11.6 PROJECT 11.6 – Digital Voltmeter

This project is about the design of a digital voltmeter device with LCD output. The device can be used to measure voltages from 0 V to +5000 mV.

The voltage is measured and displayed every second. The measured voltage will be displayed in millivolts and in floating point format as follows:

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11.6.1 Block Diagram

The block diagram of the project is shown in Figure 11.21.

Figure 11.21 Block diagram of the project

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11.6.2 Circuit Diagram

The circuit diagram of the project is shown in Figure 11.22. The LCD is connected to PORT B as before. The analogue voltage to be measured is applied to port pin RA0 of the microcontroller, and this pin is configured as an analogue input pin. The project is based on a PIC18F45K22 type microcontroller with an 8 MHz crystal clock, although most other PIC microcontrollers supporting A/D converters can also be used.

Figure 11.22 Circuit diagram of the project

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The connections between the microcontroller and the LCD are as follows:

LCD Pin Microcontroller Pin
D4 RB0
D5 RB1
D6 RB2
D7 RB3
R/S RB4
E RB5

The contrast of the LCD is controlled by connecting a 10 KB potentiometer to pin 3 of the LCD. The microcontroller ...

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