heartblink - a gift to my gf

a blinking {romantic} heart built with a bunch of leds and a Atmel ATTiny85 to rules them w/ charlie. Everything mounted on a home made pcb!

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Using charlieplexing techinque i will be able to drive 14 leds with 5 pin (actually 5 pin can drive 20 leds but my designed heart uses only 14).
I'm going to use things i found in my bedroom, i'm going to buy ($7) ferric chloride and a couple of copper pcb to create my own homemade pcb.

leds will blink sequentially using charlieplexing to make fun animation. This is a present for the 23 birthday of my gf!

Watching PCB schematic you can see blue wires, they will be air-wires.

Charlieplexing explained @

PCB making procedure @


  • 1 × Atmel ATTiny85
  • 14 × 3mm Red Led 20mA
  • 5 × 120Ohm resistors
  • 1 × 5v Battery
  • 1 × 10KOhm resistor

  • new old schematic + board

    mrbang0day08/06/2014 at 21:27 1 comment

    just completed the new old schematic using true pre-builded avr atmel attiny85 component, with a 10KOhm resistor between VCC and RST pin.

    this is the board:

    i'm going to print my own PCB using etching solution and marker for minor corrections. Blue dashed wires are air-wires!

  • i'm sorry, i can't get a cool design

    mrbang0day08/05/2014 at 18:50 0 comments

    i'm sorry, i tried to design cool schematic with everything inside the heart but seems to much harder for me at the moment. I'm a totally newbie on design and printing pcb. I'm going for standard layout with resistor and ATTiny outside the heart

  • shopping

    mrbang0day07/26/2014 at 13:10 0 comments

    pcb copper, ferric clorhide, marker and leds will be come at home on tuesday, total spending 7 Euro + 3 Euro for shipping costs! yay!

  • draw new schematic

    mrbang0day07/26/2014 at 13:03 0 comments

    Thanks to davedarko i managed to draw a new schematic, now ATTiny is placed in the center of the heart. Pin wirings were corrected and i put a 1Kohm R between RESET pin and VCC (give me some feedback, it is correct?)

  • start to design it

    mrbang0day07/25/2014 at 15:40 0 comments

    i'm a newbie on designing schematics for my projects but i'm going to do my best! thanks to a commet here below i'm going to:

    1- fix the wrong wiring on the reset pin of the attiny85

    2- edit the pcb design to wrap attiny85 with red leds all around!

View all 5 project logs

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mrbang0day wrote 02/20/2015 at 23:24 point

i didn't complete it! i committed various mistakes during pcb etching procedure and i gave up!! actually if someone can share any tip about how to print design and impress it onto the pcb i will be so glad..

  Are you sure? yes | no

davedarko wrote 02/20/2015 at 23:54 point

Can you post some pictures of your failed attempts? That could give away some points may be. Drawing it by hand sounds hard, since you have to mirror it etc. 

It's better if you use the bottom layer (blue) for your board, since it will be on the bottom later. 

  Are you sure? yes | no

mrbang0day wrote 02/20/2015 at 23:57 point

i printed the design using a laser printer onto some plastic gross paper.. then i transferred the image onto the pcb using an iron.. but lines was not so marked

  Are you sure? yes | no

davedarko wrote 02/21/2015 at 00:02 point

I've bought a laminating machine once I saw a cheap one. Using an iron you have to hold and press it really long and make sure that you really really heat it well. Were you able to use the markers to fill the lines? How did your printing file look?

  Are you sure? yes | no

davedarko wrote 02/21/2015 at 08:22 point

Something in the way like this. Do you have a 10cm*8cm copper board? You would then have to print this normal and etch it. I took your design and couldn't resist doing it the way I mentioned before, placing the attiny inside and placing the LEDs so they all face the same direction. I've used the blue layer and finally exported a picture of it and the via layers in monochrome. You would have to etch it and drill the holes and put the parts in. 

By the way, have you tested your circuit on a breadboard before or have the software ready?

  Are you sure? yes | no

Dmitry Grinberg wrote 02/18/2015 at 00:30 point

I made one like this for v-day. Used 20 LEDs and wrote firmware to actualy allows 8-bit brightness on each simultaneously. I can share the code with you if you'd like.

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Stefan-Xp wrote 09/24/2014 at 18:39 point
Have vou completed in time?
Hope everything went well ;)

Best regards,

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davedarko wrote 10/25/2014 at 10:31 point
I wondered that, too. Maybe this comment got lost in the previous faulty feed version of ...

So how are things, mrbang0day? DO you need any help?

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Stefan-Xp wrote 08/10/2014 at 08:45 point
Nice new Design! :)
But three issues which could be considered.
- Perhapps you could try to avoid 90° traces.
- Perhapps you could consider to use "silver wire" instead of "air Wire" would look nicer (You would just have to add a via more per trace, also try to avoid angles at the air wires)
- Perhapps you could "bend" the circuit board at the point of the resistors to save space.
Keep on the good work :-) best regards, Stefan

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davedarko wrote 08/05/2014 at 19:09 point
Don't feel bad! My quote for failed board design vs. good board design is 4:5 right now :D I have a thing for over killing and over thinking stuff. Since your on a schedule it is good to know that you have to pull the break and focus on the next steps :)

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mrbang0day wrote 08/05/2014 at 19:30 point
glad to get your support!! :)

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davedarko wrote 07/26/2014 at 13:23 point
Since the comments on logs don't show in your feed I'm going to post here...

I have read that you should choose a resistor higher than at least 4.7kOhm and typically around 10kOhm for the reset pin or otherwise the programmer can't pull it down properly. But that should not be a dramatically thing to change.

A little tip for the LEDs, try to put them facing the same direction - like "anode up". This way you just have to grab the LED and keep in mind to put the long leg in the upper hole. It's embarrassing to say but I always mix that up with LEDs... and since your self-made boards won't have a stencil on it with the dent printed on telling you where to put the dent of the LED you would have to check every LED you place for the right orientation. If you don't mind the german, this is my LED cheat sheet:

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davedarko wrote 07/26/2014 at 13:27 point
I almost forgot, how will you program it?

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mrbang0day wrote 07/27/2014 at 12:43 point
thank you for you tips!! yes, the Resistor for the reset pin is 10Kohm actually on the schematics i wrote 1Kohm but near schematics info (bottom right) i wrote 10Kohm! I will study how to design it putting all leds facing the same direction! I'm going to program the ATTiny85 via my own Arduino 2009, i do not have atmel programmer! i will code in C, i will share my code asap so you can take a look on it!

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davedarko wrote 07/27/2014 at 14:07 point
Feels good to help :) You also wrote in your log you would use a 1kOhm ;) I guess you noticed it already, but you can change the values of your resistors in the schematics by selecting the and then click on the resistor, just for documentation. If you think you have to probably reprogram it onboard - an ISP header, extra pinheaders (connected before the resistors) next to your chip or a DIP IC socket would be helpful, too.

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Stefan-Xp wrote 07/25/2014 at 15:13 point
First off, i like the idea, i also thought about something like this ;-)
But I would have gone for SMD parts ;-)
BTW: If you only creating one piece, you could also consider painting the PCB by hand with a marker ;-) (you could use a ruler or something ;))

I'm looking forward for the outcome of your project ;-)

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mrbang0day wrote 07/25/2014 at 15:38 point
thank you for your tips of using marker! i'm going for it probably!!

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davedarko wrote 07/25/2014 at 10:49 point
First off, I love charlie-plexing :) Any reason you are using the reset pin instead of the 5th IO pin of the attiny? would be cool to see a heart-shaped board where the LEDs are all around the attiny85.

  Are you sure? yes | no

mrbang0day wrote 07/25/2014 at 15:37 point
thank you, sorry probably i did some mistake during pcb designing using Eagle (first time i used it was yesterday) i'm going to fix the design tonight!! thanks for the amazing idea of a heart shaped board with leds all around attiny85

  Are you sure? yes | no

davedarko wrote 07/25/2014 at 16:38 point
no problem :) I'm still trying to get around with eagle, too. Google helped me a lot though. I made a board with the attiny once and that pin is the same on the atmegaX8s (1=RST) so I instantly saw that ;) Good luck with it :)

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