Raspberrypi Current and Temperature Sensor Adaptor
- 1 RPICT Series
- 2 Insert on Raspberrypi
- 3 Current Sensor
- 4 Temperature Sensor
- 5 Voltage Sensor
- 6 Power Supply
- 7 View/Record data
- 8 Flashing the firmware / Upload Sketch
- 9 Related Howto
RPICT series are a set of Raspberrypi adaptor for current sensor (SCT) and temperature sensor. This page will introduce generalities concerning the RPICT series. Information for each individual board can be found below.
- RPICT3T1 - 3 CT 1 Temperature.
- RPICT3V1 - 3 CT 1 AC Voltage.
- RPICT4V3 - 4 CT 3 AC Voltage.
- RPICT4V3_v2.0 - 4 CT 3 AC Voltage.
- RPICT4T4 - 4 CT 4 Temperature.
- RPICT7V1_v2.0 - 7 CT 1 AC Voltage.
- RPICT8 - 8 CT.
- RPIZCT4V3T1 - Rpi Zero 4 CT 3 AC Voltage 1 Temperature
- RPI LCT3V1 - 3CT 1 Voltage for large CT.
|Model||#CT||#Volt*||#Temp||Stackable||Config over serial**|
\* AC Voltage
\** Configuration over serial - The board can be configured from the serial port of the Raspberrypi (no need for an avr programmer).
All RPICT board connect to the GPIO connector and provide data via serial interface. An Arduino programmable microcontroller (ATtiny84 or Atmega328) operates the board. Source code for the microcontroller is freely available and can be modified for adaptation.
There are several options for logging and viewing the data. Python or Emoncms or anything able to read a serial port.
Insert on Raspberrypi
Note all RPICT series boards are compatible with all Raspberrypis.
Power is provided from the Raspberrypi. There is no need for extra power supply.
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.
- SCT-013-000 50mA/100A
- SCT-019-000 33mA/200A
Connector: 3.5mm Jack
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.
SCT-013-xxx other than SCT-013-000 are not supported. Likewise for any voltage output CT. Use the current output SCT with adequate burden resistor instead.
CT sensors only measures Alternative Currents (AC). Refer to sensor ACS715 for DC current.
Do not be tempted to use voltage output SCT sensor like SCT-013-030 or similar. All these SCT are SCT-013-000 with a burden resistor fitted inside them. However this is clearly not the best option as they are scaled for 1V output. Arduino microcontroller use 3.3V or 5V. We fit the burden resistor on the RPICT series for optimum scaling.
Connector: 3.5mm Jack
The intended temperature sensor is the DS18B20 which can be configured in either parasite or normal mode.
Temperature sensors come with various connectors.
3 pin Molex
This applies for board RPIZCT4V3T1.
This applies for board RPICT3T1.
An AC/AC adaptor is used to measure Voltage. We have a set of recommended adaptors:
- UK: 77DB-06-09
- EU: 77DE-06-09
- US: 77DA-10-09 or STA-4190D
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.
To evaluate the power of an installation it is not strictly necessary to use the voltage sensor. 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. In addition the combination of a voltage sensor with a CT sensor will provide the direction of power (import/export).
The RPICT series do not need any extra PSU. The power from the Raspberrypi is used from the GPIO. Only the raspberrypi needs to be powered as normal.
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 a Json request.
- Using Emonhub tool from Emoncms.
- Using a Python scrypt.
- Using Influxdb.
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.
As an example the output from the RPICT3T1 adaptor board will be in the format below. power in kw. temperature in deg celsius.
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
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
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_v1.0.0.deb sudo dpkg -i emonwrt3_rpi_armhf_v1.0.0.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).
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
If you are using this option then you should download the emoonpi image from this link below.
Use this image for the raspberrypi. Then modify the emonhub configuration as indicated on the board specific page.
Delete or backup the entire content of Emonhub configuration and replace with this one below.
[hub] ### 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) [interfacers] [[SerialDirect]] Type = EmonHubSerialInterfacer [[[init_settings]]] com_port = /dev/ttyAMA0 com_baud = 38400 [[[runtimesettings]]] pubchannels = ToEmonCMS, [[emoncmsorg]] Type = EmonHubEmoncmsHTTPInterfacer [[[init_settings]]] [[[runtimesettings]]] 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 [nodes] [] nodename = my_RPICT7V1 [[[rx]]] 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. Also modify the [] entry as needed. See board specific page for this.
Using Emonhub format - Raspbian image
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.
Using CSV and forwarding the data
The CSV format can be used and forwarded to a remote Emoncms server. Typically emoncms.org. A script would be used for this purpose.
We are proposing a basic script template which can be installed as below.
wget lechacal.com/RPICT/tools/lcl-Emoncms-gateway.py.zip unzip lcl-Emoncms-gateway.py.zip wget lechacal.com/RPICT/tools/gateway.conf
Edit the gateway.conf file to reflect your own setting. Content will be self explanatory.
Insert the RPICT and run
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.
#!/usr/bin/python import serial ser = serial.Serial('/dev/ttyAMA0', 38400) try: while 1: response = ser.readline() z = response.split(" ") if len(z)>=3: print "Power 1: %s Watts" % z print "Power 2: %s Watts" % z print "Power 3: %s Watts" % z print "Temperature: %s Degrees" % z[:-2] except KeyboardInterrupt: ser.close()
The above example is for the RPICT3T1 board. If using a different RPICT refer to the page of that particular board.
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 and avail them. One then need a graphing package to view the data. Influxdata proposes Chronograf but Grafana can be used too.
We are giving a basic starting script here Example Using InfluxDB.
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.
[csv_forward] 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
The onboard microcontroller can be re-programmed using the Arduino IDE software and an AVR programmer.
There is no need to reflash the microcontroller if you wish to change parameters for the following boards: RPICT7V1 version 2, RPICT4V3 version 2, RPICT8, RPICT3T1, RPICT3V1, RPICT4T4.
For other type of boards such as RPICT7V1 model 1, RPICT4V3 model 1 the only way to modify parameters is to modify the sketch and upload it to the microcontroller. This would applies for changing output format (csv/emoncms) or calibration values.
RPICT4T4, RPICT3V1, RPICT3T1, RPICT4V3 version1
This link is a tutorial to upload Arduino sketches to the Attiny84. .