This is the Hardware Repo for LeoPhi (EAGLE Files)
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Welcome To: LeoPhi Hardware Repo!!

Note: This is for the LeoPhi Hardware Version 2.2 Branch

LeoPhi Hardware Design Files in EAGLE. Not much to say, there are some custom parts will add Library after I clean it up!

Schematic Info

Basic schematic is split into sections
  • Charge Pump section
  • Analog Front End - pH gain and offset stages
  • uC controller subsection
  • reverse voltage protection
  • add addition Atmega32u4-Mu IC to account for chip shortages

Board Layout Info

Form Factor based on Dangerous Prototypes SoB 50mmx50mm PCB size
  • USB and BNC on same side to allow punch out on Front Panels
  • Guard ring on pH input stage, care must be taken in layout here
  • Leonardo Digital Header (Pin matching)
  • Leonardo Analog Header (Pin matching)
  • add addition Atmega32u4-Mu IC to account for chip shortages


Just a quick list of current issues
  • Gain may need a bit of boosting (33K instead of 47K)?
  • Silkscreen is small and hard to read in some portions
  • ESD protection on USB is on the TODO list
  • Auto selectable voltage similar to Arduino boards (USB, while 3.3v powered)


Reading pH just got a bit easier

With Arduino1.0.2 and up how the Leonardo is reset was changed and with the popularity of the LeoPhi platform I though it would be a good idea to update the hardware and bring the bootloader up to the newest version.

As before reading pH has never been easier, and with the new hardware version so it augmenting LeoPhi! All Standard Leonardo pins are brought out via the Digital Header and Analog header!

Simply plug in LeoPhi via a USB port, point you favorite Serial Port monitor to LeoPhis port and off you go! LeoPhi even works on openWRT flashed routers for pH readings over Wifi!

Please see LeoPhi's Project page for more information! Basic Usage

Usage of LeoPhi is very easy, with on board USB a fully CDC compatible bootloader (modified leonardo) all you need to do is plug it in and send some serial commands! Send an S to calibrate to ph 7 solution, F to calibrate to 4 an R to read and etc...

There are 2 serial ports one for the USB and one is the hardware serial port(Tx,Rx), this makes it useful as a USB to serial converter as well, but also means that the proper port must be select for use in any project. For example a Raspberry pie could interface LeoPhi(carefull on levels) over USB serial while the same data is dumped over the Hardware Serial to another Arduino. An I2C slave example code is also implemented which uses some of the same commands and shows how to easily implement a pH sensor with an I2C interface!

####Some of the commands are:

  • C : Continuous Read Mode: Dump readings and data every second
  • R : Single pH reading: response "pH: XX.XX" where XX.XX is the pH
  • E : Exit continuous read mode
  • S : set pH7 Calibration point
  • F : set pH4 Calibration point: also recalcs probe slope and saves settings to EEPROM
  • T : set pH10 Calibration point: also recalcs probe slope and saves settings to EEPROM
  • X : restore settings to default and ideal probe conditions

License Info

Creative Commons License
LeoPhi by Ryan Edwards, Sparky's Widgets is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Based on a work at