OK, I will have a look and get back to you.
Posts made by Will Dickson
RE: freq += 500000/dt. why??
In this case we are measuring the frequency of the pulses coming from the light sensor. The frequency of the pulses produced by the sensor is proportional to the light intensity. The pulses have a 50% duty cycle - so the pulses are high 50% of the time and low 50% of the time. The dt value returned from the pulseIn function on line 34 of ColorSensor.cpp
dt = pulseIn(FO, HIGH, pulseInWait);
returns the time the pulse is high in microseconds. The period the pulses coming from the sensor (in microseconds) is then 2*dt. This comes from the fact that we have a 50% duty cycle - i.e. one full cycle consists of the pulse being high for dt (us) and then low for dt (us). So we have period_us = 2*dt. To convert the period to seconds we divide by 1,000,000 which gives period_s = period_us/1000000. Replacing period_us with 2*dt we get the period in seconds as period_s = (2*dt)/1000000 = dt/500000. Finally, we want the frequency (in Hz) which is freq _hz = 1/period_s = (2*dt)/1000000 = 500000/dt.
RE: Cannot connect to Rodeostat with web app software
It looks like your Rodeostat is connecting, but then the software is not receiving the expected json responses back from teensy. This is usually the case when something is wrong with the firmware - e.g. it has been overwritten (teensy reprogrammed), or corrupted, etc. I would try reprogramming the firmware on the teensy,
Instructions for re-programming the Rodeo firmware on the teensy 3.2
2.) Download the latest version of the iorodeo potentiostat repository https://bitbucket.org/iorodeo/potentiostat The firmware - which you will use to re-program the teensy 3.2 - is located in the "firmware" sub-directory.
3.) Open the Arduino IDE and go to "File -> Preferences" and set the "sketchbook" location to the "firmware" sub-directory mentioned in step 2. Then restart the Arduino IDE - this step is important. You are doing this so that the IDE can find the "firmware/libraries/potentiostat" library which is the library used by the Rodeostat. The restart in necessary as otherwise the IDE won't find the library.
4.) Re-open the Arduino IDE. Go to the "Tools" menu and set the following:
- Board = "Teensy 3.2/3.1"
- USB Type = "Serial"
- CPU Speed = "72MHz"
- Port = the USB/Serial port associated with the Teensy 3.2.
- Optimize = "FAST"
Note, the "FASTER" setting won't work due an issue with the (older version) ArduinoJson library used by the firmware. This is fixed in the next version of the firmware.
Note, on linux the port might be something like /dev/ttyACM0 or /dev/ttyACM1, etc. On Windows it might be COM1, COM2, etc. If the "Port" entry in the menu is disabled then it is possible that the teensy 3.2 has been programmed with a USB Type of something other than "Serial". In this case you shouldn't need to set the port.
5.) In the Arduino IDE open the Rodeostat firmware "potentiostat.ino" file. This file can found in the "firmware/potentiostat" sub-directory of the potentiostat repository.
6.) In the Arduino IDE build the firmware by pressing the "Verify" button in the toolbar at the top of the IDE. The "Verify" button is the one with the checkmark. If all goes well there should be no errors.
7.) In the Arduino IDE upload the firmware to the teensy 3.2 by pressing the "Upload" button in the toolbar at the top of the IDE. The "Upload" button is the one with the right arrow. If all goes well there should be no errors.
RE: Serial Output
It is possible to redirect the serial output. You would need to make minor modifications to the firmware. I think this would primarily involve changing "Serial" in SerialReceiver.cpp and SerialHandler.cpp to the new serial port. The Uno only has one hardware serial port (pins 0 and 1) which is used for USB serial, but you could use SoftwareSerial (https://www.arduino.cc/en/Reference/softwareSerial) to make any two digital pins into a serial port.
RE: Rodeostat PCB assembled and Teensy 3.2
With the assembled Rodeostat PCB (as opposed to the complete device) you have two options for connecting the teensy 3.2.
You can solder the teensy 3.2 directly into the socket on the Rodeostat PCB. This is permanent.
You can solder female headers into socket on the Rodeostat PCB. The correct headers can be found here https://sites.google.com/iorodeo.com/potentiostat/hardware, items numbers 35, 36. 37.
In addition you will need to program the teensy 3.2 with the Rodeostat firmware. This can be done with the Arduino IDE.
The assembled Rodeostat PCB doesn't come with any cables for connecting the Rodeostat to your test cell or screen printed electrodes.
Finally, you may want a dummy cell for get the Rodeostat running, tests, etc.
RE: Current signals for Dummy Cell not as expected
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 (firstname.lastname@example.org) if this is the case.
RE: Adding a relay for stirrer control
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.
RE: Cyclic voltammetric: Is it possible to include a true analog scan?
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.
RE: Amperometric i-t Curve
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.
RE: Amperometric i-t Curve
Amperometric i-t Curve
Yes, you could use the "constant voltage" test for this.