“hump” is due to activity in the ventricles of the heart.
Given that my heart rate was a little over 60 beats/minute
during the session, the FFT (shown in Photo 7) shows a
peak in energy at around 60 Hz. Again, each of the smaller
blocks in the grid is 50 Hz.
Taking It from Here
This platform is ripe for extension and experimentation.
The most obvious include:
• Adding more dynamic user feedback, such as a bar
LED or OLED screen display coupled to a force sensor on
the gripper instead of the simple switch and single LED.
• Adding EMG sensors to control other servos in a
chain, such as a complete robot arm.
• Using the ECG (heart) rate to control a gripper or
• Building a biofeedback device to develop focused
recruitment, as a physical training aid.
• Building a game in which users — each with EMG
I’ve been working on controlling a multi-axis robot arm
with EMG. The simplest direct approach is to use a separate
sensor on each of several muscles, providing independent
control of the robot arm. However, I found the lack of
A better approach — at least based on my
experimentation — is to buffer the signals with the Arduino
and fire a few rules before activating a servo. For example,
if the base is already extended, you might want to limit the
extension of the robot elbow joint, thereby avoiding
stripping the gears in the base servo.
For more information on how to best use electrical
signals generated by the body, search online for “EEG,”
“EMG,” and “EKG.” If you want to step up to more
powerful hardware, consider the boards available from
openBCI.com. Their EEG monitoring hardware is especially
attractive, given the price and functionality. SV
SERVO 04.2017 45
Photo 7. FFT of cardiac activity, with a
pronounced peak at 60 Hz.
Photo 6. ECG signal with the sensor placed
over the heart.
Introducing the ME Labs D-Stick!
PICBASIC PRO is a trademark of Microchip Technology Inc. in the USA and other countries.
PIC is a registered trademark of Microchip Technology Inc. in the USA and other countries. Available now at melabs.com contact us at email@example.com
The ME Labs Standard D-Stick provides all the functionality of Microchip’s 40-pin PIC16F1937 in a hardware module
that includes a USB on-board programmer and virtual COM port. The D-Stick is a compact, simple and easy to use
alternative to connecting a serial port, programmer, power supply, etc. to a solderless breadboard for project
development. After development, simply replace the D-Stick with the pinout-compatible PIC16F1937 for volume
- Pinout is identical to Microchip’s standard 40-pin DIP
- Round, machined pins are easy on spring contacts allowing for multiple insertion cycles
- Built-in micro-USB port supplies power, a programming connection and a virtual com port
- Suitable for serial in-circuit debugging
- Compatible with all ME Labs Trainer programs
- Standard version – based on PIC16F1937 compatible with the FREE PBP Student Edition
- Advanced Version – based on PIC18F compatible with PBP Gold Edition (Sold Separately)