What is it?

It is a PCB in the shape of a Christmas Tree with 12 charlie-plexed LEDs reverse mounted to shine through the board. The board is controlled by an Atinny13 and is powered by a Cr2032 coin cell battery.

Why did you make it?

I have long been an admirer of the amazing things people were making as part of #badgelife and wanted to try replicating some of the features seen in them. I thought the baubles would be a perfect candidate for the LEDs being reverse mounted. I also thought it would make a really interesting tree ornament for our Christmas tree!

What makes it special?

I think the reverse mounted LEDs shining through the PCB looks really great.

The PCB can be hung from a tree, it can free stand using the battery holder as a stand or be added to a badge using an SAO connector (4 pin).

You can select different modes for the LEDs using the built-in button. There is also a switch for turning off the power.

It can be fully modified/hacked using the AVR ISP pins. The base code can be found here

Running Modes

You can switch between running modes by holding down the button on the back. When you hold down the button (this might take a second or two) the animation will stop and a single LED will light up, keep holding the button and the single LED lit up will change. Each of the different LEDs represents a different mode.

The modes are: - Single LED flash (Speed 1-5) - Dual LED flash (Speed 1-5) - All LEDs on - ALL LED blink

What is in the kit?

• 1 PCB3 PCB
• 1 SMD Attiny13 (pre-programmed)
• 4 100 Ohm 0805 SMD resistors
• 1 Toggle Switch
• 1 Tactile Button
• 1 CR2032 Battery Holder
• 6 Red 0603 LEDs
• 5 Blue 0603 LEDs (NOTE: These are a little dim compared to others when running on the coin cell)
• 5 Green 0603 LEDs
• 3 Yellow 0603 LEDs
• 3 Orange 0603 LEDs
• 1 White 0603 LED (for the star)
• 1 String for hanging the PCB

Please note there are no batteries included (CR2032 required)

Add on options

• Colour - The colour of the PCB3
• Additional LEDs - This is different set of coloured LEDs that will be added to order (as well as the original LEDs that come with the kit)
• USB PCB Coin Cell - A way of powering the PCB3 from USB, see USB PCB Coin Cell Add-On section below for more details

Documentation

Additional information about the PCB3 can be found on my website

LED Layout

You will receive 5 different coloured LEDs: Red, Blue, Green, Yellow and Orange (And 1 white for the star) and there are 11 slots for the LEDs so you can arrange it however you would like!

Here is a suggestion for how to distribute the LEDs, it uses 4 of the available colours. Please note that blue is quite dim compared to the others (The main product image has blue at it's worse, the static mode). If this is a concern consider replacing blue with orange.

(Note the image is mirrored to represent the LEDs location on the back of the PCB, e.g. the red LED at the bottom left will be soldered on the back at the bottom left, but will be on the right of the board when looking from the front)

USB PCB Coin Cell Add-on

Please note that there are two version, a more square one than than imaged, when stock of the pictured one runs out I will be sending the square one. Functionally they are the exact same

New for 2019 is a USB PCB Coin Cell add-on. It is two PCBs designed to be the same dimensions as a coin cell battery with a micro USB connector so you can power the PCB3 directly from USB. These are assembled and ready to just insert into the PCB3 coin cell holder. What I like about this solution is you can swap between USB powered and battery powered whenever you need to.

There are two important to note about them: - They are not pretty! Small circular pcbs are quite difficult to clean the edges of the PCB of, they also look kind of scratched when inserted and removed from the coin cell holder (they come pre "scratched" as I have tested them) - These do not regulate the voltage to match a coin cell, the PCB3 can accept 5v. Do not assume you can use it with any other PCB without checking that it can accept 5v first.

Dave Darko

So this is kind of a strange section but I just wanted to thank Dave for his help getting the tree this far, my schematic and code was almost entirely based on his sloth badge and he was a big help with the reverse mounting LEDs which he demonstrated in his word clock project. I got all this information and inspiration with his permission in case anyone is wondering!

Soldering

Time: 30 mins. Additional Tools Required: Tweezers Difficulty: Medium - Most of the components are fine to install, the difficulty comes from the LEDs, not only are they 0603 sized, they are to be mounted upside down, which makes it a little bit more challenging. This was my first time soldering 0603 and I actually found the size no problem at all, keeping the LED level is where the difficulty comes. It ships with over double the LEDs need so there are some spares if required.

FAQ

• Will I get it before Christmas? - Please check An Post's dates for last posting (the "Standard Post Letters" option) to see if it will arrive in time for Christmas. Also please allow an extra day for me to ship it out! (so if the 10th of December is the final date, please order on the 9th or before!). Also be aware that sometimes Tindie manually reviews orders for verification, when this happens the order does not show up for me til the review is finished.
• Why are batteries not included? - There is shipping restrictions on batteries, so it's not worth the risk. You should be able to pick up these batteries (CR2032) cheaply in a dollar store. Ikea also sell an 8 pack of these batteries for €1.25
• How long does the battery last? - This is not a scientific answer, but roughly 24 hours. The code was still running after the 24 hours, but the blue LED no longer lit.
• Can I power it using something else? - Yes, I've tested with USB power it and it works fine. The Attiny should be fine up to 5.5V.