| 摘要 |
PURPOSE:To make a switch connectable independently of normally open or normally closed type switch, to simplify the external connection even with lots of sensors and to make the cost low by constituting a switch matrix circuit by resistors and diodes. CONSTITUTION:When external sensors (normally closed type switches) S1-S16 are all closed, an output port O1 goes to ''H'' level, a transistor (TR1) is driven and a point A is brought into ''H'' level. On the other hand, TR2-TR4 are turned off and at ''L'' level because output ports O2-O4 are at ''L'' level in points B-D. Then, a current flows to resistors R1, R5, R9 and R13 from the point A at ''H'' level and it flows to GND entirely, then a signal from the output port O1 does not flow to input ports I1-I4 at all. When the sensor S1 is opened, the current flowing to the resistor R1 flows to a resistor RG1 via a diode D1 and the GND, a voltage drop VG[V] is generated by the current flowing to the resistor RG1 and a signal is inputted to the input port I1 of a CPU. |
