Electrochemistry
 
                             ----  NOTICE ----- 

March 2022:
We are currently sold out of the Wheestat Model 7 Circuit boards.
We hope to have a new hardware design available by summer 2023.
Prototyping for the new instrument is almost complete although sourcing components during the pandemic may delay production.  It is unclear when component supplies will be back to pre-2020 levels.
Contact me for updates

Open source potentiostat for education, research and environmental monitoring

 

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 annodic stripping 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 instruments?

To start with, we plan to abandon the Texas Instruments microcontroller environment that we have been using in favor of the Arduino compatible Teensy 4.0.  We are doing this to make the instrument ammenible to hacking by the larger Arduino using community. The instrument will also employ an on board DAC (rather than relying on pwm signals to generate voltages) and a 16 bit A to D converter.

This is the WheeStat.  We offer the WheeStat fully assembled.

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 +/- 5 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. 

What will the new instruments cost?

While we make every effort to minimize the cost of our instruments, the new models will incorporate higher cost components than the model 7 and we anticipate final prices for the 40 and 240 mA models will be around $200 and $260 USD, respectively.

When will the new instruments be available?

Once the global supply chain issues currently facing the semiconductor industry are resolved, we plan to place a small order for circuit boards.  After that, it will be a few weeks before they are manufactured and received at our NC place of business.

Supported Experiments:

Cycic Voltammetry (CV)

Linear Sweep Voltammetry

Differential Pulse Voltammetry (DPV)

Annodic and Cathodic Stripping Voltammetry

Chronoamperommetry (one and two step)

Repetative CV and DPV expeiments

Cyclic Square Wave Voltammetry

 

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 excell (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 functionallity?  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 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 $13 piece of hardware from your choice of electronics vendors (Texas Instruments, 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. 

 

KITS.

 

Kits are now available.  Kit assembly is described here for the 5 series and here for the 7 series.  They contain everything needed to put together a fully fuctional potentiostat.  Let us know if you need materials to make a set of cheap electrodes. Instructions for asssembling a working reference electrode are here and here.    All surface mount components come soldered in place.  Minimal soldering required:  wires to clips, wires to circuit board, headers to circuit board.  That is it.  Twenty six joints total.

Current code is provided on a usb flash drive.