Thursday, November 12, 2015

Codebug - Flashing LED tree made with conductive paint

Last year I made some conductive paint using this Instructable.  For me 50:25 by weight, paint to graphite powder works great. Make sure to stir in slowly otherwise the graphite powder will fly.
With this mix the paint is easy to apply yet has good conductivity.
It worked great and I used it at a Raspberry Jam to make flashing LED eyes for Halloween.

Since then the paint has been abandoned until my eldest daughter mentioned she was making circuits in school yesterday and I said I'd try to make them flashing LED Christmas Tree pictures.
This got a thumbs up from my daughters so the pressure was on.

Using Inkscape I drew a simple Christmas Tree with a place to put 7 LEDs.
Nice and simple and easy to print on A4 card.  I made the baubles the shape of a physical LED so you can see which way to place the LEDs on the sheet. All the negative (ground, cathode) sides in the middle making it easier to connect all to GND later.
PNG Version.
Links to PDF and SVG 

With the drawing done I added the LEDs.  6 to the green tips and a yellow one in the star.  I had 2mm LEDs to hand so that's what I used.  For the real thing I plan to use 5mm as the effect should be better.

I found pre-bending the LED leads at right angles so they are pointing down when in places made it easier to  get the LED to stand up at the front.  I also made small holes using a pin to push the LED leads through.  It's hard to push LEDs through 300gsm card as the leads don't have a point.

Once this was done I turned over the card.  Left the ground side for each LED pointing down and turned the positive side (anode) out at right angles pointing to the edge.  Once done I used a small piece of tape to keep the LEDs in place.
Tip.  Push the leads down to they push against the card. It's means the leads lie flat making them easier to hold on with just paint.

Back of the card
As I mentioned the conductive paint had spent the last year drying so was a bit sticky meaning the paint job is less than smooth.  I have since revived the paint with a little bit of water so for the kids it should be much easier to paint.

The bar down the middle is the ground tied to all the LEDs.  The other lines are for the positive side of each LED.
If you want all wires to be at the bottom then you may have to adjust the SVG in Inkscape to only print one Tree per A4 landscape card.

To test I thought I'd use a Codebug I got in the Kickstarter and hardly used it since. They are no on sale at CPC Farnell
With the help of Twitter people (I didn't declare the legs as outputs at the top of my code) I put together the following program. Link to CodeBug site for project

CodeBug code
Once all this was done the LEDs flashed. Yeah!.

For this project I wired up the LEDs so the top and bottom on one side are paired with the middle one on the other side and vice versa and the star LED on a leg of it's own.
This only uses three  (3) legs on the CodeBug,s o the 4th one (3) in the code is redundant.  I just left it in there in case I can figure out a more exciting way to use 4 outputs to flash 7 LEDs.

Very Short video of the final tree.

Next I want to wire up to a Raspberry Pi to enable interactive input and independent control of all the LEDs and maybe play a Christmas tune as well.

Sidenote; Some might be asking where the current limiting resistor is.  It's the paint.  The conductive paint has a higher resistance than wire and so it is acting like the current limiting resistor.

Friday, October 9, 2015

9th Egham Jam – Show and Tell Competition – Prizes donated by 4tronixs

I think we might be coming to the end of the Prize announcements.
So, last but not least are the Prizes donated by 4tronixs.

Robot lovers Prizes from 4tronixs

These prizes are especially situated to the robots lovers.

Each Prize includes:

The PlayHat includes a 3x3 full colour neopixel LED matrix, 4 big buttons and a buzzer.
Great for programming with the Raspberry Pi. This is just begging out for a game of Simon to be created.

PiRoCon and iBoost64 This board is great. Te PiRoCon  plugs right on top of the Raspberry P and gives you all the additional electronics needs to drive motors.
Motors are fun things. When they start they draw a lot of  power (think of train pulling out of the station. It needs far more power to get going then it does to keep itself moving.  Same thing for motors).  This mean if you want to drive motors you need extra circuitry to do it safely without damaging your Raspberry Pi.  The PiRoCon is one of the best solutions for this for the Raspberry Pi.

In addition to motors drawing a lot of power when they start and stop they can also affect the voltage and current of electronics drawing from the same power supply.  This can cause difficulties in getting good readings or accurate control.  This is where the iBoost64 comes in.  It cleans up the signals and makes them good without affecting the rest of the circuit.  Ideal for robots where there can be a lot of stopping and starting of motors as well as reading of external sensors for line following or object avoidance.

With the combination of the PiRoCon and iBoost64 you have the electronics to get that robot built.
If working in Scratch the current ScratchGPIO library from Simon Walters supports the PiRoCon.

If you have robots you will need power.  The final 2 boards are a 1 way and 4 way charger board for Li-Po batteries.  These are great batteries for robotic as they store lots of energy and give out a consistent voltage.  Cheap batteries have a power curve that means they very quickly drop from the maximum voltage which can cause lots of problems with motors.  Li-Po batteries are the ones used in high quality remote control cars.
Unfortunately you can't just plug a Li-Po battery into your normal battery charger due to the way they work so custom chargers are usually provided or need to be purchased with the battery.  These great little boards mean you can use a standard 5V microUSB power supply to charge the batteries.  This is the same type of power supply used for the Raspberry Pi, meaning if you are building a Raspberry Pi based robot you will already have the correct power supply.
There are 2 different boards included.  A 1 way, so it can charge 1 battery and a 4 way which can change 4 batteries at the same time.  Giving you more than enough power for your laser guided, GPS tracking, missile shooting, web cam streaming, grabber, digger, flame thrower robot. Or maybe just a line following robot.

From the picture you can see they also provided some pens.

Thank you 4tronixs for the prizes.

Thursday, October 8, 2015

9th Egham Jam – Show and Tell Competition – Prizes donated by RasP.IO

With the Egham Jam on this Sunday ( it's lovely to be see the prizes are still coming in.

This time from RasP,IO who product a number of really useful and practical accessories for the Raspberry Pi.

RasP.IO Breakout / 40 pin portsplus2/26 pin ports

The Ports boards are 26 and 40 pin versions so perfect fit for both types of Raspberry Pi.

The Breakout gives you easier access to the GPIO pins and allows you to use male/male jumper wires just like Arduino, so ideal if you're like me and have a load of these already and very few male/female jumper wires. It also gives the same labeling as per the original RasP.IO ports boards. The current model available is the 26 pin version which will fit on the 40 pin B+/2.

In addition RasP.IO ran a Kickstarter for their gpioruler for the B+/2 40 pin Raspberry Pi. I supported the 4 ruler pledge and will be providing one for each prize pack.

GPIO Ruler

+Alex Eames the man behind RasP.IO has also done some fantastic videos on the Raspberry Pi that you see at

Here's looking forward to a fantastic event.
See previous posts for other prizes for Sunday.