Fundamental Source and sink for PLC
Source and sink
The terms “good” and “well” at the bottom of which flows in the direction of the flow as a signal “runs” or activation of a signal. a simplified representation of the output circuits of a logic gate. The circuit uses two transistors, but one lit at all times.
* When the transistor is switched “On” is the question of a “source of power supply voltage of the logic gate, and is a strong” logic “level.
* When the transistor is switched “B”, the output of a current sink to the ground following the logic gate, and represents a low “logical level.
It is important that most logic gates can remember, “the source” and “good” a very small amount of current, typically of the order of several milliamps, sufficient to relays, LEDs and other devices operate directly.
Pullup Resistors
Resistors are often used for “source” current to supply logic “go” signal to a logic “high” level. In this way, switches, relays, switches and other devices draw current through the resistance offered to the earth, so the signal to a logical “Go Low” level. The resistance values are generally the highest place in the voltage that the device must reduce border. Some of the following figures show a resistance to draw, in conjunction with switches and relays used contacts.
