肌电传感器 SEN0240

传感器采购自 DFRobot，基本上是即买即用。

• 购买地址

• 相关信息，这个也是。

Arduino 驱动代码：

/*
* Copyright 2017, OYMotion Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in
*    the documentation and/or other materials provided with the
*    distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
* THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
*/

#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

#include "EMGFilters.h"

#define TIMING_DEBUG 1

#define SensorInputPin A0 // input pin number

EMGFilters myFilter;
// discrete filters must works with fixed sample frequence
// our emg filter only support "SAMPLE_FREQ_500HZ" or "SAMPLE_FREQ_1000HZ"
// other sampleRate inputs will bypass all the EMG_FILTER
int sampleRate = SAMPLE_FREQ_1000HZ;
// For countries where power transmission is at 50 Hz
// For countries where power transmission is at 60 Hz, need to change to
// "NOTCH_FREQ_60HZ"
// our emg filter only support 50Hz and 60Hz input
// other inputs will bypass all the EMG_FILTER
int humFreq = NOTCH_FREQ_50HZ;

// Calibration:
// put on the sensors, and release your muscles;
// wait a few seconds, and select the max value as the threshold;
// any value under threshold will be set to zero
static int Threshold = 0;

unsigned long timeStamp;
unsigned long timeBudget;

void setup() {
    /* add setup code here */
    myFilter.init(sampleRate, humFreq, true, true, true);

    // open serial
    Serial.begin(115200);

    // setup for time cost measure
    // using micros()
    timeBudget = 1e6 / sampleRate;
    // micros will overflow and auto return to zero every 70 minutes
}

void loop() {
    /* add main program code here */
    // In order to make sure the ADC sample frequence on arduino,
    // the time cost should be measured each loop
    /*------------start here-------------------*/
    timeStamp = micros();

    int Value = analogRead(SensorInputPin);

    // filter processing
    int DataAfterFilter = myFilter.update(Value);

    int envlope = sq(DataAfterFilter);
    // any value under threshold will be set to zero
    envlope = (envlope > Threshold) ? envlope : 0;

    timeStamp = micros() - timeStamp;
    if (TIMING_DEBUG) {
        // Serial.print("Read Data: "); Serial.println(Value);
        // Serial.print("Filtered Data: ");Serial.println(DataAfterFilter);
        Serial.print("Squared Data: ");
        Serial.println(envlope);
        // Serial.print("Filters cost time: "); Serial.println(timeStamp);
        // the filter cost average around 520 us
    }

    /*------------end here---------------------*/
    // if less than timeBudget, then you still have (timeBudget - timeStamp) to
    // do your work
    delayMicroseconds(500);
    // if more than timeBudget, the sample rate need to reduce to
    // SAMPLE_FREQ_500HZ
}

驱动代码需要用到 EMGFilters 库，下载地址。

推荐每次使用时都校准一次，因为即使是同一个人，不同位置的肌电信号也是不同的。

校准流程：

• 将样例代码中的 Threshold 变量改成 0，即：static int Threshold = 0;；
• 上传样例代码至 Arduino 控制板中，然后打开 Arduino IDE 的串口监视器，观察打印的数值；
• 放松手臂上的肌肉，观察串口打印的数值。身心平静，让肌肉放松一会，观察串口监视器打印的最大数值，并记录之。如果数值太大，比如 1000 以上，可尝试微调干电极的放置位置；
• 将样例代码中的 Threshold 变量改成刚才记录的最大数值，重新上传样例代码至 Arduino 主控板。

需要注意的是：

• 使用时必须要把笔记本电脑电源断开才能出正确的波形，不然会有噪音；
• 传感器必须「紧贴」皮肤（肌肉处），否则会出现 0-40000 的规律读值。这是 Arduino 模拟输入引脚的信号。就算不接入传感器，引脚也会有读值。而驱动代码会将该读值放大。