Getting Started with the MyoWare® 2.0 Muscle Sensor Ecosystem

Contributors:

Hardware Hookup

Advancer Technologies has provided a Quick Start and Advanced Guide for the MyoWare 2.0 Muscle Sensor. Feel free to check them out with this guide.

Selecting a Muscle Group

Select a muscle group to place the MyoWare 2.0 Muscle Sensor. Placement of the sensor is critical when measuring the muscle activity. You will need to connect the MID electrode to the middle of the muscle body with the END electrode lined up in the direction of the muscle length. The REF electrode will be adjacent to the muscle body.

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Advanced Guide

We'll be using the forearm as an example. You can connect the sensor to any muscle group as long as orient the sensor's electrodes with respect to the target muscle as explained above. Note that the muscle group shown in the image below are not to scale.

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Quick Start Guide

For more other muscle groups, check out the MyoWare 2.0 Advanced Guide. Make sure to zoom in on the image for a closer look at the muscle group. The positions shown in the image are approximate.

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Advanced Guide

Preparing the Skin

Note: Ensure that there is sparse or no hair on the skin where the EMG pads will stick. If necessary, remove any excess hair. Body hair can cause a poor connection and should be avoided.

Grab an alcohol swab to clean the skin where the MyoWare 2.0 Muscle Sensor will be placed. Cleaning the skin with soap can leave a residue on the skin and should be avoided.

Clean the skin where the EMG pads will stick using an alcohol swab. A cotton ball soaked in isopropyl alcohol is also sufficient to remove any oils or surface contaminants on the skin. Allow the isopropyl alcohol to evaporate before sticking the EMG pads on the skin

Note: We recommend against using the alcohol swab on the face. When cleaning the skin, a brisk wipe is sufficient. Using excessive rubbing alcohol will cause the skin to dry which may cause intermittent readings due to poor contact with the skin.

Stacking Shields

Since the shields are keyed, there's only one way to stack the boards together! Just look for the snap connector labeled as GND or REF. Align the snap connectors. Make sure the power switch is flipped to the OFF position for shields.

Stack Shields Together while Aligning the GND or REF Snap Connectors

Push down on the snap connectors using your thumb and index finger. Make sure to avoid pressing down on the built-in LiPo battery.

Connecting to a Muscle Group

Snap the EMG pads to the bottom of the MyoWare 2.0 Muscle Sensor. For users using the MyoWare 2.0 Cable Shield, you'll be snapping it to the sensor cable's snap connectors.

Peel and carefully remove the backs of the electrodes to expose the adhesive.

Attach the pads to the target muscle. In this case, we are using our right forearm.

Note: As stated in the MyoWare 2.0 Quick Start Guide, we do not recommend snapping the MyoWare 2.0 Muscle Sensor to the electrodes after they've been placed on the skin, doing so can cause bruising!

Note: The default gain should be sufficient for most applications. However, advanced users can adjust the trim pot for the ENV's output to the desired gain setting using a screwdriver. Turn the trim pot clockwise to increase the gain. Turn the trim pot counterclockwise to reduce the gain. Take care when rotating the trim pot since it can be damaged by over rotating and overuse.

Ensure that power is disconnected when stacking shields on the top side of the MyoWare 2.0 Muscle Sensor. Once everything is connected, flip the power switch to the ON position on the Power Shield or LED Shield. For users connecting the sensor to an Arduino and computer, check to make sure that your computer is not connected to the wall outlet. Then flip the power switch to the ON position on the Link Shield.

Connecting Shields to the Arduino R3 Development Board

⚡ Danger: When connecting your MyoWare 2.0 Muscle Sensor to a computer for Serial debugging, it is suggested to have a USB isolator with the MyoWare 2.0 Muscle Sensor to prevent noise in the inputs and safeguard against electrical shock when connected to a power grid (such as a computer power supply, computer docks, and external monitors connected to a wall outlet). The diagram below shows USB isolator (as shown as a blue board) between a desktop and the Arduino's USB port.

USB Isolator Connected Between Desktop and Arduino

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Quick Start Guide

If you do not have a USB isolator, try using a laptop running on battery power and ensure that you are not connecting the laptop to a wall outlet.

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Quick Start Guide

We also recommend using a wireless keyboard and mouse when programming in Arduino. The muscle sensor is sensitive enough that it can also pick up a signal from the trackpad or keyboard on your laptop when running on power. As a result, the muscle sensor will have false readings and the Arduino's analog pin will read high.

For users using a 3.3V Arduino, we recommend adjusting the PWR jumper by cutting the default trace and adding a solder jumper between the center pad and the 3.3V side. For users using a 5V Arduino, you can leave the jumper connected to the 5V side. For more information on modifying the jumpers, check out our tutorial on working with jumper pads and PCB traces.

Stack the Arduino Shield on your chosen development board with the Arduino Uno R3 footprint.

Stacking the Arduino Shield on the Arduino Development Board with Arduino Uno R3 Footprint

Insert the TRS cable between the MyoWare 2.0 Link Shield and Arduino Shield's TRS connector. In this case, we will be using the connector labeled as A0. Make sure to adjust the code when using the other channels.

TRS Cable Between the Link Shield and Arduino

For remote applications, we recommend using a battery pack. In this case, we used AA batteries (NiMH) and a 4xAA battery pack to power the system.

Make sure to remove the power supply from your computer before connecting your Arduino with the MyoWare 2.0 Muscle Sensor to your USB port. This is to prevent noise and safeguard against electrical shock when connected to the power grid. This includes any computer docks and external monitors.

Remove Power from a Laptop that was Connected to the Main Outlet

Removing power from a laptop before connecting the MyoWare.

When ready, insert the USB cable between your Arduino and computer's USB port.

For users transmitting sensor data via Bluetooth, attach a battery pack to the RedBoard Artemis acting as the Bluetooth peripheral device. This is assuming that it has the Bluetooth peripheral example code uploaded. Connect the RedBoard Artemis acting as the Bluetooth central device to your computer's USB port. Since the Bluetooth peripheral device is disconnected, you could connect your laptop to a power supply since the MyoWare 2.0 Muscle Sensor is not connected to the main outlet. You just need to make sure to unplug the power supply every time you need to reprogram the RedBoard Artemis acting as the peripheral device.

Note: Confused about which board you are uploading code to? Try getting a sticky note and labeling each RedBoard Artemis board with the word peripheral and central.

Note: For users that are soldering, you could also solder wires to the PTH pads on the muscle sensor and connect to a microcontroller's analog input. The following image shows the MyoWare 2.0 Muscle Sensor connected to an Arduino Uno R3. However, you could connect it to the Raspberry Pi's RP2040 or any other micrcontroller that has an analog input. Just make sure to connect 3.3V for the muscle sensor's VIN if your microcontroller's system voltage is 3.3V.

MyoWare 2.0 Muscle Sensor Wired Directly to an Arduino

Image Courtesy of Advancer Technologies taken from the MyoWare 2.0 Advanced Guide

Connecting Wireless Shield to the Muscle Sensor

Note: By default, the MyoWare 2.0 Wireless Shield includes firmware to act as a peripheral device. For users simply connecting one MyoWare 2.0 Wireless Shield, you can just upload code to the central device.

Note: When uploading firmware to either the BLE peripheral or central device, make sure to install the MyoWare Arduino Library. For more information, check out the MyoWare Arduino Library.

When uploading new code to the Wireless Shield, you will need to connect a USB cable between the MyoWare 2.0 Wireless Shield and your computer's USB port. Select the POWER SOURCE on the Wireless Shield (in this case, we used the built-in LiPo battery so the switch was flipped toward the VBAT). When ready, flip the switch for the POWER to the ON position to begin uploading the modified peripheral code (i.e. MyoWareBLEPeripheral.ino) using the Arduino IDE. This is also how you would charge the built-in LiPo battery.

USB Between Wireless Shield/Muscle Sensor and Computer

After uploading code, flip the POWER switch to the OFF position. Stack the shield on top of the MyoWare 2.0 Muscle Sensor similar to the Power Shield or LED Shield. Then attach the EMG pads to the bottom of the board.

Wireless Shield, Muscle Sensor, EMG Pads

Note: You will need to stack the Wireless Shield on the MyoWare 2.0 Sensor in order to measure muscle activity. The Wireless Shield is not able to measure muscle activity by itself.

Connect a compatible ESP32 development board to your computer's USB port. This will act as a Bluetooth central device. When ready, upload the code for the Central Device (i.e. MyoWareBLECentral.ino) to the ESP32. In this case, we used the IoT RedBoard - ESP32.

At this point, your setup should look similar to the following before attaching to the Muscle Sensor to a muscle group. To keep track of what board is the peripheral and central, try labeling the boards with a Sharpie or label maker.

Setup with Peripheral and Central Labeled

Once a muscle group has been chosen, prepare the skin with alcohol wipes, remove the backs of the electrodes, and attach the stack to a muscle group. In this case, we used the forearm.

Muscle Sensor, Wireless Shield, and EMG Pads attached to the forearm

Connecting a Qwiic Enabled Device to the Wireless Shield

For users that are interested in connecting another Qwiic-enabled device, you will just need to insert a Qwiic cable between the two boards. You will just need to make an enclosure or find a way to mount the Qwiic-enabled device.

Qwiic Cable between 9DoF and Wireless Shield

External Cable

For muscles that require you to mount the sensor pads away from the sensor, snap the MyoWare 2.0 Cable Shield on the bottom of the MyoWare 2.0 Muscle Sensor. Then insert the sensor cable into the 3.5mm TRS connector.

Attach the EMG pads to the snap connectors. After cleaning the skin and selecting the muscle, peel and remove the backs of the electrodes to expose the adhesive. Then attach the pads to the target muscle group based on the MID, END, and REF.

Snap Connector	TRS Pin	Electrode Pin [CAB-12970]
Reference [REF]	Sleeve	Black
End [END]	Ring	Blue
Middle [MID]	Tip	Red

Reference Cable

Note: The built-in reference snap connector should be sufficient for most applications. However, for users having a difficult time connecting to a muscle group, we recommend getting the reference cable. This is mainly intended for large muscle groups (such as the quad, hamstring, etc.).

With a hobby knife, slice the reference jumper pad closest to the GND pin. There are traces near the jumper so you will need to make sure to avoid cutting traces that are adjacent to jumper pad. For more information on modifying the jumpers, check out our tutorial on working with jumper pads and PCB traces.

Cutting Reference Jumper Pad with Hobby Knife

Then insert the reference cable into the MyoWare 2.0 Muscle Sensor, slide the pin into the housing with the tab facing away from the board.

Reference Cable Pin Inserting into Jumper Pad

When stacking a shield on top of the MyoWare 2.0 Muscle Sensor, make sure carefully pull the cable away from the shield's snap pin.

Pull Away Reference Cable Wire While Stacking Shields on Top

Note: You'll notice that the reference cable's wire is over the MyoWare 2.0 Link Shield's reference pogo pin. The tolerance is small so you will need to make sure to pull the cable away gently when stacking a shield on top.

Pull Reference Cable Away when Stacking Link Shield

To remove the reference cable, push the tab into the housing with the end of a flathead screwdriver and gently pull the pin out of the housing.

To close the jumper pad, add a small amount of solder on the jumper pad.

Disconnecting the MyoWare Shield

When prototyping, you will want to test out different shields or you may need to adjust the trim pot. To remove the boards, you will need a flathead screwdriver. With power off, insert the flathead between the snap connectors and ensure that there are no components in the way of the flathead. Gently slide the flathead between the snap connectors.