Can I prototype the circuit on a breadboard [resolved]
kino009
Jamaica
With some of the components reaching EOL, i was wondering if the community planned to update the BOM or design procedure.
Im trying to build this for my major project. I was wondering where to start, when it came to mind that maybe i could build the circuit piece by piece on a breadboard. is this possible?
Comments
Kino, hi. Generally using friction fit breadboard will result in a large increase in noise level, since the ADC is operating in the microvolts range.
It is possible to use an isolated usb connection instead of the RFduinos.
https://www.google.com/search?as_q=usb+connection
Oops, left the wrong link by typo, should have been this one that searches OpenBCI,
https://www.google.com/search?as_q=usb+connection&as_sitesearch=openbci.com
The way this is done, is by using a usb serial port breakout board, and usb isolator. The serial pins from the breakout are wired to the PIC 'serial1' TX, RX pins. 'serial0' was used for the RFduino route. Since RFduinos are at EOL, you can use this alternate serial port access method. Links above explain the details.
Thank you for the speedy reply,
So in regards to the breadboarding, only way to simulate the circuit is to have its pcb printed?
would that not be more costly, in both time and money in the testing and prototyping stage?
If you know of a way I could simulate the circuit or any guides that show how to build a new model please let me know
thank you
I assumed you were referring to Cyton, but I see now on your initial question you did not mention either Cyton or Ganglion. Both the radio modules used (RFduino and Simblee) are now EOL. Cyton would likely be the easier route, since the usb serial interface idea has already worked for others.
I'm not sure that you need to breadboard to simulate and test. If you look through this category, you can see that others were able to build Cyton from the PC board layout and BOM. The change for usb serial instead of RFduinos is a relatively minor adjustment, that only impacts firmware.
https://openbci.com/forum/index.php?p=/categories/build-it-yourself
Note that both Cyton and Ganglion have had careful PC board layout design considerations. For low noise microvolt sensitive signals, component placement, power and ground planes ("star grounding") need to be factored. This is another reason that a conventional (friction fit, loose random wires) breadboard is not going to perform very well.
Here is an excellent app note from Analog Devices on star grounding and noise reduction techniques for mixed signal (digital and analog) designs.
https://www.analog.com/en/analog-dialogue/articles/staying-well-grounded.html
finished reading the last link this morning.
Thank you for your help thus far, truly admirable. I have 2 more questions to clarify before I move on.
Since the EOL of RFduino, the only thing I need to change in the schematic is the removing it and replacing it with a usb connection?
Will that connection be responsible for sending the data to the computer? if so wouldn't it be a wired connection and be more susceptible to movement artifacts?
Lastly, If you know of any links of someone who has successfully made it wireless, pref Bluetooth or something similar to the rfduino where a usb was in the comp and the cyton could transmit from a pretty decent distance.
Sincerely yours,
Jermaine
You don't need to modify the Cyton PC board layout or schematic at all. For the usb serial, use one of the breakout boards available, such as,
https://www.adafruit.com/product/2264
This is then just fastened to the Cyton with foam double stick tape. Check the previously given link for the breakout they used, I think it was this one.
https://www.google.com/search?as_q=usb+connection&as_sitesearch=openbci.com
HAVE U MADE YOUR BOARD COMPLETELY ?
IS YOOUR BOARD WORKING PROPERLY ?
re: BOM. Please see previous comments on this thread. Friction fit breadboard would likely have considerable noise, since it lacks power/ground planes and "star grounding". A usb serial breakout board can provide the serial link, be sure to use a USB Isolator with it. All of this is referenced in the previous links on usb connection.
https://www.google.com/search?as_q=usb+connection&as_sitesearch=openbci.com
@arpit
I haven't completed the design as yet. Still making a few changes to the schematic