Tuesday, 6 December 2016

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.



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

Friday, 2 December 2016

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