πŸ’‘ Details

Power

The Smart Powermeter can be powered in two ways: through the USB-C (only for programming and testing purposes) or through the AC Input, but not simultaneously.

AC Power

The HLK-2M05 module is a 2W AC-DC step-down switching power supply module, ready to receive 100-220V AC and deliver 5V DC that later on is reduced to 3.3V through an LDO (for the ESP32 module).

The board is designed to be powered directly through the screw terminal block. Before plugging the wires in, make sure they have no power.

Input

The Smart Powermeter supports up to 6 independent analog inputs ready to read CT clamps (or probes):

Pinout table

GPIO

Name

01

Probe 0

02

Probe 1

03

Probe 2

04

Probe 3

05

Probe 4

06

Probe 5

Regarding the kind of CT-clamps, I recommend the SCT-013 series, comming in a wide number of ranges and with a 3.5 jack connector:

_images/CT.png
_images/amps_to_amps.png

Model

Ratio

SCT-013-000

100A:50mA

SCT-013-005

5A:1V

SCT-013-010

10A:1V

SCT-013-015

15A:1V

SCT-013-020

20A:1V

SCT-013-025

25A:1V

SCT-013-030

30A:1V

SCT-013-050

50A:1V

SCT-013-060

6A:1V

SCT-013-000V

100A:1V

When selecting a CT clamp, it is crucial to consider the anticipated measurement range. This ensures accurate measurements and prevents exceeding the ESP32’s maximum reading range.

Note

The default CT clamp in the set is the SCT-013-000, which has the highest range in the series. However, for measurements at low power <10W, it may not provide the desired level of quality.

Each channel incorporates a simple internal circuit that adjusts the induced voltage from the CT clamp (proportional to the measured current) to prepare the signal for reading by the ADC of the microcontroller. For more details on the circuit, refer to this guide.

_images/Figure_1.png

In general, except for the SCT-013-000, the induced voltage can be read by the conditioning circuit mentioned earlier. However, if the CT clamp output is also a current, a burden resistor is necessary, for which a 22 Ohm is integrated. In case the burden resistor isn’t needed, a trace-cuttable jumper placed on the bottom layer can be carefully cut, as explained in the Jumpers section.

LED indicators

The Smart Powermeter offers a visual help to assist debuging the board through two LED indicators: Power and GPIO.

The Power LED indicator is disconnected by default, under normal working circumstances this would be an unnecesary energy waste. For enabling it you just need to solder the jumper placed side the silkscreen bulb, located on the bottom layer. For more info, visit the Jumpers section.

The GPIO indicator is directly attached to GPIO 08, and can be turned on/off directly on the firmware uploaded, without any need of intermediate jumpers.

E-paper

The Smart Powermeter offers support for a 2.9” black and white e-ink display, through a clamp connector. The pinout with respect to the ESP32 GPIOs goes as follows:

_images/epaper.png
Pinout table

ESP32

E-paper

14

BUSY

15

RST

13

DC/MISO

12

CLK

11

MOSI

10

CS

Communications

In addition to the analog input mentioned before, there is also a direct connection to:

IIC (\(I^2C\)) bus:

This port is not accessible from external pins, but internally connected to a BMP280 sensor that can offer info about environmental temperature & pressure:

SDA

GPIO33

SCL

GPIO34

Serial bus:

Tx

TXD0

Rx

RXD0

Enclosure

The Smart Powermeter has been designed to fit in the electronics enclosure LK-PLC01, compatible with DIN rails and screws, and it is recommended for indoors only.

_images/enclosure.png
External size

115x90x40mm

Material

ABS Plastic

Color

Transparent cover, black or beige base