Raspberrypi Current and Temperature Sensor Adaptor

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RPICT Series

RPICT series are a set 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.


Raspberrypi Stackable Boards
V 2 & 3

V 4

V 5

Raspberrypi & 400A or more CT

Raspberrypi Zero

  • RPIZ_CT3V1 - 3 CT 1 AC Voltage. Raspberrypi Zero.
  • RPIZ_CT3T1 - 3 CT 1 Temperature. Raspberrypi Zero.
  • RPIZCT4V3T1 - Rpi Zero 4 CT 3 AC Voltage 1 Temperature
  • RPIZCT4V3T2 - Rpi Zero 4 CT 3 AC Voltage 2 Temperature (RTD & DS18B20)

Model #CT #Volt* #Temp Stackable
RPICT3T1 3 - 1 No
RPICT3V1 3 1 - No
RPICT4T4 4 - 4 No
RPICT4V3 v1 4 3 - 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

Insert on Raspberrypi

Insert board here.png

Power is provided from the Raspberrypi. There is no need for extra power supply.

First Time Use

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

Howto setup Raspbian for serial read

Also carefully read the Frequently Asked Questions

Current Sensor


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

Connector: 3.5mm Jack

Measured range

The range is determined by the burden resistor fitted on the RPICT unit.

The default range is 100A on all RPICT series which correspond to a burden resistor of 24 Ohm. The table below shows alternative ranges with their associated burden resistor values. The range is for rms value.

Sensor Range
(Rms Amps)
Burden Resistor
Calibration Coefficient
Input rating (mA)
SCT-013-000 100 24 83.33 50
60 39 51.28 30
50 47 42.55 25.0
40 56.2 35.59 20.0
30 75 26.67 15.0
25 91 21.98 12.5
20 120 16.67 10.0
SCT-006 20A/25mA 20 47 17.02 25.0
SCT-019 200A/33mA 200 33 181.82 33.0
SCT-024 400A/100mA 400 12 333.33 100.0
SCT-031 600A/100mA 600 12 500.0 100.0

This table above does not apply to RPICT7V1 RPICT4V3 and RPICT8 versions 4 and 5. Version 4 uses 10Ω burden resistor regardless of sensor. See this page for version 5.


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

We offer a set of AC/AC transformers to measure Voltage. These units can be easily plug in a main wall socket. No wiring is required.

The three different models we recommend are:


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.

This is only available for RPICT7V1 Version 4 & 5 and RPI_DCV8.


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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 -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
See also. Recording RPICT Serial stream on local file

Using InfluxDB and Grafana

GRAFANA 001.png

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.

See this guide proposing a solution to send data to an Influxdb database.
Example Using InfluxDB.

Also see
Install an InfluxDB Grafana stack on a Raspberrypi

For a readily hosted solution with Influxdb/Grafana see Corlysis.

Using Home Assistant - home-assistant.io


If Home Assistant is run on the Raspberrypi you can configure it to read on the serial port directly.

The link for serial configuration on home assistant website is here.

A basic yaml config for a RPICT3T1 is shown below:

# Example configuration.yaml entry
 - platform: serial
   serial_port: /dev/ttyAMA0
   baudrate: 38400

 - platform: template
       friendly_name: CT1
       unit_of_measurement: "W"
       value_template: "{{ states('sensor.serial_sensor').split(' ')[1] | float }}"
       friendly_name: CT2
       unit_of_measurement: "W"
       value_template: "{{ states('sensor.serial_sensor').split(' ')[2] | float }}"
       friendly_name: CT3
       unit_of_measurement: "W"
       value_template: "{{ states('sensor.serial_sensor').split(' ')[3] | float }}"
       friendly_name: Temperature
       unit_of_measurement: "°C"
       value_template: "{{ states('sensor.serial_sensor').split(' ')[4] | float }}"

See Also

Credit to ned-kelly on Github for making an interface between RPICT series unit and Home-assistant. This is easily installed with Docker. Follow the link below to find out more.


Using OpenHAB Domoticz HomeGenie mycontroller.org

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

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 lechacal.com/repo/emonwrt3/lighttpd.conf -O /etc/lighttpd/lighttpd.conf
sudo /etc/init.d/lighttpd restart
wget lechacal.com/repo/emonwrt3/emonwrt3_rpi_armhf_v1.0.1.deb
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 req emonwrt3 01.png

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.

Using Emonhub format - Emonpi image [Recommended]

If you are using this option then you should download the emonpi image from this link below.


Flash this image onto a SD card. Once the Raspberrypi powered up point your web browser to http://emonpi. Then modify the emonhub configuration as shown below.

Delete or backup the entire content of Emonhub configuration and replace with this one below.

### loglevel must be one of DEBUG, INFO, WARNING, ERROR, and CRITICAL
### see here : http://docs.python.org/2/library/logging.html
loglevel = DEBUG #(default:WARNING)


  Type = EmonHubSerialInterfacer
      com_port = /dev/ttyAMA0
      com_baud = 38400
     pubchannels = ToEmonCMS,

   Type = EmonHubEmoncmsHTTPInterfacer
       subchannels = ToEmonCMS,
       #url = http://localhost/emoncms #uncomment to save on local pi
       apikey = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
       senddata = 1                    # Enable sending data to Emoncms.org
       sendstatus = 1                  # Enable sending WAN IP to Emoncms.org MyIP > https://emoncms.org/myip/list
       sendinterval= 30                # Bulk send interval to Emoncms.org in seconds


  nodename = my_RPICT7V1
     names = RP1, RP2, RP3, RP4, RP5, RP6, RP7, Irms1, Irms2, Irms3, Irms4,Irms5,Irms6,Irms7,Vrms
     scales = 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
     units =W,W,W,W,W,W,W,mA,mA,mA,mA,mA,mA,mA,V
     datacode = 0

Replace the apikey with the one given by your Emoncms account. Use the Read and Write key.
Modify the [[11]] entry as needed. Refer to the board specific page to modify the last part of the config where it starts with node ID.

Using Emonhub format - Raspbian image [Alternative Option]

It is possible to use a native Rapbian image and install only emonhub to forward the data. In this case you will miss the web interface to the raspberrypi. For this follow the guide below.

Use Emonhub with RPICT

Using the gateway tool to forward the data [Alternative Option]

We are proposing a basic script template which can be installed as below.

wget lechacal.com/RPICT/tools/lcl-gateway.py.zip
unzip lcl-gateway.py.zip
wget lechacal.com/RPICT/tools/gateway.conf
sudo apt-get install python-requests
sudo mv lcl-gateway.py /usr/local/bin/
sudo mv gateway.conf /etc/

Edit the gateway.conf file to reflect your own setting. Content will be self explanatory.

sudo nano /etc/gateway.conf

Insert the RPICT and run

lcl-gateway.py -d

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 python-serial package installed

$ sudo apt-get install python-serial

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

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

       while 1:
               response = ser.readline()
               z = response.split(" ")
               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][:-2]
except KeyboardInterrupt:

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


Spiotrealtime 001.png

Download and install SPIOT on a given server. This could be the raspberrypi itself.

From the downloaded archive there is a directory called rpi containing python scripts and configuration file. Copy all these files on the raspberrypi (if not already there).

Make sure all .py files are executable:

$ chmod 755 *.py

Open the spiot.config file and modify the csv_forward section. port and hostname variable will be the most important ones for a first test. Keep apikey and node as they are to follow this example.

port = /dev/ttyAMA0
hostname = myserver/spiot
apikey = qbG31dQxFlG55mNM8G5ZTFkF0mrUbWg5
node = 20
baud = 38400

Then run the spiot_csv.py utility.


Then point your webbrowser to the link below:


The last 5 minutes of the first channel will be shown on a graph.

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.




Some RPICT have enclosures available as 3D printed product.

See the shop item for
RPICT3T1 Enclosure
RPICT3V1 Enclosure
RPICT8 Enclosure
RPICT7V1 Enclosure
RPICT4V3 Enclosure

Related Howto

Frequently Asked

Howto setup Raspbian for serial read

First time troubleshoot for RPICT

Example Using InfluxDB


Use Emonhub with RPICT

Burden Resistor calculation

How to program an Attiny85 or Attiny84

RPICT Online Config Generator


Transform a RPICT into a web scope

Noise level test RPICT V2&3

RPICT and Node-Red hosted on Raspberrypi


Compute Energy used using a RPICT

External Resources

An enclosure alternative for RPICT7V1