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Electrochemistry

January 2024:
Our new hardware design will be available May 2024.

We are finishing up prototyping, updating the graphic user interface and re-writing the firmware to make it Arduino compatible. The new instrument will incorporate the Raspberry Pi Pico microcontroller board.  It will have a greater current capacity, lower noise, and greater voltage accuracy.
 
 

The  WheeStat is a computer driven three electrode potentiostat, an instrument that measures electric current exchanged between electrodes and chemicals in solution.  

It was designed for teaching electrochemistry and quantitative analysis.  It supports a variety of experiments including cyclic voltammetry and differential pulse voltammetry.

 
What's it do?

The WheeStat is capable of measuring concentrations of trace metal ions in water, including lead, arsenic and mercury.

For more information, visit the WheeStat user's manual at the link below

 

How will the new instrument differ from the older WheeStats?

To start with, we plan to abandon the Texas Instruments microcontroller environment that we have been using in favor of the Arduino compatible Raspberry Pi Pico.  We are doing this to make the instrument amenable to hacking by the larger Arduino using community. The instrument will also employ a digital to analog converter (DAC) rather than relying on pwm signals to generate voltages.

This is the WheeStat.  We offer the WheeStat fully assembled with software installed and a Windows compatible graphic user interface provided on a usb memory stick.  The 40 mA potentiostat is powered from your computer over usb. We are also developing a 240 mA instrument that will be powered by an external AC to DC adapter. 

Supported Experiments:

Cyclic Voltammetry (CV)

Linear Sweep Voltammetry

Differential Pulse Voltammetry (DPV)

Anodic and Cathodic Stripping Voltammetry

Chronoamperommetry (one and two step)

Repetitive CV and DPV experiments

Cyclic Square Wave Voltammetry

Normal Pulse Voltammetry

Electrical Attributes:

Working electrode voltage range:  +4.10 volts to -4.10 volts

Counter electrode voltage range:  +12 to -12 volts

Standard voltage step: 10 mV

Theoretical minimum voltage step: 2 uV

Standard current limits: +40 to -40 mA

Extended current limits (requires hardware upgrade): +240 to -240 mA
Maximum measurement rate: 120 data points / s

Standard measurement precision:  12 bits (1/4095)

Prices:

40 mA version:   $200 USD plus shipping

240 mA version:  $260 USD plus shipping

Our most frequent request from potential customers has been for an instrument capable of sourcing larger electric currents. The current version of our potentiostat (Model 7) is limited to +/- 7 mA. While the lower current of the Model 7 is appropriate for teaching and for many analytical applications, other applications, such as electrochemical synthesis require greater currents.

We are working on two prototypes.  The first is designed to source at least +/- 40 mA.  The second is designed to source up to 240 mA. Both will run +/- 4.1 volts on the working electrode with a compliance voltage of +/-12 volts.  The image to the right is a screenshot showing a recent test of the first prototype.  In this test, the instrument was able to establish ~+/- 4 volts across a 20 ohm test resistor.  While the power supply in this instrument was rated to supply 42 mA of current at +/- 12 volts, this data shows the instrument sourcing up to ~+/- 75 mA. 

Availability

We hope to place a small order for circuit boards in February 2024.  After that, it will be a few weeks before they are manufactured and received at our NC place of business.

Software.

The microcontroller that drives the new WheeStat comes loaded with software written in Arduino.  

The WheeStat comes with our Graphic User Interface loaded on a USB flash drive. The GUI comes as an executable program for Windows 32 and 64 bit computers as well as source code written in the program Processing.  At this point, we do not have the GUI application for Mac.  We believe that the Mac App for OSX can be generated relatively easily (see this video).  All experimental parameters are adjusted from your computer using our GUI.  Data are displayed in real time on the GUI chart.  Sequential experiments can be overlayed on the GUI chart.  Once collected, data can be saved as CSV files and opened in excel (or another spreadsheet program).  

All software is open source.  Future updates can be downloaded for free from our GitHub site.

 

Hacking the WheeStat.

Want additional functionality?  Have some unique experiment that you want to run?  No problem.  The programming languages are simple to learn and you will have the source code.  Even if you turn your instrument into a brick, it can probably be brought back to life by reinstalling the original code.   If you fry the electronics, the odds are that you can fix it by buying a cheap piece of hardware from your choice of electronics vendors (Mouser or Digikey)

Electrodes.

The WheeStat does not come with electrodes.  These need to be supplied from another source.  We note that graphite pencil lead may be used for the working and counter electrodes (black and red leads, respectively) and a Ag/AgCl electrode is recommended for the reference (green lead). Here is a link to a page that will tell you how to make a low cost Ag/AgCl electrode. 

 

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