RPi/use/read_temperature_from_DS18x20_sensors

#

2020 06 12 + init /A

2022 03 18 + published on https://github.com/InstallAndUse/RPi /A

#

INSTALLATION:

sudo su

raspi-config, 5. interfaceing, P7 1-wire, enable, yes. reboot

ls -la /sys/bus/w1/devices/*

 lrwxrwxrwx 1 root root 0 Jun 12 12:18 /sys/bus/w1/devices/00-200000000000 -> ../../../devices/w1_bus_master1/00-200000000000
 lrwxrwxrwx 1 root root 0 Jun 12 12:18 /sys/bus/w1/devices/00-a00000000000 -> ../../../devices/w1_bus_master1/00-a00000000000
 lrwxrwxrwx 1 root root 0 Jun 12 12:13 /sys/bus/w1/devices/w1_bus_master1 -> ../../../devices/w1_bus_master1#

when sensors connected:

(connect VCC to 5V, GND to GND, DATA to TXD PIN, remember to put resistor 4.7 kOhm between VCC and DATA)

ls -la /sys/bus/w1/devices/*

 lrwxrwxrwx 1 root root 0 Jun 12 12:20 /sys/bus/w1/devices/00-600000000000 -> ../../../devices/w1_bus_master1/00-600000000000
 lrwxrwxrwx 1 root root 0 Jun 12 12:20 /sys/bus/w1/devices/00-e00000000000 -> ../../../devices/w1_bus_master1/00-e00000000000
 lrwxrwxrwx 1 root root 0 Jun 12 12:20 /sys/bus/w1/devices/10-000800e489b3 -> ../../../devices/w1_bus_master1/10-000800e489b3   <-- this is first sensor
 lrwxrwxrwx 1 root root 0 Jun 12 12:20 /sys/bus/w1/devices/10-00080280a759 -> ../../../devices/w1_bus_master1/10-00080280a759   <-- this is second sensor
 lrwxrwxrwx 1 root root 0 Jun 12 12:18 /sys/bus/w1/devices/w1_bus_master1 -> ../../../devices/w1_bus_master1#

save this script (read_ds18x20.py) and bash script (read_ds18x20.psh) to /home/pi/meter

chmod +x /home/pi/meter/* ls -la /home/pi/meter/*

check you have python installed (probabaly on RPi it is)

which python

 /usr/bin/python

eventually, run first read

root@(host):/home/pi/meter# ./read_ds18x20.py

 /sys/bus/w1/devices/10-000800e489b3;27000
 /sys/bus/w1/devices/10-00080280a759;29500#

prepare PostgreSQL database for telemetry gathering (satellite)

#

install postgres

sudo su apt install postgresql

start cluster

pg_ctlcluster 11 main start

connect to DB

su - postgres psql

create user (user is named accordingly to hostname to simplicity in future replication configuration)

CREATE USER (user) WITH PASSWORD '(pass)'; \du

create database (there is only one DB named telemetry to avoid confusion)

CREATE DATABASE telemetry; \l

grant access to (user)

GRANT ALL ON DATABASE telemetry TO (user) ; \l telemetry

connect to DB and create table

tables are named individually to keep order for replication

telemetry_hostname represents table with telemetry for hostname

\c telemetry CREATE TABLE telemetry_host(); \d \d telemetry_host

adding columns to table

it is importnant to set NOT NULL, because we do not want to keep DB clean and tidy

ALTER TABLE telemetry_host ADD COLUMN timestamp TIMESTAMPTZ PRIMARY KEY; ALTER TABLE telemetry_host ADD COLUMN sensor CHAR(64) NOT NULL; ALTER TABLE telemetry_host ADD COLUMN value INTEGER NOT NULL; \d telemetry_host

grant access on table to (user)

???

change DB credentials in shell script (user) and (pass)

nano ./read_ds18x20.sh pi@(host):~/meter $ ./read_ds18x20.py | ./read_ds18x20.sh

 INSERT 0 1
 INSERT 0 1

set peiodic check with cron (good idea to setup cron for root, because future checks will be consolidated in one place)

sudo crontab -e

 */1 * * * * /home/pi/meter/read_ds18x20.py | /home/pi/meter/read_ds18x20.sh

check that cron is working:

tail -f /var/log/syslog | grep CRON

 Jun 12 12:47:01 lab5rp41 CRON[1507]: (root) CMD (/home/pi/meter/read_ds18x20.py | /home/pi/meter/read_ds18x20.sh)
 Jun 12 12:47:04 lab5rp41 CRON[1503]: (CRON) info (No MTA installed, discarding output)#

check that entries actually written to db

psql -h (host_ip) -U (user2) -d (db) -c "SELECT * FROM telemetry_host;"

 Password for user (host):
            timestamp           | value |                              sensor
 -------------------------------+-------+------------------------------------------------------------------
  2020-06-12 08:58:36.732033+01 | 12345 | test_sensor
  2020-06-12 10:38:12.519066+01 | 27500 | /sys/bus/w1/devices/10-000800e489b3
  2020-06-12 10:38:12.68798+01  | 29000 | /sys/bus/w1/devices/10-00080280a759
  2020-06-12 10:38:47.060764+01 | 27000 | /sys/bus/w1/devices/10-000800e489b3
  2020-06-12 10:38:47.222548+01 | 28937 | /sys/bus/w1/devices/10-00080280a759
  2020-06-12 10:46:38.363432+01 | 27062 | /sys/bus/w1/devices/10-000800e489b3
  2020-06-12 10:46:38.552815+01 | 28812 | /sys/bus/w1/devices/10-00080280a759
  2020-06-12 10:47:03.880082+01 | 27687 | /sys/bus/w1/devices/10-000800e489b3
  2020-06-12 10:47:04.031554+01 | 28750 | /sys/bus/w1/devices/10-00080280a759
 (9 rows)

Books:

• Anton's bookshelf