USB rotary channel changer: Hardware

Architecture

At first I listed up some requirements for this product.

1. It must have 12 channels at least.
2. Avoid difficult or troublesome manufactures.
3. Does not require any device driver development.

I considered to use a parallel port but my laptop has no parallel port on it, so I threw away that idea. Then, I got an idea that I could use a USB joypad.

Fortunately, recent joypads has a number of buttons, it was able to put 12 channels and easy to develop, just soldering a rotary switch to a chip of the joypad. Besides a generic USB joypad driver is enough.

Parts list

Item	Model #	Price (Yen)
12 points rotary switch	SRN101C	260
12 buttons USB joypad	JC-U812	1280
Case	TS-1	670
Knob	---	160

Rotary switch I used is made by ALPS. I didn't care the type of shorting, because I didn't know what the meaning of "shorting" at that time, to be honest.

The joypad. It has 2 axis and 12 buttons, so it can handle 16 points at most.

Assembling

Assembling process was very simple.

1. disassemble the joypad.
2. unsolder the USB cable from the board.
3. solder 13 wires to the board.
4. solder the rotary switch.
5. make 3 holes on the case.
6. assemble them. (solder the USB cable again.)
7. decal some numbers, if you like.

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Solder the wires. In this picture the wires were soldered to the switch, but I recommend you to solder all of the wires to the board at first, then solder to the switch.

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Like a mangrove. You'll be confused during this process.

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There are 3 holes on the case. There is a small hall nearby the hole for the main shaft of the rotary switch. The switch has a small dip beside the shaft to hold itself.

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Put the board and the switch into it.

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Almost finished.

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Decal the numbers. This lettering sheet is not so tough. It would be better to coat them.

Next chapter: Software