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  • RE: Current signals for Dummy Cell not as expected

    @rcbb

    Hi Rodrigo,

    There is definitely something funny going on in that first result. . I'm not sure what is causing it. I doubt that it was the firmware update. I would start with the usual things - make sure all the connections are OK and that the electrodes are connected correctly. Also, If you want to the send rodeostat back to I could have a look at. Send me an email (will@iorodeo.com) if this is the case.

    posted in Rodeostat
  • RE: Adding a relay for stirrer control

    @PJS

    On the cheapstat there aren't reallly any spare digital IOs which are conveniently available on a header or any thing like that. There are spare digital IOs on the ATXMega, e.g. PB0, PB1, PC0, PC1, etc., but the trick would be accessing them. You would have to solder a to the microcontroller pin/pad. Another option might be to the IO lines used for the SPI signals to IC4. This is a flash memory which isn't used by the current firmware. You could remove this chip and you would have four IO lines available at IC4 - CS (PD4), SI (PD5), SO (PD6) and SCK (PD7). Again you would have to solder to the pads - a pain, but at IC4 they are a bit bigger at least.

    Another option might be the Rodeostat which has 2 expansions headers P13 and P14. Between them you have 16 digital IO lines you could use plus SPI and i2c bues. Both P13 and P14 use 5x2 shrouded headers which you can connect to with a standard IDC connector.

    posted in Cheapstat Potentiostat
  • RE: Cyclic voltammetric: Is it possible to include a true analog scan?

    @amgomezma

    Unfortunately, it isn't possible to do a true linear ramp with the Rodeostat. It uses a Digital to Analog Converter (DAC) to set the analog output value and so the output will always be in discrete steps where the minimum possible step value set by the resolution of the DAC.

    posted in Rodeostat
  • RE: Amperometric i-t Curve

    @cylsky

    Yes, the current is measured as the test is run. The figure is showing the applied potential in order to illustrate the various test parameters e.g. quietTime, duration, etc.

    The worked example in the link below shows a plot of the current vs time when using the constant voltage test and a dummy cell.
    http://stuff.iorodeo.com/docs/potentiostat/examples.html#constant-voltage-voltammetry

    posted in Rodeostat
  • RE: Amperometric i-t Curve

    @cylsky said in Amperometric i-t Curve:

    Amperometric i-t Curve

    Yes, you could use the "constant voltage" test for this.

    http://stuff.iorodeo.com/docs/potentiostat/tests.html#constant-voltage

    posted in Rodeostat
  • RE: Problem in python installation

    @robotsandi

    It looks like you are using Python 3.5. This issue you are seeing is due to the differences between the Python 2 and Python 3. The colorimeter software is not yet compatible with Python 3. So in order to run it you will need to install Python 2.7 and then reinstall the colorimeter software and its dependencies.

    posted in Colorimeter
  • RE: Replicate of Ascorbate curve with other chemicals

    @Annie

    The standard dummy cell which comes with the Rodeostat consists of a single 50K Ohm resistor. When the dummy cell is attached with the cable to the Rodeostat one end of this resistor will be connected to both the counter and reference electrodes and the other end will be connected to the working electrode. The results you should get when using this dummy cell should follow Ohm's law i.e. the measured current should be I = V/R. In your images it looks like you are sweeping the voltages from about -0.6V to 1.5V - using the cyclic test?. So your measured currents should sweep from -12uA to 30uA and back again according to Ohms law. Looking at your results this seems to be what you are getting - so I would say this first test checks out. Note, when using the +/-1uA and +/-10uA current ranges some of the currents you are trying to measure during the sweep are outside of the measurement range. Thus you are seeing saturation in the measured currents i.e. the measure values can't go above or below the limits of the ranges.

    From your results with the dummy cell it looks like the Rodeostat is working correctly.

    I'm not sure what is happening with the drop sense electrodes and the Malonic/Lactic Acid. We haven't worked with the AuNP electrodes or with either of these Acids.

    A couple of things to check.

    • Make sure you are getting a good electrical connection between the screen printed electrode and the adapter. Sometimes you might need to put a thin spacer on the back of the screen electrode in order press it against the electrical connections.

    • Make sure the screen printed electrode is connected correctly - so that the counter, reference and working electrodes are connected to the proper connections.

    posted in Rodeostat
  • RE: Replicate of Ascorbate curve with other chemicals

    @Annie

    Hi Annie,

    A couple of quick questions:

    1. Do you get reasonable values when running a test using the dummy cell?

    2. Have you tried to replicate the results using ascorbate?

    posted in Rodeostat
  • RE: Clibration problem

    @robotsandi

    The light sensor used by the colorimeter is a light to frequency converter which returns the squarewave with frequency directly proportional to the light intensity. The number of samples setting (for example 500) sets the number of pulses which will used in order to measure the frequency. The period of all the pulses sampled is then averaged in order to determine the frequency (light intensity).

    posted in Colorimeter
  • RE: Add a nokia 5110 LCD Screen with colorimeter kit

    @robotsandi

    The software and firmware for the colorimeter can be found in our online repository here https://bitbucket.org/iorodeo/colorimeter/src The firmware for the Arduino is in the "firmware" sub-directory of the project. This will be what you want to modify to add you LCD display. Beyond that it is really up to you add the display you want and modify the firmware correctly.

    It looks like the nokia 5110 is 3.3V so you may require a level shifter.

    You might look at using the Adafruit PCD8544 Nokia 5110 LCD-library https://github.com/adafruit/Adafruit-PCD8544-Nokia-5110-LCD-library

    There is a tutorial here https://learn.adafruit.com/nokia-5110-3310-monochrome-lcd/testing

    posted in Colorimeter