This post is all about how to build digital voltmeter. You may download code and Proteus Simulation from the download section at the bottom of this post. I am using MPLAB X IDE, C30 Compiler and Proteus Simulation on v8.0 This code will work on PIC24, DsPIC33 and DsPIC30 (16bit microcontroller) by slightly changing the code.
In this post I supposed that you know following things if not then please go through following posts before proceeding with this.
- How to Blink an LED. (Click here)
- How to get input at a certain pin. (Click here)
- How to interface an LCD. (Click here)
- How to configure ADC module. (Click here)
In the following figure 1. I used a variable resistor as a dummy voltage divider so simulate the difference in voltages from (0 to 50VDC). This digital voltmeter will only measure voltage from 0 to 5volts (Warning!!! Measuring greater than 50 volts may damage microcontroller permanently). I used potential divider with 90kOhm and 10kohm. Which ensures that at 50 volts there is 5 volts max at the PIN of microcontroller (AN0 or RA0). In real you may remove variable resistor and replace it with a probe. This will be your home made voltmeter for measuring voltage upto 50 volts max.
|Figure 1. Proteus Circuit|
In the following figure 2. When I change value of voltage at channel 0 of ADC with the help of variable resistor. The voltage measure by the probe named R3(1) as shown in figure 2 is same as shown on LCD. For instance by the help of animation I shown different voltage values at different voltage applied to R3 resistor.
|Figure 2. Proteus Simulation|
In the following figure 3. This is main function in which I first initialize LCD, then I configure ADC with Channel 0. And a loop which only calls a function named DisplayVoltage() which is responsible for displaying voltage value on LCD.
|Figure 3. Main function|
In the following figure 4. We have DisplayVoltage() which has a string that is printed directly and a variable named “PotentialDivider” whose value depends on what R3 and R2 for this particular example it is calculated by this “ voltageoutput = (R2/(R2 + R3))*Vcc”. Whereas I have max voltageoutput is 5volts. R2 = 10k, R3 = 90k, vcc = ? which we want to measure. So I get this vo * 10 = vcc which is shown in figure 4 line no. 24. In line no. 21 I simply convert that adc value into voltage by this formula voltage = (ADCvalue/ADC resolution) * Vref. And then multiply that with 1000 in order to get value in millivolts. So at last I got vcc value in variable named VoltageMeasured which is shown on LCD by passing it to a function named WriteIntegerAsFloatUptoFiveFigures() as parameter. Note that I type cast these variable from unsigned int to float and from float back to unsigned int to make calculations more accurate.
|Figure 4. Display voltage.|
- I2C PIC24, DsPIC33, DsPIC30code and Proteus Simulation.
- PWM generation using PIC24, DsPIC33, DsPIC30.
- PIC24, DsPIC33F and DsPIC30F UART implementation.
- Digital Clock using PIC and LCD 16x2 with time Set function.
- How to get interrupt on change of logic on Pins (Input Change Notification).
- Generating Perfect Delay without using timers.
You can download Code (MPLAB X IDE and C30 compiler) and Proteus (v8) Simulation Click here
For all topics Click here.
That’s all for this post hope you will learn please comment if you have any questions.
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