Simplified Bi-polar Volt Amp Meter
This project is for displaying positive and negative voltage and current consumption for an existing Bi-polar ( +ve and -ve ) DC power supply, which is made as a module for easy addition to the front panel.
Most of the modules available, either can't read negative voltages and currents or costly for a hobbyist. The circuit is simple and requires single positive power supply (from 8VDC to 12VDC).
Refer full circuit diagram:
Here, ATMEGA8 micro-controller is the heart of the project. The ADC channels of the MCU continuously reads the voltages available at the 4 pins (23,24,25 & 26), then process and display on 2 row 16 column LCD display.
Positive voltage is divided using resistance dividers and negative voltage is converted to positive voltage using LM358 ( One OP-AMP is used out of Dual OP-AMP IC ) and powered by separate 6V supply through fixed voltage regulator IC 7806. The remaining circuit is powered through another fixed voltage regulator IC 7805.
The current is measured using ACS712-5A modules, which can measure current from -5A to +5A. Two similar ACS712-5A modules are used for positive and negative current measurement and the circuit and application for connecting the modules are shown below.
Initial Setup / Calibration :
Once the components are soldered on the PCB ( a general purpose PCB is used here ) as per the circuit, the BipolarVAmeter.HEX file is to be uploaded to ATMEGA8 using any suitable programmer using its ISP port.
After connecting power supply to the circuit ( 9V battery is preferred ), power ON the circuit. Now, connect positive and negative power supply connections to input for positive voltage and input for negative voltage for voltage measurement. Read the input voltages on multi-meter (voltage mode) and adjust the 200K trimpots to display the same voltage on LCD.
For current reading calibration, connect the two numbers of ACS712-5A modules as shown in the figure in series with a multi-meter in 10A mode. A small PCB has to be made with the two buttons connecting to pins 4 & 5 of ATMEGA8. Now, restart the circuit with power off and on (or press reset button).
Read the current flow in amperes on multi-meter, LCD for positive and negative values. if the LCD is displaying null value (0.0A) then reverse the power input connections for the particular ACS712-5A module after switching off power supply to the circuit.
If, the displayed value (amperes) are not matching with the multi-meter value, then note down the error percentage for positive and negative amperes on LCD, w.r.t. to multi-meter value.
Now, reset the circuit and just press any button, while Title of the project (Simplified Bipolar Volt Amp Meter) is displaying on the LCD.
Some Multiplication Factors for negative and positive ampere values are displayed successively. Press BUTTON_UP or BUTTON_DN buttons to increase or decrease the values as per the percentage error is observed. Now, the meter displays the current in amperes with the corrected values.
The above process has to be repeated until the ampere values displayed on the LCD should be matched with value on multi-meter.
Once, the Initial Setup is completed and calibrated, then the circuit is ready to use. The circuit to connect the Volt Amp module to existing power supply and final assembly on the front panel is shown here.
ENJOY. ALL THE BEST.
click the link / attachment to download the file and rename as BipolarVAmeter.HEX , then upload to ATMEGA8 using any suitable AVR programmer.
For source code (in C-language), (BipolarVAmeter.C) please send message through contact form. The code will be sent to your e-mail.
Simplified Bi-polar Volt Amp Watt Meter
This project is EXTENSION for Simplified Volt Amp Meter project, which displays Watts and Summary in addition to Volts and Ampleres for both positive and negative DC voltage and current consumption.
The main difference is, LCD is to be changed to 4 rows x 16 columns instead of 2 rows x 16 columns. There is no change in circuit. Write the new HEX code available below (download by clicking the link) to ATMEGA8. The value of WATTS is obtained by multiplying voltage and current consumption. The summary contains total current and total wattage (both positive and negative power consumption).
Make suitable panel to accomodate 16x4 LCD. Rest of the things are same as explained above.
ENJOY. GOOD LUCK
click the link / attachment to download the file and rename as BipolarVAWmeter.HEX , then upload to ATMEGA8 using any suitable AVR programmer.