HUM: BUILT-IN VOLTMETER + AMMETER, 100V 10A

You are a beginner with Dasduino. Or electronics? A specific module caught your eye, but you do not know how to use it? Do not worry, HUM is here for you! How to Use Module (HUM) is a blog tutorials series by soldered where you will find all you need in order to begin working with your favorite module. Tutorials include technical characteristics, work principles, instructions on how to connect the module with Dasduino and the basic code. Everything else is left to your imagination.

INTRODUCTION

When we need to measure voltage or current while working on a project, we can use a multimeter, but what if we had to constantly measure current and voltage? If you need to measure the voltage and current of the source or the load, a built-in voltmeter + ammeter DSN-VC288 is the right module for you. This module is designed for easy installation in the housing and shows us the value of voltage and current on a seven-segment display. What can be measured with this module and how to connect it is described below.

Module characteristics:
• Voltage measuring range: 0 V – 100 V
• Current measuring range: 0 A – 10 A
• Error: 1%
• Power supply of the device: 4,5 V – 30 V
• Voltage step: 1 V
• Current step: 0.01 A
• Dimensions: 48 mm x 29 mm x 26 mm

HOW DOES IT WORK?

The module measures voltage directly while measuring current indirectly using a shunt resistor. The shunt resistor is a lower value (less than 1 ohm) resistor on which we measure the voltage drop and then calculate the current according to Ohm’s law. The board has a built-in resistor using which we can measure currents of up to 10A, and if we want to measure higher currents we need to use the external shunt resistor shown in the image. On the board, we also have an n76e003at20 microcontroller, which is used for measuring and displaying measured values.

On the board, we also have two potentiometers using which we can calibrate the voltmeter and the ammeter to measure the exact values. If the ammeter or voltmeter show certain values when nothing is connected or we cannot adjust the correct value with the potentiometers, we can reset the module by short-circuiting the 2 pins marked in the image. After turning the module on, we should short-circuit the pins and remove the jumper after 3-4 seconds. When resetting the module, nothing has to be connected for measurement as the module is set to zero.

HOW TO CONNECT IT?

There are several ways to connect, depending on the amount of current we are measuring and whether the module has its own power supply or the load and the module are power supplied together using the same source. We use the yellow wire to measure the voltage, and red and black wires are used to power supply the module. Thicker black and red wires are for measuring current, and we must be careful not to connect the black wire (we must connect it to the GND) when connecting the module and the load to the same power supply.
When measuring less than 10A, we use a built-in shunt resistor, and if we have a common supply for the load and our module, we connect it according to Scheme 1.

When we need to measure a voltage greater than 30 V, we connect the module as shown in Scheme 2, so that we have one power supply for the module (0-30 V) and another for the load. According to this scheme we also measure current of up to 10A.

When we need to measure currents greater than 10 A, we must use an external shunt resistor of a certain value depending on the current we need to measure. Measuring current with an external shunt resistor is shown in Scheme 3, and the power supply is common to the module and the load. Scheme 4 shows the connection to an external shunt resistor but for the separate power supply of the module and the load.