HeartBoard Update!

The Project:


A new lesson in small run board production. So after the first version of the Heartboard kit I designed back in 2009, a couple of changes were stongly requested. The most sought after was an on-off switch, to turn the original board on or off you needed to remove the coin cell battery. The second was the switch to all 0805 (surface mount size) components from the mix of 0805 and 0603(a smaller surface mount size). Not a lot of people were happy with soldering the 18 0603 resistors for the LEDs around the outside of the board. And finally a new comprehensive instruction manual was written with pictures.

Design Constraints

  • Ease of construction – It should not be impossible for someone who has never surface mount soldered to finish the board in a reasonable time ~1 hour.
  • Cost – The goal was a low cost intro to surface mount soldering and something that could be given out on valentines days by engineering students.
  • Timeline – Finish boards before valentine’s day!

My Role

  • Circuit design – Specify parts and develop low cost circuits .
  • Board design – Creating the shape of the board and the layout of components.
  • Procurement Specialist – Buy all the parts in bulk and find/deal with the board house located in china.
  • Lead Coder – Pretend you have minions to boss around while writing all code for the microcontroller.
  • Assembly Manual Creator – Create an easy to understand step by step instruction manual (Thanks to Danny Vacar for the help!).

Lessons Learned

  • PIC16F57 Architecture – 3KB of program memory is really really small :( Also a 2 layer stack pointer means that the third nested function you call blows everything up and makes debugging a nightmare.
  • Instruction Manual Creation – Creating an instruction manual that will allow anyone to assemble a board is a long process.  It is hard to place yourself in the clients shoes. I feel for all the bloggers and documentation writers who create in depth write ups of their projects.
  • People love switches – No matter who they are everyone seems to love playing with either the slide switch on the back or the pushbutton switch on the front.
  • Component Prices Change – These seems obvious but the cheapest components found on digikey two years ago may 1. go up in price for what seems like no reason. or 2. be replaced with a cheaper alternative.
  • Advertising – The circuit board has had huge success with students staff and faculty, but people only find out about it via word of mouth.
  • Experimentation – The resistors and capacitors that make up the RC circuit to power oscillator for the microchip can and will be played with by people that make them both intentionally and accidentally “why is my board running so fast?”.
  • Surface mount soldering – Even if you make someone’s life easy with Surface mount soldering someone will still want the board with all through hole components.
  • Pre assembling more then 15 – Buy a stencil, It will make your life so much easier.


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