Quiz Game System

Bill of materials

Here’s what you’ll need to assemble your own Kamaji buttons. The quantities shown are per single button. Multiply that by the number you need and consder ordering some spares.

Everything (except the custom PCB) can be found on Aliexpress or other marketplaces for cheap.

Item How many Search query
Custom PCB 1 N/A
Cherry MX switch 1 cherry mx keyboard switch
2×3×4 square LED 1 2x3x4 square LED
M2.5 6mm bolt 1 M2.5 bolt 6mm
M2.5 threaded insert 1 M2.5 threaded insert
RJ10 (4P4C) socket 1 RJ10 socket
Translucent keycap 1 cherry mx keycap clear
Telephone cable 1 telephone cable 4p4c


For information on how to get the printed circuit boards manufactured, see next step.


The Kamaji button uses standard mechanical keyboard switches compatible with Cherry MX. You can buy original Cherry switches of your choice (e.g. blue, brown, black, red), or go for a compatible alternative from Kailh or Gateron.

One thing to check when ordering switches is whether they have a slot for an LED. The original Cherry switches do, but some clones might not have them.

We would not recommend saving pennies by going with no-name clone switches. The ones from respectable brands are cheap enough, and you only need one per player button.


The LEDs in the buttons are mounted into the slot of the keyboard switch. We recommend using 2×3×4 square LEDs, as they fit well. Other LEDs with the same lead spacing might work too. For more information see this thread on Geekhack.

Bolts and inserts

The enclosure parts and the PCB are held together with an M2.5 bolt and a threaded insert.

The bolt is a standard 6mm M2.5 bolt with a round head.

We used brass threaded inserts from CNC Kitchen. Other brands should work fine too, as long as they have similar dimensions (outer diameter 4.6mm, length 4mm). When ordering make sure to check the outer diameter of the inserts as it may vary significantly.

RJ10 Socket

Kamaji uses RJ-10 (4P4C) sockets that are commonly used for landline phones.

There are two things to look up for when ordering sockets:

  • Make sure you’re ordering 4-pin sockets, not 6-pin.
  • On Aliexpress and similar marketplaces there are two common types of sockets, one is narrower and the other is wider. Look for the narrow ones (~12mm wide).


You’ll need Cherry MX compatible keycaps. The keycaps should be translucent/clear so that it’s easier to see when the LED below is lit.


Now, with cables you have two options:

  1. Buy pre-made.
  2. Make your own.

The former is simpler, the latter is cheaper and more flexible.

If you’d like to buy pre-made cables, search for 4P4C telephone cables on Aliexpress or in local hardware stores.

For making your own cables you’ll need a crimping tool. Make sure it supports 4P4C plugs, not all tools do. Buy flat 4-wire telephone cable and 4P4C plugs and crimp cables of the desired length.

An added benefit of having a crimping tool and plugs is that you can repair broken cables by trimming and re-crimping them.


While you’re waiting for all parts to arrive, go ahead and order the PCBs.

Last updated on 14 Jan 2023
Published on 14 Jan 2023
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