Potentiostat

Team Members: Kyle BloomerJosh GeimanLucas Bennett

Team Sponsor: Dr. Cindy HarnettTeam Mentor:Dr. Andy Dozier

Dr. Harnett's laboratory needs 15 potentiostats for her microfluidics lab

Off the shelf potentiostats range in price from $5K to $10K, which is prohibitive for an instructional lab

Harnett Lab

Commercial Potentiostat

A Potentiostat is the electronic hardware required to control a three electrode cell and run most electro-analytical experiments.

An electronic instrument that controls the voltage difference between a Working Electrode and a Reference Electrode.

It measures the current flow between the Working and Counter Electrodes.

What is a Potentiostat?

A previous potentiostat was attempted by a project team using an open source design, the Ardustat

The Ardustat was a two electrode configuration Ardustat electrical design was poorly documented,

which caused the project team to have difficulty implementing it for the project

Software design was “spaghetti code”, and it had no documentation or comments for either the firmware or the application software

Hardware used was an Arduino processor board, with a prototype “daughter board”

The team was unable to meet the project goals

History - Ardustat

Ardustat Hardware

Ardustat GUI – Connect & Setup

Ardustat GUI – Data Logging

Ardustat Code ExampleBefore Ben After Ben

Previous Project Diagram

Previous Project Test Set

An MEng student has implemented the hardware using a PCB assembly, and gotten it to work

The existing code has been reverse engineered and documented/commented

BUT the Ardustat is a two electrode configuration, and the software GUI is very limited in its capabilities

Current Status

We have found an open source, three electrode potentiostat, known as the “Cheapstat”

Cheapstat was developed by UC Santa Barbara to provide an affordable alternative to COTS potentiostats

Research

Input parameters must be set through an onboard LCD and 5-way joystick

The display is very limited◦ LCD on the Cheapstat processor “box”

Provides multiple measurement modes◦ Square Wave◦ Linear Sweep◦ Stripping◦ Cyclic Voltammetry

Cheapstat Features

Cheapstat HardwareFront Panel PCB Assembly

Joystick

To CellElectrodes

Design Goals - Hardware Design and implement a three electrode potentiostat,

based on the Cheapstat Three electrode design

Easier to use interfaces GUI on a PC No joystick

Ease of assembly and use by students, faculty, and staff PCB assembly techniques USB processor to PC interface External power sources

Full documentation of hardware Schematics Simulation results Assembly diagrams List of Materials

Develop GUI and firmware using modern software engineering techniques No spaghetti code Comment all code Provide a software library

Document all the application software and firmware Installation notes User’s Manual

Design Goals - Software

Characterize electrical performance for a typical electrochemical device

Compare electrical measurements with the existing Ardustat Two electrode vs. three electrode measurement

differences

Project Goals - Other

ProcessorDevice Under

Test(DUT)

Data/Display Management

SystemUSB

120VAC60Hz15A

Voltage Converter

System Diagram

Processor◦ Firmware

Display/Data Management System (DDMS)◦ GUI software

Power supply

Major Components

ProcessorDevice Under

Test(DUT)

Data/Display Management

SystemUSB

120VAC60Hz15A

Voltage Converter

System Diagram

Processor Requirements Capture the test configuration

Measurements to be made, ranges, etc. Execute the test using the measurements that have

been established by the operator Log and time stamp test results in NVRAM Send measurement data to Display/Data Management

System (DDMS) during test When polled by the DDMS, send the test results in CSV

format to a file on the PC

ProcessorDevice Under

Test(DUT)

Data/Display Management

SystemUSB

120VAC60Hz15A

Voltage Converter

System Diagram

Pre- test Mode Calibrate instrument Configure processor for the test to be executed

Test Mode Execute test script that was entered during Pre-Test Display results during test

Post Processing◦ Report generation

DDMS Requirements

GUI Mockup

ProcessorDevice Under

Test(DUT)

Data/Display Management

SystemUSB

120VAC60Hz15A

Voltage Converter

System Diagram

Three options are available: Wall Wart USB Battery power

Microprocessor requires 5 VDC Estimated 3 watts

Voltage Converter

Build and test Cheapstat using current design CheapStat Parts have been ordered

Research ongoing regarding firmware development environment

Software development kit to preserve schedule Test existing Ardustat

Need DUT – Chlorine Generator?

Current Status

Questions?