Description: Apple III: Game Paddles
Header: Apple III: Game Paddles


 This article last reviewed: 21 September 1984

 Standard Apple II 150K game paddles cannot be used with the Apple III.  A high
 impedance potentiometer like the Apple II paddle will not work properly
 connected to an Apple III port.

 The analog inputs on Port A and Port B of the Apple III are designed to read a
 voltage between 0 and 2.4 volts and convert it to a number between 0 and 255.
 The schematic on page 82 of the Apple III Owner's Guide is drawn for a
 joystick with 5,000 ohm potentiometers.  Only the bottom 20% of the
 potentiometer's range is used.  Using the +12 volt power supply will result in
 the most stable readings.

 The following circuit can be used if the entire range of the potentiometer is
 desired.

               +12 or +5 volts
                      |
                      |
                      <
                      <  Rs
                      <
                      |
                      | <------ must be 2.4 volts at this point.
                      |
                      <
         GC input ---><   Rp  (1 - 2K ohms)
                      <
                      |
                      |
         0 volts  ____|

 The voltage range at the GC inputs should go from 0v to 2.4v. The value of Rs
 can be calculated for +5 volt systems with this formula:

        Rs = Rp * 2.6 / 2.4

 For +12 volt systems use

        Rs = Rp * 9.6 / 2.4
 1988


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