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Zero Crossing Detector

Zero crossing detector is a electronic circuits that has a function to detect the existence of the zero  crossing voltage, either positive or negative changes. This circuit serves to provide information to other systems that need it, for example, to detect the phase shift between current and voltage, or to switch thyristor circuit.

The circuit in Figure 1 is a circuit of zero crossing detector to detect a positive change (output 1) and to detect changes in negative (output 2). On the positive going zero crossing detector (op-amp output 1), input on pin 3 will be compared with the input on pin 2, when the voltage at pin 3 is greater than zero, then output 1 will be high, when the voltage at pin 3 is smaller than zero, the output 1 will be low. This occurred opposite the op-amp circuit output2. Output 1 and 2 can be seen in figure 2.

The circuit in Figure 1 can be connected to the system microcontroller to activate the system interruption, which can later be used as required.

Figure 1. Positive and Negative Going Zero Crossing Detector.

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