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Measuring reaction rates.

 

To the left is one of our Rapid mixing apparatus prototypes.  This apparatus is designed for measuring chemical or biochemical reaction kinetics.  The prototype drives two syringes that mix reactants which are introduced to a flow cell for spectral analysis.  We have built prototypes with one or two motors.   Prototypes use servo controlled valves to route solution from reservoir to syringes or from syringes to flow cell.

 

The photo below shows an early Z-geometry flow cell.  Solution enters and leaves through standard 1/4" x 28  fittings.  UV-vis absorance is monitored using commercial fiber optic spectrometer and optics.

 

 

 

Microtiter Plate Reader.

 

We are working to develop an optical reader for 96 well microtiter plates.  The figure to the left shows our current setup based on our 3d printed spectrometer.  We have also developed hardware for spectrometers that use fiber optics.  In the figure, you see the plate in the foreground that moves along a track in the Y-direction.  The spectrometer is mounted on 6 mm rails and moves in the X-direction.  The light is provided by one of 8 white leds arrayed along the X-axis, below the spectrometer. 

 

The spectrometer, leds, and xy stage are all controlled by a Teensy 4.1 microcontroller board (figure on lower left).  Incorporation of TMC2209 stepper motor drivers allows sensorless homing, eliminating the need for end stop switches.

I'm going to get back to this.  Right now, we don't have the software refined for the motor drivers and have not really started work on the user interface.

 

 

Isolated Potentiostat for Electrochemical Monitoring of Capillary Electrophoresis.

 

The photo on the upper right shows an instrument we built for a customer who needed an electrochemical detector for capillary electrophoresis.  The instrument needs to be isolated from other instruments / computers / power sources, so we incorporated a raspberry pi zero 2w and powered it using a 7 amp hour, 12 volt sla battery.  The instrument communicates with a host computer over WiFi. 

 

 

WHAT'S UP?

CURRENT PROJECTS:

If you would like me to put more effort into one of these projects, please send an email telling me which one.

 

The WheeStat Potentiostat.

After years of slow development, we finally have our new model in stock.  The Pico 2.1 boasts a number of design improvements and can source +/- 40 mA. We are working on a high current module that will increase the current output.

 

Spectroscopy Projects.

The spectrometer is coming along.  This is a project that deserves more attention than I have been giving it.  We recently found out that integration periods are limited by the software to about 56 ms or less.  The issue has to do with rolling over a 16 bit counter.  While the 56 ms limitation should not affect most applications, there are others (perhaps astronomical applications) may require longer integration times.  We are working on this and I think I have it fixed in new firmware.  If this is something you are concerned about, contact me at my gmail address and I will get back to you.

I began work on a microtiter plate reader based on our spectrometer. I am looking forward to getting back to that project.

Electrocardiograph (ECG, also called EKG).

This seems like something that might be worthwhile.  While I have no plan to go through the paperwork to get FDA approval, there are a lot of people in the world who I think would benefit from the availability of low cost medical devices, especially in lower income countries.  I have already submitted a circuit board for fabrication.  Here is a link to the design we are starting with.  A schematic is presented on page 19.

Stuff we have done recently:

Electrochemical Detector for Capillary Electrophoresis:

  Work during summer 2020 focused on developing an isolated, battery powered potentiostat for use in capillary electrophoresis.  The instrument is based on the Raspberry Pi Zero 2W communicating over WiFi with a windows based host computer.  The Pi and attendant electronics are powered using a 12 volt lead-acid battery. I think this went rather well, but I have not heard back from our partners on this project.

Migration from Texas Instruments based microcontrollers:

I have decided that TI is just not interested in helping the Maker community.  While I feel like I could probably get them to work with me, They do not seem to play well with the community that I choose to serve.

While I have migrated our spectroscopy effort to incorporate the Arduino compatible Teensy 4.1, I am still looking at other Arduino compatible options.  Mostly, I plan to use the Raspberry Pi Pico. I plan to have our instruments contain an Arduino compatible bootloader so others in the community can modify and upload the code

 

 

 

CONTACT

4989 Tilley Creek Road

Cullowhee, NC 28723

Tel: 828-201-0233
 

 

Mail:  j6summers@gmail.com

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