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Project Notes

#321 cordwood-too

The Cordwood Puzzle returns! Boldport Club Project #13, May 2017



The original Cordwood Puzzle became an instant classic with club members, and the concept returns this year with a brand new puzzle. The cordwoods evoke an era of stuffing massive components into small spaces. This is real hardware!

As before, it really is a puzzle, so if you don’t want any spoilers - read no further.

Unboxing and Parts Count


Ref Part Qty
R2,4,6,8,10,12,14,16 10KΩ 2W resistor, Multicomp MCMF02WJJ103A10 8
R1,3,5,7,9,11,13,15 220Ω 2W resistor, Multicomp MCF 2W 220R 8
C1 1uF ceramic capacitor, AVX SA305E105MAR 1
Q1-8 n-channel MOSFET transistor, Fairchild 2N7000 8
  10-pin through-hole header, Multicomp MC34739 1
  10mm yellow LED, Kingbright L-813YD 4
  10mm green LED, Kingbright L-813GD 4
  25mm M3 standoff, ETTINGER 05.03.251 1
  M3 screws 2
  PCBs 2
  Piece of 0.84mm diameter 20AWG hookup wire 1



The LEDs are rated for 20 mA with forward voltage of 2.V (yellow) and 2.2V (green). Therefore, with the current-limiting resistor of 220Ω, the maximum supply voltage is around 6.5V.

How It Works

Each LED is switched by a corresponding MOSFET. The MOSFET gate is pulled high by default with a 10kΩ resistor, so the defualt LED state is ON.

Each gate is also connected to a pin. If these are pulled to ground, the corresponding LED turns off.




With it’s twin, the original Cordwood..


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.