Elektor_Mag_-_January-February_2021

84 January & February 2021 http://www.elektormagazine.com

The intent is that the module is fitted into a circuit or device where

voltage and current is to be measured. The measurement module

requires an external 12 V supply voltage. The temperature sensor,

if needed, can be connected to a small connector on the PCB.

Display

There are two options for linking the display module to the

measurement module. You can use the included USB cable to

connect it directly to the measurement module or you can use the

built-in wireless connection. A wireless connection is established

automatically if the USB connection is not available. According

to the manufacturer, several modules can be used at the same

time with up to 26 channels possible simultaneously. Obviously,

when using the wireless connection, the display module must be

provided with its own supply voltage. This can be achieved using

the micro USB port (5 V) or via a two-way JST connector (8–16 V)

for which a matching cable is included.

The display measures approximately 3 × 2.5 cm and is very bright, so

it is easy to read even under high ambient light conditions. There are

three touch-sensitive buttons next to the display. By default the display

shows the measured voltage and current together with the time at

the start of the measurement cycle. A battery icon can be displayed

on the left to indicate the remaining battery capacity after a nominal

battery capacity has been entered. The connection mode, relay state

and measured temperature are shown at the top of the screen.

Even more information appears when you touch one of the buttons.

This adds the display of the supplied or consumed power beneath

the voltage and current. In a further, smaller area you can see how

many ampere-hours the power source or battery has supplied, the

number of watt-hours, and the elapsed usage time. On the right there

is a list with a number of menu items that you can scroll through

with the up and down keys. We cover these in more detail shortly.

Potential applications

This set of display and measurement modules can be used for

various purposes. For example, you can measure the current

suppled to a load by a power source. If the power source is a battery

A lot of current
The version described here is suitable for DC voltages of up to 100 V
and currents of up to 30 A. There is also a version that can handle
up to 100 A but, unless you want to make measurements on car
batteries or the like, 30 A should be enough in most cases. The
measurement module consists of a small plastic box with several
openings in the cover. These allow you to connect the cables and
the power supply to the screw terminals inside the box.

The internals of the box consist of a sandwich of two PCBs
(Figure 2). The top PCB holds all the screw terminals and a large
relay while the bottom PCB contains the control circuitry and a
2.4 GHz transceiver module for wireless communication with the
display module. It looks a lot like an ESP8266 WiFi module but,
as the chip is hidden beneath a drop of glue, we can’t be sure. The
top part of the enclosure can be easily unclipped to provide good
access to the screw terminals.

+ – + –

DC 12V

+ – + –

Power

Source Load Battery Charger

DC 12V

Figure 2: The measurement module with the top cover unclipped.

Figure 3: The load on the output can be replaced by a battery charger. Measurements can be made in both directions.