Reading of a Three-Position Switch With One Digital Data Line
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
The reading of a three-position switch requires only one digital data line by employing a flip-flop. A three-position switch 1 is engaged with one of the contacts 2, 3, and 4. The contact 4 is connected to ground, the contact 3 is connected to +5 volts, and the contact 2 is connected to the Q output of a flip-flop 5, which may be a 74LS73 JK flip-flop, for example. The flip-flop 5 must be configured to operate in "toggle" mode. In the case of a "JK" variety, this consists of tying the J and K inputs high. The switch 1 is connected to a microprocessor, which may be an 8051 microprocessor, for example, through a tri-state buffer integrated circuit 6, which may be a 74LS125, for example, with a data line 7.