breadboard onto some stripboard. Overall I'm very pleased with how it worked out and there's not a single microprocessor in sight.

Final circuit built on stripboard

Final circuit schematic

Micro Operation

Take one classic Operation game and connect a BBC micro:bit to it, what could be more fun.  Having seen a similar project I thought I would have a go myself, so I had a quick browse on eBay and found one cheap. 

A few days later the game turned up and it appeared to be in good condition.  I removed the existing black box containing the electronics, the batteries had corroded but luckily only the battery connections had been damaged. I took everything out and connected some new wires to the tweezers and connection to the metal plate.  I also replaced the existing LED.

Existing electronics, somewhat crusty.

Existing electronics removed and new wires connected.

I connected the new wires up to the GPIO pins on the BBC micro:bit and tried out the awesome code written by David Whale.  I used my new Proto-pic exhi:bit Prototyping system for micro:bit but the Kitronik prototyping system would work just as well.  The game was fun to play and had some awesome animations. After 3 operations, if you are successful in the operation time limit, the man jumps out of the bed and walks away.

BBC micro:bit Edge Connector	Operation game connections
P0 pin	Tweezers, active high
P1 pin	Nose LED via series resistor
P2 pin	Speaker, other pin to GND
+3V	Internal metal plate

You will need:

1 x Operation game

1 x BBC Micro:bit
1 x 5mm Red LED
1 x Suitable resistor for your LED (I used a 47Ω)

Connecting wires

1 x speaker or piezo

The code was written by David Whale and can be found below.

A simple version of the game can be found  here  

Full version of the game can be found  here

Teleporting Ducks

The excellent Python MU editor makes it so easy to get BBC micro:bits talking to each other using simple radio data communication. No magic required, just physics.

After attending a brilliant talk / demo about the MU editor by Nicholas Tollervey, I came away feeling inspired.  I thought I would have a go myself and in no time I had 2 microbits sending data to each other wirelessly.   

I wrote some simple code based on an example by Nicholas Tollervey. First to send an image when pressing button ‘A’ between micro:bits.

1. from microbit import display, button_a, Image
2. import radio
3. radio.on()
4. while True:
5.     message = radio.receive()
6.     if message:
7.         display.show(Image.DUCK)
8.     if button_a.was_pressed():
9.         display.clear()
10.         radio.send("hello")

I present my magical teleporting duck, prepare to be amazed. #bbcmicrobit pic.twitter.com/9CG0CkhYdw

— Thomas Stratford (@MrTomsWorld) 26 October 2016

Next I thought it would be fun to add some neopixels. When button A is pressed the neopixels show red then amber on the sending microbit and green plus the image on the receiving microbit.

1. from microbit import *
2. import radio
3. import neopixel
4. np = neopixel.NeoPixel(pin0, 1)
6. green = (0, 255, 0)
7. red = (255, 0, 0)
8. orange = (255, 153, 0)
10. radio.on()
11. while True:
12.     # Read any incoming messages.
13.     message = radio.receive()
14.     if message:
15.         np[0] = (green)
16.         np.show()
17.         display.show(Image.DUCK)
18.         sleep(3000)
19.         np.clear()
20.     # Button A sends a "flash" message.
21.     if button_a.was_pressed():
22.         np [0] = (red)
23.         np.show()
24.         sleep(1000)
25.         np [0] = (orange)
26.         np.show()
27.         sleep(1000)
28.         np.clear()
29.         display.clear()
30.         radio.send("hello")

New and improved magical teleporting duck, complete with neopixels... #microbit #bbcmicrobit pic.twitter.com/PHqdaML9qD

— Thomas Stratford (@MrTomsWorld) 27 October 2016

To connect the neopixels you’ll need to attach them to the micro:bit as below.

You will need:

2 x  BBC micro:bits

2 x Neopixels ( I used Crumble Sparkles )

6 x Crocodile leads

The code is available here.

12th Egham Raspberry Jam

On Sunday 16^th October I travelled down Egham to attend the 12th Egham Raspberry Jam, it's my first time I have attended this particular jam.  It was held at the Gartner UK HQ offices, which was easy to find and had plenty of parking. There were plenty of cool show and tell projects to look at, but no workshops or talks.  

I took a couple of BBC micro:bit projects and my Raspberry Pi trick or treat detector project along. I spent most of my time talking to people about my projects, however I did manage to have a look at the other projects on show.


My Show n Tell projects.

Nevil Hunt had several nice BBC micro:bit projects on display.



A nice haunted house.



Raspberry Pi machine which dispensed pancakes complete with jam.




Acorn electron with Raspberry Pi and Arduino inside.



Matt Sendorek's Raspberry Pi controlled Maplin robot arm.



Carl Monk's Breakout Clone.




Some more pictures can be found on my Flickr page.

Trick or Treat Detector

Detect those pesky kids before they get to the front door. Put it outside to spook the Trick-or Treaters as they walk up to your door. This project is motion activated using a PIR sensor, upon activating the Owl and some cheap LED string lights turn on.

Step 1.  Prototyping

I built the circuit on a breadboard to test the idea. I used the PIR sensor and breadboard from the brilliant CamJam EduKit 2.  I used transistors to drive the LED’s as the Raspberry Pi GPIO pins cannot supply a lot of current. The code was written in Python using the great GPIO Zero API.  I set the Python script to load on start-up.

Breadboard layout

GPIO Connections

GPIO 4 -  PIR sensor
GPIO 5 - Owl via driver transistor
GPIO 6 - Bat lights  via driver transistor
GPIO 12 - Hand lights via driver transistor
GPIO 17 - Shutdown switch


Step 2.  Transferring the circuit onto a PCB

The circuit worked well so I decided to transfer the breadboard prototype onto a more permanent Adafruit Perma-Proto HAT.   

Step 3. Building into an enclosure

While looking for suitable enclosures in Poundland I came across a nice plastic pot full of Halloween sweets, having removed the sweets to eat later.  I set about cutting some holes in the pot for the PIR sensor and 3.5mm mono jacks.   I connected all of the cables and checked that it worked. 

Parts List:

1 x  Raspberry Pi board, any model will work

1 x  Adafruit Perma-Proto HAT for Pi Mini Kit - No EEPROM 

3 x  NPN Transistors

3 x 10KΩ Resistors

3 x Suitable resistors for the LED’s ( I used 22Ω resistors)

1 x PIR Infrared Motion Sensor (HC-SR501)

1 x PCB tactile switch

3 x 2 way Molex KK type 2.54mm headers and housing

1 x 3 way Molex KK type 2.54mm headers and 2 housings

Some cheap Halloween lights from Poundland

Complete code listing:

1. from gpiozero import *
2. from subprocess import check_call
3. from signal import pause
4. import time
7. pir = MotionSensor(4)
8. owl = LED(5)
9. bat = LED(6)
10. hand = LED(12)
13. owl.off()
14. bat.off()
15. hand.off()
18. print("waiting for pir to settle")
20. pir.wait_for_no_motion()
23. while True:
24.     print("ready")
25.     pir.wait_for_motion()
26.     print("motion detected")
27.     owl.on()
28.     bat.blink()
29.     hand.blink(2,2)
30.     time.sleep(30)
31.     owl.off()
32.     bat.off()
33.     hand.off()
35.     def shutdown():
36.         check_call(['sudo', 'poweroff'])
38.     shutdown_btn = Button(17, hold_time=2)
39.     shutdown_btn.when_held = shutdown