The HomeLab-pH is a circuit board intended for pH measurements. The board may be used at home or professionally for a wide range of applications as monitoring of aquarium water quality, fermentation progress of beverage and wine, routine skin pH or urine pH checks. Will be useful as well at school in chemistry classes. The measured values are corrected for temperature changes by means of an included waterproof thermometer. The HomeLab-pH board is just a measuring block. It has to be assisted by an external CPU-board and corresponding software to perform the calculations. Software packages for Raspberry Pi computer, Arduino controller or ESP8266 module are freely available to download from the HomeLab-pH companion site at http://homelab.link. They give the user interface to log and visualize the measured values, as well as to calibrate the board.

When connected to Arduino the module can be controlled by the user visually at the console. Alternatively it can act as a data server for HomeLab-pH accessed by a remote machine through a special communication protocol. The user may program additional functionality using the available HomeLab_pH library for Arduino IDE.

When connected to Raspberry Pi or ESP8266 viewing the readings or calibrating is as simple as pointing a smart-phone browser to the Pi's / ESP8266's LAN address. The module can also be accessed through requests over http.

Features

Board

• Accurate and stable voltage reading ensures a resolution of 0.01 pH over the 0 – 14 pH range.
• Wide input voltage range suitable also for ORP measurements.
• A digital temperature sensor to compensate pH for temperature impact (ATC).
• Socket with Raspberry Pi compliant pinout.
• A LED and a button for user interaction.
• Supported by free software for Raspberry Pi, Arduino or ESP8266.
• Each board is tuned and tested.

Software options for ESP8266

• Browser interface to view the measured data, calibrate the system and set WiFi and connection settings.
• Connect as station or access point.
• Data may be shown on an eventually wired small display.
• Temporary unavailable - MQTT support with options also settable via the web user interface. Ready for ThingSpeak MQTT Device.
• Data may also be accessed by separate HTTP calls.
• Calibration with many options - temperature compensated data for 13 buffer solutions and an option to use the sensor’s isopotential data.

The ESP8266 software page.

Software options for Arduino

• A library for Arduino IDE.
• Simple visual interface to read and calibrate the module.
• Remote access by means of a special protocol (read and calibrate).

The Arduino software page.

Software for Raspberry Pi

• Rich visual interface with data viewing, logging, calibration and management.
• Periodic unassisted measurements.
• Access to the measured data remotely via an http call or locally at the OS console.

Visual interface for Raspberry Pi

• Simultaneous visualization of pH, temperature and voltage values.
• Accessible from every device with an installed browser.
• Manage, list and plot data from periodic unassisted measurements or points at user choice.
• Calibration with many options - temperature compensated data for 13 buffer solutions and an option to use the sensor’s isopotential data.

The Raspberry Pi software page.

Board specification

• supply voltage: 3.3 to 5 V
• input voltage range: -900 mV ÷ 2048 mV
• measured voltage inaccuracy: max 0.1% (but not less than 0.13 mV)
• pH inaccuracy** (temperature adjusted): pH 4 to 10: not more than 0.03 pH; pH 2 to 12: not more than 0.05 pH
• overall dimensions, W:H:D: 57 : 23 : 36 mm (2.2 : 0.91 : 1.4 in)
• board dimensions, W:D: 56 : 20 mm (2.20 : 0.79 in)

**The inaccuracy of the measurement depends on the precision of the performed calibration. The specified value is valid for 2-point calibration where the buffers' inaccuracy is not greater than 0.02 pH units and their temperature difference with the sample is less than 5°C. If calibration buffers of ± 0.01 pH are used, the inaccuracy of the measured pH value may be even lower.

Temperature sensor

• response time at 90%: typically about 15 s, max 25 s (stirred water)
• inaccuracy: not more than 0.5°C ( 0.9°F )
• working range: 0 ÷ 85°C (32 ÷ 185°F)
• tip diameter: ø 6 mm
• cable length: about 1 m ( 3'3" ); 2.5 m is optional

Optional HomeLab-Isol module

Immersed electrical appliances (e.g. aquarium pumps) may influence the measured pH value due to the high impedance of the pH-probe. The HomeLab-Isol module effectively protects the pH-module's digital and power lines from the interfering direct currents.

Find more information at http://homelab.link/ph/meter/isolated/.

What is in the box?

(shown at one of the pictures above)

• HomeLab-pH module
• digital temperature sensor
• mounting set of 2 spacers (12 mm) and 4 screws (M2.5)
• leaflet containing mounting and usage instructions

Additionally when the optional isolator module is also purchased:

• HomeLab-Isol module
• additional long spacer (25 mm) and a nut

Attention: a combination pH-probe is not included.

A tracking number is provided.

More add-on options are described below.

Optional shielded display

The HomeLab Shielded Display is a small OLED display with transparent acrylic shield in front to protect from dust or spills. It comes also with a short connection cable and with some screws to fix it to a front panel of a box. HomeLab software support for this display is currently available only for ESP8266 modules.

More info here.

Optional stand for Raspberry Pi Zero

A special stand is available if Raspberry Pi Zero is to be used as a computing unit. The stand is used to conveniently harbour in one place all the circuit boards involved. May be placed horizontally on a surface or hanged vertically.

The plates are made of plexiglass while the pillars are of polyamide. There is also a set of a small connector board and a short ribbon cable to link the Pi to the module/s. All elements come in a separate box. See what is inside.

More pictures here.

Optional Rainbow Cable Set

A rainbow cable set to connect the modules to male pin headers of controllers like Arduino Nano or Raspberry Pi is provided. The cable wires are colour coded to facilitate the connection work. The cable is 18 cm (7 in) long.

More info here.