A2Relay

[!WARNING] This design is currently untested as of 5/26/2026. There may be errors in the design or example code.

Update 6/12/2026: Because the 74_259 resets to all outputs low and the relay module is active low, all the relays default to being on at startup. Adding a 74_240 inline between the 74_259 and relay board will correct for this in a future revision.

Schematics and Gerbers for an "OOPS! Inverter" board will be uploaded soon.

[!CAUTION] It is advisable to remove the VCC jumper on the relay board and power the relays with the GND and JD-VCC pin. The game port is designed to provide a maximum of 100ma, and with all relays turned on more than 500ma load will be present.

Apple II Gameport Relay Interface

This is a design for a small PCB to control inexpensive 8-relay modules ^{(Amazon affiliate link)} using the Apple II's gameport annunciators and strobe output. Use AN3 to set on/off state, AN0-AN2 to select which relay to control, and $C040 strobe to store the value. All pins are passed through to a socket where you can attach a gamepad, paddles, or other input device.

Applesoft BASIC Example

10 REM To turn on the first relay:
20 PEEK -16295 : REM Clear AN0 $C059
30 PEEK -16293 : REM Clear AN1 $C05B
40 PEEK -16291 : REM Clear AN2 $C05D
50 PEEK -16290 : REM  Set  AN3 $C05E
60 PEEK -16320 : REM Strobe    $C040

6502 ASM Example

0300  lda $C059 ; Clear AN0
0303  lda $C05B ; Clear AN1
0306  lda $C05D ; Clear AN2
0309  lda $C05E ;  Set  AN3
030c  lda $C040 ; Strobe
030f  rts