Cordwood puzzle too

A second in a series of
cordwood puzzles

Saving space back in the day. Source

The completed project

The completed project

Comes in a lovely bag

Our first Cordwood Puzzle was very much loved, so we created a second in the series.

In the 1950s and 1960s inventive engineers saved space by using the 'cordwood' assembly, where components were sandwiched in between two circuits boards. This construction became less useful with reduced component sizes, PCB manufacturing advances, more compact integration, and surface mount technology, but is still a lovely piece of history. Combining both old and new, the Cordwood Puzzle is a tribute to this construction and to the engineers who came up with it.

The puzzle is to correctly assemble the circuit with the components at hand. Once completed, all LEDs light up when power is applied. When connected to a controller board each LED can be individually controlled.

Kit content

Kit content

Unfortunately(!), all the comprehensive assembly guides were mysteriously missing from the kits.

The Cordwood Puzzle can be connected to a controller board (like an Arduino) to control each LED

The Cordwood Puzzle can be connected to a controller board (like an Arduino) to control each LED

The kit contains

  • x8 10KΩ 2W resistor, Multicomp MCMF02WJJ103A10
  • x8 220Ω 2W resistor, Multicomp MCF 2W 220R
  • x1 1uF ceramic capacitor, AVX SA305E105MAR
  • x8 n-channel MOSFET transistor, Fairchild 2N7000
  • x1 10-pin through-hole header, Multicomp MC34739
  • x4 10mm yellow LED, Kingbright L-813YD
  • x4 10mm green LED, Kingbright L-813GD
  • x1 25mm M3 standoff, ETTINGER 05.03.251
  • x2 M3 screws
  • x2 PCBs
  • Piece of 0.84mm diameter 20AWG hookup wire

Further information

Cordwood Puzzle Too is an open source design, as is most of our work. You can find the design files for the hardware and packaging at our GitHub repository. You can edit the design files using our own PCB design open source software, PCBmodE.

Cordwood Puzzle Too was Project #13 of the Boldport Club. If you'd like to purchase a kit, become a member and add one to your order through the shop.

The PCBs were lovingly made by Eurocircuits.

Thanks to Erbsland Art for taking lovely picture of the project. Full album is here.

Finally, community contributions for this project are on our community site.



Challenge yourself by assembling the kit without further instruction. Before you do that, however, note the following: When connecting to a board, make sure that the I/Os can tolerate the voltage levels that are applied to the Cordwood! Also, make sure that you do not short power and ground!

Keeping with the theme a puzzle we do not supply full assembly instructions. Below is a reference gallery of the completed article. The board itself has assembly hints; can you find them? Finally, the assembly instructions for the first Cordwood Puzzle could be helpful ;)