Wireless Triggers for video stimuli

ShyamalShyamal Canada

Hello,

I'm considering using wireless manual triggers for the Cyton Daisy board with HC-12 or nRF24L01 modules. While I'm aware there might be some delays, I'm looking for suggestions on minimizing them.

The goal is to eliminate the photodiode on the screen and achieve accurate markers with minimal delay. Are these modules suitable for video stimuli, or would using the BrainFlow API for inserting markers suffice?

Thank you!

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Shyamal, hi.

    The optoisolator approach can also interface with external trigger sources, other than photodiodes.

    https://docs.openbci.com/Cyton/CytonExternal/#optoisolation

    PsychoPy users sometimes employ a usb parallel port.

    https://psychopy.org/hardware/parallelPortInstr.html

    William

  • ShyamalShyamal Canada

    Hi William,

    We intend for participants to move slightly during the experiment. However, we've observed that this movement contributes to increased noise in the data. To address this, we're minimizing movement of electrode wires and a modified board setup (holding the board still). Additionally, we are using a gel-free saline cap for this experiment. I'm curious if you have any suggestions on how to improve such experiments and reduce overall noise?

    As for the optoisolator, I'm wondering if it requires a connection between the computer and the board. It may not be the most suitable solution in this case?

    Best,
    Shyamal

  • wjcroftwjcroft Mount Shasta, CA

    @Shyamal said:
    ...
    We intend for participants to move slightly during the experiment. However, we've observed that this movement contributes to increased noise in the data. To address this, we're minimizing movement of electrode wires and a modified board setup (holding the board still).

    It is the electrode wire motion that creates the most artifact. In fact having the board co-mounted on the subject can reduce this. And using shorter wires also helps.

    Additionally, we are using a gel-free saline cap for this experiment. I'm curious if you have any suggestions on how to improve such experiments and reduce overall noise?

    I'm not suggesting modding your cap. But solutions that mount the board on the cap, head, or shoulder and use short wires from board to cap electrodes, is a common solution seen from other manufacturers. And also the Ultracortex headset.

    As for the optoisolator, I'm wondering if it requires a connection between the computer and the board. It may not be the most suitable solution in this case?

    What is the SOURCE of your trigger signal? The trigger can be connected through the optoisolator to the board.

    Regards, William

  • ShyamalShyamal Canada
    edited May 13

    It is the electrode wire motion that creates the most artifact. In fact having the board co-mounted on the subject can reduce this. And using shorter wires also helps.

    We recently bought a tool

    https://www.amazon.ca/Accessories-Release-Compatible-Session-Insta360/dp/B08R72LPNQ/

    that people wear on like a bag, usually it is used to hold a phone for taking videos. it will hold the board and then we will tape the gel-free cap electrode wires properly to it that goes toward the cap. Not sure if it will work but giving it a try. I was wondering if gel-free cap has a shorter electrode wires?

    What is the SOURCE of your trigger signal? The trigger can be connected through the optoisolator to the board.

    The souce would be the computer running our PsychoPy python script, which is also connected to the board via OpenBCI GUI or BrainFlow.

    Best,
    Shyamal

  • wjcroftwjcroft Mount Shasta, CA

    If you are using PsychoPy, then you can use their parallel port system and the optoisolator,

    https://psychopy.org/hardware/parallelPortInstr.html

  • ShyamalShyamal Canada

    The participant will step forward and backwards and they are standing approx 2 or 3 meters away from the screen and computer. We will have to connect a long wire that connects to computer parallel port to optoisolator to board. Do you think this would work?

  • wjcroftwjcroft Mount Shasta, CA

    Hmm, 6 to 10 feet sounds a bit awkward. But could work if for example the wire goes off to the subject's left or right and not forward or back. Thus avoiding tripping over it.

    Note the 'wire' is actually a wire pair. As shown.

    https://docs.openbci.com/Cyton/CytonExternal/

    I'm not sure the usb parallel port idea gives you any advantages. In fact is is slightly distorted with what you would pick up from the photodiode.

    There are things called Bluetooth switches. Might be a possibility more along your initial thread question.

    https://www.google.com/search?q=bluetooth+activated+switch

  • ShyamalShyamal Canada

    I tried using a photodiode with a long-distance setting, and it actually worked, but it does increase delays in markers. However, I believe there were constant delays due to the distance between the photodiode and the board. According to you, which option should I choose for an ERP study: a photoiode or an optoisolator?

    Since for a movie stimulus experiment, we don't want to use a photodiode or an optoisolator as we truly want portability.

  • wjcroftwjcroft Mount Shasta, CA

    You'll have to experiment yourself.

Sign In or Register to comment.