Table of Contents
Rotary Joysticks
Rotary joysticks aren't common, but this is probably the most common mechanism. It's a 12 position rotary switch mounted to the base of the shaft of a joystick. In Japan they are usually Seimitsu, but in the West there are a lot of Wico sticks in use.
This page is, at least for now, primarily about the Wico variant. They are compatible, though the pinouts differ.
Like most controllers the active position is electrically low, ie: connected to ground. The game board holds each signal high, and detects the change when the active position is connected to ground.
The Wico rotary mechanism uses a small PCB with a C&K SP12T rotary switch doing the selecting. The PCB has a few extra components on it: two diodes, a small resistor array and a 74HC03 IC. It took me a while to get my head around it, but they are used to prevent positions 3 & 4 from being simultaneously activated. It seems that the switch is built in a way that sometimes allows this to happen.
The PCB can be mounted to the base of any appropriate shaft. This particular one has a hollow base with a small hole. The handle of the switch is inserted into the hollow shaft and a small grub screw locks it in place.
Pictures
Pinout
Rotary Switch PCB
| Rotary Pin | Signal | Rotary Pin | Signal |
|---|---|---|---|
| 1 | Pos 5 | 8 | Pos 11 |
| 2 | Pos 6 | 9 | Pos 12 |
| 3 | Pos 7 | 10 | Pos 1 |
| 4 | Pos 8 | 11 | Pos 2 |
| 5 | Pos 9 | 12 | Pos 3 |
| 6 | GND | 13 | Pos 4 |
| 7 | Pos 10 | ||
Note: The pins are numbered on the plugs.
Rotary Board to Game Cable
The cable is not complicated, and mostly follows a sequence: 6-1, 13-9. Two pins are swapped, watch for it!
| Rotary | Game PCB | Rotary | Game PCB |
|---|---|---|---|
| 1 | 6 | 8 | 12 |
| 2 | 5 | 9 | 11 |
| 3 | 4 | 10 | 10 |
| 4 | 3 | 11 | 9 |
| 5 | 2 | 12 | 7 |
| 6 | 1 | 13 | 8 |
| 7 | 13 | ||
Note: The pins are numbered on the plugs.
Part Numbers
The connectors are made by Panduit, but the part numbers are not known.
Schematic
The schematic shown here is clever. The two diodes take the very low 5V from the game board and power the chip with it. By drawing power from both positions 5 and 7 it ensures that there's never a time when power will be unavailable.
The four NAND gates in the 7403 IC will only output a low signal if both inputs are high. The 680k array provides a high signal to one input of every gate, switch positions 3 and 4 provide the other inputs.
By using four gates this way both positions 3 and 4 will, when active, prevent the other from also being active. The only way either of them will return an active (low) signal is if the other one is unselected (high).
