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"Raspberrypi Smart Meter"

RPICT Series

RPICT series are a range of Raspberrypi hat for AC current sensor (CT) and temperature sensor. This page introduces generalities concerning the RPICT series. Information for each individual board can be found below.

All RPICT board connect to the GPIO connector and provide data via the serial port. An Arduino programmable microcontroller (ATtiny84 or Atmega328) operates the board. Source code for the microcontroller is freely available.

There are various options for logging and viewing the data. Most commonly used are Emoncms and Influxdb with Grafana. Using your own Python script is also possible.


  • Raspberrypi Smart Meter.
  • Internet of Things.
  • Data Logging.
  • Real Time Monitoring.
  • Home Automation.

"AC monitoring"


Raspberrypi Stackable Boards V 2 & 3

V 4

V 5

V 6

Temperature Only

Raspberrypi for 5A output CT

Raspberrypi Zero

  • RPIZ_CT3V1 - 3 CT 1 AC Voltage. Raspberrypi Zero.
  • RPIZ_CT3T1 - 3 CT 1 Temperature. Raspberrypi Zero.
  • RPIZCT4V3T2 - Rpi Zero 4 CT 3 AC Voltage 2 Temperature (RTD & DS18B20)

with relays

Model #CT #Volt* #Temp Stackable
RPICT3T1 3 - 1 No
RPICT3V1 3 1 - No
RPICT4T4 4 - 4 No
RPICT4V3_v2.0 4 3 - Yes
RPICT7V1_v2.0 7 1 - Yes
RPICT8 8 - - Yes
RPIZCT4V3T1 4 3 1 n/a
RPI_T8 - - 8 Slave 1 only
RPI_LCT4V3 4 3 - One board stack only
RPI_LCT8 8 - - One board stack only

\* AC Voltage

First time use

Insert on Raspberrypi

Insert Hat on Raspberrypi

Insert the RPICT board on the Raspberrypi GPIO as shown above. The picture is a RPI3B but all other Raspberrypi are also compatible.

The RPICT boards gets power from the Raspberrypi. Just connect the USB power adaptor to the Raspberrypi as normal.

Raspberrypi Configuration

If using Raspberry Pi OS follow the guide below to get the Raspberrypi ready for use with the RPICT.

Howto setup Raspbian for serial read

Next steps

  • The board is sold ready to go with firmware and configuration already loaded.
  • Make sure to test all sensors with the cat or lcl-run command before changing the configuration.
  • Carefully read the FAQ below

FAQ - Frequently Asked Questions

First configuration

First Configuration RPICT

Current Sensor

right | 240px

Any current sensor with current output is compatible. Note there are considerations for the burden resistor which scales the range of measured current. We recommend the sensor below to start with.

Recommended sensor:

  • SCT-013-000 100A/50mA
  • SCT-019 200A/33mA
  • SCT-006 20A/25mA
  • SCT-024 400A/100mA
  • SCT-031 600A/100mA

Connector: 3.5mm Jack

Measured range

The range is determined by the burden resistor fitted on the RPICT unit. At purchase time this is selected using the parameter rating in the shop.

The default range is 100A on all RPICT series which correspond to a burden resistor of 24 or 27 Ohm. Other ratings (or ranges) can be selected at purchase time.

More details about the input range and the burden resistor is given in the links below.

For RPICT3T1 RPICT3V1 RPICT4T4v2.5 and also RPICT8/RPICT7V1/RPICT4V3 in version 3:

Gen3 Passive Component Setup

For RPICT7V1 RPICT8 and RPICT4V3 in version 4:

Gen4 Passive Component Setup

For RPICT7V1 RPICT8 RPICT4V3 in version 5:

Gen5 Passive Component Setup

For RPICT3V1T1 in version 6:

Gen6 Passive Component Setup


CT sensors only measures Alternating Currents (AC). Refer to sensor ACS715 for DC current.

Only RPICT7V1 Version 4 and RPI_DCV8 can support voltage output CT. SCT-013-xxx other than SCT-013-000 and any voltage output CT are not supported for all other boards.

Voltage Sensor

To evaluate the power of an installation a voltage sensor is not strictly necessary. Power can be estimated using an estimated fixed voltage (usually 240 or 110V). Voltage sensor becomes necessary if you wish to measure more accurately Real Power, Apparent Power and Power Factor. The combination of a voltage sensor with a CT sensor will also provide the direction of power (import/export).

In any case power readings with voltage sensor are more precise and consistent. They also have much lower noise and are better for low power readings.

The RPICT series are shipped using a basic calibration for the voltage port. A calibration would be needed if you feel the measured voltage is not accurate enough against another well trusted measuring device (scope, multimeter). Use this page to calibrate the voltage port.

AC/AC Voltage Sensor

Low Voltage < 250V

The three models available depending on mains power type:

ac/ac transformer

These units can be easily plug in a main wall socket. No wiring is required.

Three units are needed to monitor 3 phase.

High Voltage up to 1500V


The TV30GB can read Voltages up to 1500V. Wiring required.

Three units are needed to monitor 3 phase.

ZMPT101B Module

The ZMPT101B module is a voltage module to be wired. It measures voltages up to 250V and can be mounted on DIN rails.

For single phase: ZMPT101B_Module_1x_v2

ZMPT single Phase

For three phase: ZMPT101B_Module_3x_v4

ZMPT Three phase

No ZMPT Do not use these ZMPT module sold on the market. They do not scale against the RPICT units and the presence of a potentiometer make them unreliable.

Temperature Sensor


The temperature sensor is the DS18B20.

Temperature sensors come with various connectors.

3 pin Molex

This applies for board RPIZCT4V3T1 and RPIZCT4V3T2.

Bare wires

This applies for boards RPICT3T1 RPICT4T4 and RPIZ_CT3T1. Connectors are screw terminals. Temperature probe should present bare wires for connecting.

Our DS18B20 Junction board requires bare wires for connection.

Power Supply

The raspberrypi should use the usual micro-usb PSU.

The RPICT series do not need any extra PSU. Power for the RPICT is taken from the Raspberrypi GPIO.

View/Record data

In the most basic use the RPICT series only output a serial string. It is down to the user to collect this data string and record/view as needed. We offer below various way to achieve this.

  • Using cat command.
  • Using Influxdb and Grafana.
  • Using a Json request.
  • Using Emonhub tool from Emoncms.
  • Using a Python script.

Using plain Linux terminal - CAT command

This option reads data output from a linux terminal using the cat command. Direct reading of the serial port.

Note: This is the most basic usage. We highly recommend to make use of this first before anything else.

Before hand make sure you have followed this guide if you are using the Rasbian image. Let's use the RPICT3T1 as an example. The format of the output is as shown below. Powers in W. Temperature in deg Celsius. For any other RPICT unit refer to its specific page to know the default output format.

nodeid power1 power2 power3 temperature

Log in the Raspberrypi using ssh and issue the commands

stty -echo -F /dev/ttyAMA0 raw speed 38400
cat /dev/ttyAMA0

The terminal should then show something like this below

pi@raspberrypi ~ $ cat /dev/ttyAMA0
11 46.23 52.25 126.56 19.46
11 47.43 52.28 129.60 19.54
11 48.90 53.88 131.22 19.89

To figure out which channel correspond to which measured value refer to the specific board dedicated page.

Note. If using the emonpi image run the command below before the stty command.

sudo /etc/init.d/emonhub stop

See another alternative here. Using plink To record the data in a text file see Recording RPICT Serial stream on local file

Using InfluxDB and Grafana

Grafana Dashboard InfluxDB is an open source project backed by Influxdata. It is all free if you install on your own server. Only a hosted solution is payable.

InfluxDB on its own is just a database ready to store the data. Data can be viewed with Grafana or directly inside Influxdb.

See this guide proposing a solution to send data to an Influxdb database. Forward to Influxdb from RPICT

See also Install an InfluxDB Grafana stack on a Raspberrypi

Using Home Assistant -

Follow this guide below for Homeassistant.


Using OpenHAB Domoticz HomeGenie Jeedom

We have not yet documented any of these platform yet. Please contact us to notify your interest in using them with RPICT series board.

Jeedom. Credit to tlierdotfr on Github for making a plugin for Jeedom.

Using Node-Red

See the link below for an example using Node-Red.


Using JSON request

The Raspberrypi can be setup to serve Json requests on http.

Preliminaries. This is for a Raspbian default image. This guide should be completed first.

Issue the commands below. This installs a http server. Configure it and setup the binary of emonwrt3. Emonwrt3 aims to save the data into a rolling database.

sudo apt-get install lighttpd
sudo wget -O /etc/lighttpd/lighttpd.conf
sudo /etc/init.d/lighttpd restart
sudo dpkg -i emonwrt3_rpi_armhf_v1.0.1.deb

Once complete you should be able to request the json data using the address below.


Modify last=1 to the number of records you need to acquire. Remove the variable altogether to obtain all data (default limit is 128 records).

The web browser will show the data as below. Number of channels will depend on the unit used. Our example here as 4 channels CH_00 to CH_03. Json Output Energy Monitoring

Using Emoncms

Emoncms is a very complete and user friendly interface. Emonhub is used to forward the data from the RPICT to the Emoncms service. We also show some alternatives below.

Emoncms and RPICT on the same Raspberry

Emoncms and RPICT on the same Raspberry

Forward to a remote Emoncms server

There are 2 ways to do this. The first one is using our gateway tool called lcl-gateway. The second one involves installing Emonhub alone.


Get the lcl-gateway tool and install it this way.

sudo dpkg -i lcl-gateway_2.1.0_armhf.deb

Edit the lcl-gateway.conf file to reflect your own setting. Content is self explanatory.

sudo nano /etc/lcl-gateway.conf

Insert the RPICT and run

/usr/local/bin/ -d


An alternative way is to install Emonhub on the raspberry. See this guide.

Use Emonhub with RPICT

Using Python basic script

Using the same sketch as mentioned above a python script can be used to work with the data. The example script below will be a good starting point.

First of all make sure you have python3-serial package installed

sudo apt-get install python3-serial

Then copy the following into an executable file and run it.

import serial
ser = serial.Serial('/dev/ttyAMA0', 38400)

       while 1:
               # Read one line from the serial buffer
               line = ser.readline().decode().strip()
               # Create an array of the data
               z = line.split(" ")

               # Print it nicely
               if len(z)>=3:
                       print("Power 1: %s Watts" % z[1])
                       print("Power 2: %s Watts" % z[2])
                       print("Power 3: %s Watts" % z[3])
                       print("Temperature: %s Degrees" % z[4])
except KeyboardInterrupt:

The above example is for the RPICT3T1 board. If using a different RPICT refer to the page of that particular board.

Full Output Firmware

For the most advanced user who code things themselves and do not use any readily made platforms like emoncms or influxdb we have a special firmware that produces an output with the most complete information.

RPICT Full Output Firmware

This firmware brings in the additional features

  • Relative timestamping to MCU boot time.
  • One line per computation result. This means that data computed together are packed together and not mixed with other computation results.
  • Data are sent along with the ports and level information that was used to compute them. This alleviate the need to know a user defined data field format.

Flashing the firmware / Upload Sketch

There is no need to flash the firmware (sketch) if you have just purchased the unit. They are sold ready to run. There is no need to reflash the microcontroller if you wish to change parameters. The board can be configured using the Raspberrypi. See relevant configuration documentation for this.

The reasons one would flash a new firmware are:

  • Update to a new version.
  • Flash your own sketch.

The onboard microcontroller can be re-programmed using the Arduino IDE software and an AVR programmer. We recommend our NanoProg programmer for this.

RPICT series come with 2 type of microcontrollers. Attiny84 and Atmega328p. See below.


These boards use attiny84 mcu.

This link is a tutorial to upload Arduino sketches to the Attiny84. .


These boards use atmega328p mcu.

Upload Arduino sketch to Atmega328.

Developing Arduino Sketch

There is no need to know how to program or even flash any firmware to use any of the RPICT series. They all come with a ready to use firmware (or Arduino sketch). Nevertheless it is possible to modify or edit your own arduino sketch. RPICT series are well inclined for this purpose.

To make things easier we have developed the RPICTlib. It contain functions to easily compute all aspect of AC signal such as RMS value or Active Power and more.

The link below is an introduction to this library with plain simple examples.



Enclosure for RPICT Series

Some RPICT have enclosures available as 3D printed product.

See the shop item for RPICT3T1 Enclosure

RPICT3V1 Enclosure (uses the same as RPICT7V1)

RPICT8 Enclosure

RPICT7V1 Enclosure

RPICT4V3 Enclosure

Frequently Asked

Howto setup Raspbian for serial read

First time troubleshoot for RPICT

Upload Arduino sketch from Raspberrypi to RPICT

Example Using InfluxDB


Use Emonhub with RPICT

Burden Resistor calculation

How to program an Attiny85 or Attiny84

RPICT Online Config Generator (old)

RPICT Configuration Web Tool (new)

RPICT Fundamentals

Remote terminal access with tmate

Upgrading to sketch version 4

Burn bootloader on RPICT Atmega with Arduino UNO


Transform a RPICT into a web scope

RPICT and Node-Red hosted on Raspberrypi


Compute Energy used using a RPICT

Timestamping with RPICT

Add a relay board to RPICT

Third Party Developments

All of the links below are not managed by LeChacal. We think they might be of interest if you need inspiration. Contact us if you want your project to be added to the list below.

An enclosure alternative for RPICT7V1

'myPower' Power monitoring and logging developed by KM6WYE

Homeassistant module

An exporter for Prometheus on Github

for RPICT3T1 to MQTT

rpict-mqtt / A package delivering MQTT support for RPICT

A Low-Cost and Do-It-Yourself Device for Pumping Monitoring in Deep Aquifers