Logic Probe Based on PIC12F683 Microcontroller

A simple PIC12F683 microcontroller was used to create a logic level tester which has the capability of measuring 5V TTL up to 24V PLC logic levels.

An input stage supplements the circuit which will adapt the signal to the levels between the microprocessor while the state in which the point is measured will be visually shown in another output stage. The probe can indicate if the test point has high impedance via yellow LED, a logic 0 via red LED, and a logic 1 via green LED. The probe goes to sleep mode after 3 minutes until the button is pressed again and new measurement is made, since the device is battery operated. The internal timer of the program saves the battery life and reduces the consumption during sleep mode.

In addition to having analog inputs and internal oscillator, being able to operate at low voltages as its nature is one feature of the PIC12F683. A fixed value for the input of the microcontroller can be established to signify a state of high impedance by including a voltage divider in the input stage. The voltage drop will vary on the input signal.

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