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

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

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 had no documentation or comments for either the firmware or the application software

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

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

Two Different Potentiostat Systems

Two Electrode Potentiostat (Formally known as the “Ardustat”)

Three Electrode Potentiostat (Formally known as the “Cheapstat”)

Our project will entail the completion of both systems and comparison of test results of both systems.

Characterize electrical performance for a typical electrochemical device

Compare electrical measurements between the two systems Two electrode vs. three electrode measurement

differences Document all materials

Project Goals - Other

Three Electrode Potentiostat

Design Goals - Hardware Design and implement a three electrode

potentiostat, based on the Cheapstat Three electrode design

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

ProcessorDevice Under

Test(DUT)

Data/Display Management

SystemUSB

120VAC60Hz15A

Voltage Converter

System Diagram

Processor◦ Firmware

Display/Data Management System (DDMS)

Voltage Converter

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

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

Post Processing◦ Report generation

DDMS Requirements

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

Two Electrode Potentiostat

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

System Diagram

Display/Data Management System (DDMS)

Ardustat◦ Arduino Development Board◦ Daughtercard

Major Components

Capture Input Parameters Transmit Configuration to Arduino Development

Board Start Experiment Procedure Export Logged Data

DDMS Requirements

DDMS GUI

Capture Configuration Send Commands to Daughtercard Export Measured Data

Arduino Development Board

Arduino Development Board

Capture Measurements Send Measurements to Arduino

Development Board

Daughtercard

Daughtercard

Prepare four orange juice samples, one as a control, the other three containing the addition of exogenous ascorbic acid at 0.1,.02, and 0.3M respectively.

Prepare a working electrode using a graphite pencil “lead”.

Prepare a reference electrode using a standard Ag/AgCl electrode.

Prepare a counter electrode using a piece of platinum wiring. (This will not be used for the Two Electrode Potentiostat configuration)

Experiment

Attach the electrodes to the Potentiostat systems.

Perform a cyclic voltammetry test taken from 200 to 900 mV, with a constant current of 550 mV.

Export the data to CSV file and graph the results.

Analyze graphed results against Rowe’s results using an eye inspection test.

Experiment

Two Electrode Potentiostat

Results

Three Electrode Potentiostat

Results

Although the tests show that both systems work, the results were not as expected

Several possibilities:◦ Ag/AgCl reference electrode◦ Relay usage◦ Firmware implementation(?)◦ Chemical procedure integrity

Conclusions

Universal System◦ Verify suggested conclusion and recommendations

Two Electrode Potentiostat◦ Other modes of operation◦ Calibration settings

Three Electrode Potentiostat◦ Implement DDMS GUI

Removed joystick and LCD

Future Work

GUI Mockup

Questions?