CheapStat is an open source potentiostat designed by Aaron Rowe, Andrew Bonham, Kevin Plaxco and colleagues at University of Califonia Santa Barbara (UCSB). CheapStat designs along with educational applications and sample data are outlined in the 2011 manuscript "CheapStat: An Open-Source, "Do-It-Yourself" Potentiostat for Analytical and Educational Applications". Instructions for building a CheapStat along with the design files and firmware and published on the UCSB website at http://web.chem.ucsb.edu/~kwp/cheapstat/. The cost of making a CheapStat device is under $100 -- significantly less than the cost of commercial potentiostat instuments which can cost thousands of dollars. This low-cost instrument can be used in many different aspects of analytical chemistry research and education.
We recently made a set of ten CheapStat potentiostats for an environmental science project monitoring the LA river (also see: Citizen Science at LA Makerspace). The purpose of this Blog Post is just to share some of our notes and images from the build.
To make the CheapStat PCB, we used the Eagle files and BOM downloaded from the CheapStat website. The only modification we made to the PCB was to add some additional component notation and text to the silkscreen to aid in PCB assembly. The PCBs were ordered from iTead Studio. We used the original BOM from the design file download, with three substitutions (see modified BOM). The modified Eagle files, Gerber files for this order and the modified BOM are on our CheapStat repository on Bitbucket. The boards were assembled manually using a reflow oven for the surface mount components.
As described in the original design, the enclosure used is an easily machined/drilled Hammond enclosure (Digikey part # HM869-ND). To machine the holes we used our TAIG 2027ER CNC mini-mill. Each enclosure has custom holes for the LCD Display, joystick button, electrodes, USB and battery switch. Design files (gcode programs) for cutting the enclosure can also be downloaded from the project repository on Bitbucket.
For the electrodes we used 12" long test leads with alligator clips, as shown in the original CheapStat. We used packs of 10 multi-colored leads from Marlin P Jones (Part # 3569 TE) although you can get these from many places including AdaFruit and Sparkfun. We cut off an alligator clip from one end of the green, red and yellow leads and soldered these directly to the board.
Green lead = Working electrode; Yellow lead = Reference electode; Red lead = Counter electrode.
Once the electrodes were soldered onto the board, the PCBs were mounted into the enclosure using 3 x 1/4" long 4-40 screws. The battery and switch were also assembled into the case as shown in the images below.
We are currently looking into either purchasing or making the electrodes including the Ag/AgCl reference electrode, and using the potentiostat in some test experiments, such as the ones described in the original 2011 publication.