Help with myoware cable shield connections

Sensors Biometrics
1

Hi!

I’ve started my first fun project with Arduino, so I’m a complete beginner. Excuse me if I ask stupid questions.

I bought two myoware modules, the muscle sensor (https://www.sparkfun.com/products/13723) and the myoware cable shield (https://www.sparkfun.com/products/14109). I’d like to use the electrodes of the sensor cable (https://www.sparkfun.com/products/12970) to read three different signals.

I understand I need to use the cable shield with the electrode/sensor cable.

What I don’t understand, also after reading a few times the documentation (https://learn.sparkfun.com/tutorials/my … sensor-kit and the pdf connections guide) is:

  1. whether the cable shield (14109) needs the muscle sensor (13723) to even work. My assumption is yes.

  2. how to connect 14109 with 13723

About 2) I tried connecting together the two modules one on top of the other, with the +, -, SIG pins of each module connected with a 3 pin header and the R, E, M pins also connected.

This is not working though, and I have no idea why. The R, E, M pins seem to not have any valid readings. The pins are connected to the analog inputs, just in case. If I look at the SIG pin, I get a good reading. However, the SIG pin is attached to the builtin metal “pads” of the muscle sensor (part 13723).

In short, how do I connect the sensor cable shield and the 3 electrode sensor cable to get the three R,E,M readings?

Thanks,

2

Hi cs.

whether the cable shield (14109) needs the muscle sensor (13723) to even work. My assumption is yes.

Yes, the Myoware is what actually is doing the work. The cable shield just provides a way to connect the cable to the Myoware.

how to connect 14109 with 13723

OK, you're going to need a few parts and you're also going to need to solder some pins in place to make this work.

Here’s what you need:

  • - 1x [[Break Away Headers - Straight](https://www.sparkfun.com/products/116)
  • - 3x [[Stackable Header - 3 Pin (Female, 0.1")](https://www.sparkfun.com/products/13875)
    • [/list]

    Now you’re going to want to dry fit everything before soldering, but take the straight breakaway headers and snap off three 3 pin sections. Those will go onto the Myoware like so:

    first.jpg

    Now take the three 3 pin stackable headers and they go on the cable shield like so:

    second.jpg

    A side view would look something like this:

    third.jpg

    Check to make sure everything fits correctly, then solder the pins to the board and you should be all set!](Stackable Header - 3 Pin (Female, 0.1") - PRT-13875 - SparkFun Electronics)](Break Away Headers - Straight - PRT-00116 - SparkFun Electronics)

    3

    Thanks so much for the clear and detailed explanation. I believed the raw, shield and GND on the side were not needed but it seems they are. I will try and report. Thanks!

    4

    Technically they are not needed, but having them connected helps the two boards stay physically connected together, and connecting the grounds helps keep extraneous RF and electrical noise out of the Myoware.

    Plus, in the future if you ever use other shields, the pins are already there. :slight_smile:

    5

    I think I hooked up the shield correctly now.

    While I can tap the main muscle sensor shield and clearly see the levels change,

    I can’t do the same thing (reading any of the R,E,M terminals) connected to the electrodes from the sensor cable (https://www.sparkfun.com/products/12970).

    If I’m testing the R terminal f.ex., I’m always reading the same value (f.ex. 479). It barely changes. I can see 478 or 480, but otherwise no big change like with the signal offered by the muscle sensor itself (SIG pin).

    If I disconnect the electrode from the R terminal, then I get random oscillating values. From that, I concluded that the wiring is correct and the signal is picked up by the electrodes.

    What I ultimately want to do is to read electrical signals from a plant, so I was thinking of positioning the pads on the plant leaves.

    Do I need to adjust the gain perhaps?

    Would I need a different type of electrode/pad for that application?

    Sorry for the confused questions. I’m just starting with this. It’s all new.

    6

    I’m pretty sure this won’t work on a plant, but should work great on a bicep on a human.

    Be very careful adjusting the gain control, if you turn it too far it will break and the board won’t work anymore.