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  • RE: Device Isolation and Stability?

    @brad

    Q1.) I tried to run multiple sensors within a single experiment cell (shared buffer solution), but have observed what I think is cross-talk between the devices (particularly when running 2 electrodes for electrodeposition). Are there any issues I'll need to consider here?

    Running multiple Rodeostats in a single cell (shared buffer) would be problematic. This issue is that the Rodeostat (and potentiostats in general) actively control the potential between the working and references electrodes using feedback. So when you have multiple Rodeostats in the same cell these feedback control systems can interfere with each other e.g. when the first Rodeostat adjusts the current sourced by its counter electrode in order to maintain the correct WE to RE potential this will effect the WE to RE potential of the second Rodeostat, and vice versa, etc. I think your best option here would be to isolate the test cells if you can.

    Q2.) I sometimes experience more noise in my experiments. I was thinking about just swapping in larger caps on the TIA but it doesn't seem to happen all the time. Another thought was that the power being supplied by my USB hub might be contributing. Any reason to worry? What's the best way to power the rodeostat externally while using USB for serial comm?

    You might try adding a USB isolator - not too expensive (~$35). Maybe something like this
    https://www.amazon.com/SMAKN-Isolator-Digital-Isolation-Industrial/dp/B00XXPO4UG

    Q3.) I see the P15, P16 (5/3.3V jumpers) next to the expansion headers as one option. However, I assume I would need to somehow physically disable the USB-provided +5V power away from the board?

    It is possible to externally power the Rodeostat, but doing so requires requires cutting a small trace on the underside of the teensy 3.2. This documented on the PJRC website https://www.pjrc.com/teensy/teensy31.html See the images (further down the page) showing the underside of the teensy 3.0, 3.1 and 3.2. In the upper right corner of the board there is the trace which needs to be cut - there is an arrow which points to the trace and callout the describes cutting in e.g. "Cut to separate VIN from VUSB ... etc.".

    posted in Rodeostat
  • RE: Setup and drivers - windows

    @KarlHaxthausen

    Yes the Rodeostat (and teensy 3.2) should work with windows 7. However, with windows 7 you will need to install a driver for the teensy 3.2. There are two ways to do this.

    1.) You can directly install the serial driver which can be download from here https://www.pjrc.com/teensy/serial_install.exe

    This would be the option you want if you just wish to access the device from the windows 7 computer.

    2.) You can download/install the Arduino IDE and then install the Teensyduino add-on. Instructions for doing this can be found here https://www.pjrc.com/teensy/td_download.html

    This will give you a development environment which will allow you to program the firmware on the teensy and would be the option you want if you wish to customize the firmware on the teensy in some way.

    posted in Rodeostat
  • RE: Anyone at the store?

    @mariana

    Hi Mariana,

    In response to your questions.

    Q. Is Rodeostat ready for use? Do I have to do something to make it operational?

    It is ready to use. The teensy 3.2 on the Rodeostat comes pre-programmed with the potentiostat firmware. Software is available for the host PC in the form of a Python library and a web app.

    Q. What accessories (if any) does one need to work with Rodeostat? (Assume I have reference electrode and some ugly, home made three-electrode cell).

    That should be sufficient. The Rodeostat comes with cables for connecting to the electrodes. It also in includes a 50k dummy cell for testing the device.

    Q. Is the software for Rodeostat paid or free?

    The Rodeostat firmware and software are both open source and free. The source for the firmware and software are available in projects repository on bitbucket here https://bitbucket.org/iorodeo/potentiostat/src The teensy 3.2 comes pre-programmed with the device firmware.

    Q Is this software available for Linux (Debian or Ubuntu/Xubuntu)?

    Yes. There is a Python library and a web app. Both will work on linux

    Python library: http://stuff.iorodeo.com/docs/potentiostat/
    Web App: https://blog.iorodeo.com/rodeostat-software/

    Q. What are Rodeostat current ranges?

    The Rodeostat has four current ranges +/- 1uA, +/-10uA, +/-100uA and +/-1000uA

    Q. What will be the price for delivery of Rodeostat from your store location to my country?

    You can get the price + shipping costs from our online store during the checkout procedure https://iorodeo.com/collections/cheapstat-open-source-potentiostat/products/potentiostat-shield

    Q. If I buy Rodeostat, do I have to pay VAT and customs?

    Yes.

    posted in Online store and Shipping
  • RE: Absurdly high currents in CV

    @xilophant

    You should get the best current measurement by selecting the smallest current range which will encompass your data.

    In this case the sample rate just determines the rate at which samples are collected and sent to the host PC i.e. the time step between samples. So the scan rate (V/s) is independent from the sample rate. The scan rate is set via the 'amplitude' and the 'period' parameters as follows scan rate = 4 x amplitude/period.

    You might be able to reduce the noise by taking advantage of signal averaging. You could do this by sampling at a higher rate (while maintaining the same scan rate) and then lowpass filtering the data. For example you could collect data sampling at 100 - 200Hz. And then after collecting the data lowpass filter the data to reduce the noise - maybe using a zero-phase forward-backward such as filtfilt
    https://docs.scipy.org/doc/scipy-0.18.1/reference/generated/scipy.signal.filtfilt.html
    https://www.mathworks.com/help/signal/ref/filtfilt.html

    posted in Rodeostat
  • RE: Absurdly high currents in CV

    @xilophant

    I'm wondering if it is possible that the CE and RE are being swapped? This could happen if the card orientation is not correct. Could you upload an image or two of your setup including an image card inserted into the electrode adapter?

    posted in Rodeostat
  • RE: Expansion of Rodeostat via Multiplexing

    @jbrenner

    This is a very interesting idea - thanks for sending me a link to the paper. I think this would be a great way to expand the capabilities of the Rodeostat. Perhaps the quickest and cheapest way to try this with the Rodeostat would be be make a little external expansion board which implements the make-before-break multiplexing. The expansion board could connect the Rodeostat's K1 header for the working, counter and reference electrode connections and to the DIO header "P14" for power, ground and digital control signals. I think this would be a pretty easy expansion board to make as there are only a few components required. This way we could test the idea without too much new hardware. I think I will definitely have a go at designing this expansion board. I will send you a schematic when I have something ready.

    posted in Rodeostat
  • RE: Supporting a SD card

    @AnandSingh

    Unfortunately, I don't know of any easy way to do this. There is a little flash chip (IC4) which is there to provide external memory which isn't actually used at all. It uses an SPI interface - like and SD card. If you don't include this chip you might be able to hack in and SD card in its place. Connecting wires to the pads maybe - it would be a bit dicey though. You would also have to modify the firmware to read/write to the SD card.

    posted in Cheapstat Potentiostat
  • RE: Capacitor in dummy cell

    @Rodeo_First

    The basic configuration for the dummy cell is just uses a single resistor. The PCB was designed to accommodate additional configurations e.g. a capacitor can be added to create dummy cells with different (dynamic) behavior.

    posted in Online store and Shipping
  • RE: Determining voltage supplied to CheapStat in CV

    @AheliGhosh

    The Cheapstat is a feedback device - running a control loop - so it won't really work correctly without something connected to it. In general it is trying to control the voltage between the working and reference electrodes via the counter electrode.

    You might start by using a simple dummy cell consisting of a single resistor. Connect both the reference and counter electrodes to one end of the resistor and working electrode to the other end of the resistor. Then maybe try a simple test such as a linear sweep or cyclic voltammetry. Select the resistor so that the currents are with the measurement range e.g. 50K might be a good choice for the +/- 50uA range. Measure the voltage across the resistor. If you are using a single ended input on the DAQ card (or oscilloscope) make sure to connect the ground to the working electrode and the probe to the counter/reference electrode.

    In general the Cheapstat is not capable of a full -1.5V to 1.5V swing. The actual range is more like -0.8 Vto 1.6V. Below -0.8V the output is nonlinear.

    posted in Cheapstat Potentiostat
  • RE: Software installation troubles

    @Will-Dickson

    If you want to install the software from source you can get some prebuilt wheel packages for windows here https://www.lfd.uci.edu/~gohlke/pythonlibs/#pyqt4

    Note, the colorimeter software only supports python 2.7 at this time. So you will want to have python 2.7 installed and you will want a version of PyQt4 with cp=27 in the name.

    posted in Colorimeter