Video

Introduction to BSL PRO H40 EMG-Controlled Robotic Arm Lesson Set of 10 labs to build a functional robotic arm grip using EMG signal input.

In BSL PRO H40 Lab 1, students perform a basic breadboard setup that is required for all labs and build a square wave oscillator. A square wave oscillator is a common tool used for testing electronics and it will be used to test the circuits that are built in Labs 2-9. In this lab students also learn about mathematical principles that are used throughout the lesson, such as Fast Fourier Transform or FFT.

BSL PRO H40 EMG-Controlled Robotic Arm Lab 2 is the Instrumentation Amplifier lab. In this lab, students build two identical instrumentation amplifiers for both channels of EMG that will ultimately control the simplified robotic arm. To assess the InAmps circuitry, differential gain, common-mode gain and offset are determined. Students also calculate the common mode rejection ratio to evaluate the InAmp’s ability to reject noise. Sample data for differential gain, offset and common mode gain are displayed.

In BSL PRO H40 EMG-Controlled Robotci Arm Lab 3, students construct two identical 10 Hz High Pass Filters. Each filter is tested using the square wave generator built in Lab 1 to assess the high pass filter response. In the data report, students compare the estimated response against their actual results and reason the differences. Concepts such as the Sallen-Key filter configuration, DC offsets, and cut-off frequencies are also covered in this lab. For data analysis, students also use the 1 interval difference algorithm and FFT.

In Lab 4 of the H40 EMG-Controlled Robotic Arm Lesson Set, students construct two positive gain block amplifiers. The function of the positive gain block is to further amplify the AC portion of the EMG signal by 10. Students also investigate the importance behind the order of circuits in this lab since the gain block is strategically placed after the InAmp and 10 Hz High Pass Filter to only amplify signals with frequencies above 10 Hz. For verification, students calculate the amplifiers differential gain.

Students follow BSL PRO H40 Lab 5 to create two low pass filters at 500 Hz. The purpose of the low pass filter is to limit the response of the system to only the frequencies of interest. The 500 Hz limit is set since un-filtered EMG signals typically reside around 0.5 to 5 mV. In this lab students also learn about filter types that are very important for physiological recordings, such as Butterworth and Bessel filters. Students learn about different filter characteristics and also compare how filter responses can vary in magnitude, phase, and delay. In the data report, the low pass filter is evaluated using the 1 interval difference and FFT as shown in this video. Eventually, students select data from 0-500 Hz and measure Delta to verify the 3 db cutoff. Measurements are then added to the data report.

In BSL PRO H40 EMG-Controlled Robotic Arm Lab 6, students construct two 60 or 50 Hz notch filters, depending on their country of origin. This lab is critical for signal processing since a typical workspace contains many wall-mounted mains power outlets which can flood the signal with 50 or 60 Hz noise. The presence of motors and efficient lighting (fluorescent or LED) also contributes to noise onto the mains power distribution. Individually, these contributing factors may be small, however, when considered collectively, they can have a substantial effect on your signal output. To examine whether the notch filter attenuates 50 or 60 Hz noise, students use the 1 interval difference and FFT.

In BSL PRO H40 EMG-Controlled Robotic Arm Lab 7, students construct two adjustable gain blocks for fine-tuning the gain of the EMG-controlled robotic arm. The gain can be changed by using a screwdriver to turn the potentiometer clockwise or counterclockwise to increase or decrease the gain. The potentiometer allows for a variable gain range between 1 and 51 which students record and verify.

In BSL PRO H40 EMG-Controlled Robotic Arm Lab 8, students construct two absolute value circuits to ensure that the output signal is never less than zero. This is important since, by nature, EMG yields positive and negative signal values. To assess the absolute value circuit, peak to peak and mean measurements are taken and evaluated in the data report.

In BSL PRO EMG-Controlled Robotic Arm Lab 9, students build the 2nd low pass filter in the circuit. The 2nd low pass filter is necessary to provide a usable signal for controlling the robotic arm. Since the 1 Hz low pass filter has a slow response time, in this lab students use the slope method to determine the frequency response of the filters. Students then compare if their actual results match the calculated frequency response.