Pressure Lab

Last Updated or created 2022-07-03

For measuring pressure in fermentation containers, I designed a pressure sensor which could be wireless connected to a fermentation container.
The sensor would transmit the values to a Raspberry which was configured as a Access Point and would store the measurements and generated graphs using Grafana.

Raspberry with RealtimeClock
RTC on raspberry

3D printed holder, designed in blender. Holds battery prints and has little handle to lift from container

Nodes config:

Esp configuration, connect with micro-usb
Flashing with linux -p /dev/ttyUSB0  write_flash 0x00000  ESP_Easy_mega-20190311_normal_ESP8266_4M.bin

Make a connection with the ESP Access point

Connect esp with a power source.
Look for a AP with ESP_Easy_0

Use password “configesp” to connect

Start you browser and enter

In wifi wizard setup select “pressurespot”
Enter password “pressurespot”

Press connect

Wait 20s and look in the raspberry logs which IP the ESP got.

Connect laptop/mobile to wifi “pressurespot”and connect

Enter found IP from ESP in your browser.

Proceed to main config

Main setting table, set the following

  • Unit name & number + append
  • SSID and WPA key pressurespot
  • Client IP block level allow all
  • Press submit

Press controller tab

Press first edit button and set following
– Protocol: domoticz http
Next set
– Controller IP :
– Toggle enabled and press submit

Resulting in:

Next we got to Hardware

I2C interface switch GPIO-4 and GPIO-5

  • GPIO – SDA: GPIO-4 (D2) change to GPIO-5 (D1)
  • GPIO – SCL: GPIO-5 (D1) change to GPIO-4 (D2)
  • Press “Submit”

Devices TAB

Press edit, and select device “Environment – BMx280” from the pulldown menu.

Next, set the following

  • Name: pressure
  • Enable on
  • I2C address : 0x76 ( Is there is no 0x76 of 0x77 .. do a i2c scan on the next tab )
  • Send to controller , mark this
  • IDX: give this the number you had given this node (this is the one you have to use in domoticz )
  • interval 10Seconds
  • and press submit

In the Devices tab, you should be able to see the sensor with the values (Temperature and pressure)

No values? Do a i2c scan and/or reboot ESP ( You can find these in the tools tab)

Tools TAB

Press I2C scan, when seeing a address like 0x76 or 0x77 use this in previous tabs.
Still nothing, even after reboot? Maybe faulty hardware?

Everything okay? Back to the config tab

We are going to set the sleep mode.
Warning ! .. when setting this it is hard to get into the config pages again.
ESP will startup, connect to wifi, send values and goes to sleep again.

At the bottom set: Sleep awake time 1 sec

Buttons on the raspberry / pressurespot

Red button :

  • Less than 3 seconds is reboot
  • Longer than 3 seconds is shut down
    • Charger can be removed, when the green light is off

Led lights on the sensors

  • Red light (R2; constant): battery is charging
  • Blue light (R1; constant): battery is full
  • Blue light (R1; constant) & red light (R2; blinking): trying to charge, but no battery connected

Add shutdown script to /etc/rc.local

python /usr/local/bin/ &


import threading, subprocess
import RPi.GPIO as GPIO
def shutdown():'sudo shutdown -h now', shell=True)
def edge_detected(pin):
    if GPIO.input(pin):
        t.cancel()'sudo reboot', shell=True)
if __name__ == '__main__':
        GPIO.setup(5, GPIO.IN)
        GPIO.add_event_detect(5, GPIO.BOTH, callback=edge_detected, bouncetime=10)
        t = threading.Timer(3.0, shutdown)
        while True:


import RPi.GPIO as GPIO
import time


import RPi.GPIO as GPIO
import time

nmcli device wifi hotspot ssid pressurespot password pressurespot







/usr/bin/ (in rc.local and crontab root user – every minute

nmcli connection show  | grep "Hotspot-1           c2c05528-63f9-44c7-93ce-264187a45086  802-11-wireless  wlan0" >/dev/null && touch /tmp/wlan || rm -f /tmp/wlan
for f in influx domoticz telegraf grafana mosquitto ; do
pgrep $f >/dev/null && touch /tmp/$f || rm -f /tmp/$f
count=$(ls  /tmp/influx /tmp/domoticz /tmp/telegraf /tmp/grafana /tmp/mosquitto /tmp/wlan | wc -l)
if [ $count -eq 6 ]  ; then
exit 0

for timer in {1..10} ; do
sleep 1

sleep 1

Rest services to be installed on Raspberry

At the moment the raspberry uses domoticz between the Mqtt broker (Mosquitto) and the database (Influx)
Data wil be displayed using grafana.

tail -f /var/log/syslog shows which ip to which ESP
DHCPACK(wlan0) cc:50:e3:c4:96:61 lab-
DHCPACK(wlan0) cc:50:e3:c4:8d:73 lab-4
DHCPACK(wlan0) cc:50:e3:c4:9b:ef lab-1

Configuring the raspberry

Install influx and grafana

First we add Influx repositories to apt:

wget -qO- | sudo apt-key add -
source /etc/os-release
echo "deb $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/influxdb.list

Update apt with the new repo & install.

sudo apt update && sudo apt install -y influxdb

Then start the influxdb service and set it to run at boot:

sudo systemctl enable influxdb --now

Again we need to add the Grafana packages to apt:

wget -q -O - | sudo apt-key add -
echo "deb stable main" | sudo tee /etc/apt/sources.list.d/grafana.list

We can now update and install the binaries:

sudo apt update && sudo apt install -y grafana

Then simply enable the service and set to run at boot:

sudo systemctl enable grafana-server.service --now

Now we can check that grafana is up by loading it in a browser: If so, you can log in with the username and password = admin and set a new admin password.

Install mosquitto

sudo apt install mosquitto mosquitto-clients

Install domoticz using below command

<code><strong>curl -sSL | sudo bash</strong></code>

Under hardware add MQTT server adress

Add virtual sensors to domoticz.

Click hardware and create virtual sensor, lab with sensornumber. Sensor type is Temp+Baro.

When looking at devices you will see the virtual devices.

Here you can see if data is coming from the ESP’s

Pushing the data into Influxdb:

Goto settings > more options > data push > influxdb

Add temperature

  • Device name: lab* (lab plus unit number)
  • Value to send: temperature
  • Target type: direct (NOTE screenshot below is wrong)
  • press add

Add barometer

  • Device name: lab* (lab plus unit number)
  • Value to send: Barometer
  • Target type: direct (NOTE screenshot below is wrong)
  • press add

Configure Grafana

Go with your browser to when connected to the rpi access point

Goto settings and data sources, add influxdb with source http://localhost:8086
Goto dashboard and create a new one.

Data source is influx, select A Barometer
And the IDX that was used in configuring the ESP
Axes: Units in millibars, above example had temperature, for both Baro and Temp in one graph.
Select null value as connected


Services in domoticz
Rpi status display
Sensor test / monitor