To convert the accelerometer’s 3-axis acceleration readings into an angle value that could be interpreted as a parallel to the servo’s rotation, there was a little trig involved (taking an inverse tangent of two axes, modeled after the unit circle). The above clip is me testing the accelerometer’s analog inputs and figuring out the range of raw inputs to map to -1 and 1 for both x and y values on the unit circle.<\/p>\n
For the final transducer, I soldered part of the proto-board that the accelerometer attaches to and mounted the the board onto the servo arm via paper clips.<\/p>\n
Code<\/h3>\n\/*\r\n * 60-223, Project 1\r\n * Eric Zhao (ezhao2), Erica Fu (efu)\r\n * time spent: 20 hours \r\n *\r\n * Collaboration and sources: \r\n * 1) Eric and Erica worked together from planning, coding, to building the final project\r\n * 2) Zach assisted many times throughout the process\r\n * 3) We borrowed heavily from the Arduino guide to use the LiquidCrystal library\r\n * website link: https:\/\/www.arduino.cc\/en\/Tutorial\/LibraryExamples\/HelloWorld\r\n * 4) We implemented this moving average filter to smooth out ultrasonic data values:\r\n * https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/tutorials\/code-bites#exponential-moving-average-filter\r\n * Challenge(s): Since there are many wires, the wiring often became jumbled and confusing. \r\n * Also, the LCD display could only use certain pins, causing us to have to rewire the whole project.\r\n * The connection from the servo motor to the 3-axis-accelerometer was also quite difficult since\r\n * we had to customize parts and eventually settle for using a paperclip to make a mechanical connection.\r\n * \r\n * Next time: We will organize wiring better so that the circut is clearer so that any change \r\n * of wiring will be less confusing.\r\n *To prevent breaking any more Arduinos, Erica will double check the wiring to ensure that \r\n * there is minimal damage caused in the future.\r\n * \r\n * Description: The entire breadboard is mounted to a servo motor whose output shaft is connected to a \r\n * rigid vertical structure. Depending on the input voltage from the ultrasonic sensor, the servo motor \r\n * will output a corresponding angle, causing the entire breadboard to rotate. An accelerometer attached \r\n * to the breadboard will read the tilt angle of the breadboard caused by the servo. The input voltage \r\n * will determine the output voltage of the LED.\r\n * \r\n * Pin mapping:\r\n * \r\n * Arduino pin | type | description\r\n * ------------|--------|-------------\r\n * A0 input xInput of the 3-axis accelerometer\r\n * A1 input yInput of the 3-axis accelerometer\r\n * A2 input zInput of the 3-axis accelerometer\r\n * 9 output mini servo motor\r\n * 6 output red LED \r\n * 12 output rs pin for the LCD monitor\r\n * 11 output en pin for the LCD monitor\r\n * 5 output d4 pin for the LCD monitor\r\n * 4 output d5 pin for the LCD monitor\r\n * 3 output d6 pin for the LCD monitor\r\n * 2 output d7 pin for the LCD monitor\r\n * \r\n *\/\r\n \r\n#include <Servo.h>\r\n#include <NewPing.h>\r\n#include <LiquidCrystal.h>\r\n\r\n#define TRIGGER_PIN 8\r\n#define ECHO_PIN 7\r\n#define MAX_DISTANCE 75\r\n\r\nNewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);\r\n\r\nconst int waitTime = 250;\r\nlong prevTime = 0;\r\n\r\nconst int xInput = A0;\r\nconst int yInput = A1;\r\nconst int zInput = A2;\r\nconst int SERVOPIN = 9;\r\nconst int LED = 6;\r\nServo SERVO;\r\n\r\nfloat filtered_val = 0; \/\/ this variable, of type float (decimal), holds the filtered sensor value\r\nconst float PREV_WEIGHT = 0.8; \/\/ this variable, of type float (decimal), determines the previously filtered value's weight.\r\nconst float CUR_WEIGHT = 1 - PREV_WEIGHT; \/\/ this variable, of type float (decimal), determines the current sample's weight.\r\nconst int SENSOR_PIN = A0; \/\/ this variable, of type int, determines the sensor's pin.\r\n\r\n\/\/ initialize the library by associating any needed LCD interface pin\r\n\/\/ with the arduino pin number it is connected to\r\nconst int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;\r\nLiquidCrystal lcd(rs, en, d4, d5, d6, d7);\r\n\r\nvoid setup() {\r\n \/\/ put your setup code here, to run once:\r\n pinMode(xInput, INPUT);\r\n pinMode(yInput, INPUT);\r\n pinMode(zInput, INPUT);\r\n pinMode(LED, OUTPUT);\r\n SERVO.attach(SERVOPIN);\r\n Serial.begin(115200);\r\n\r\n \/\/ set up the LCD's number of columns and rows:\r\n lcd.begin(16, 2);\r\n}\r\n\r\nvoid loop() {\r\n \/\/ put your main code here, to run repeatedly:\r\n \r\n delay(50);\r\n \/\/raw data by axis from accelerometer\r\n int x = analogRead(xInput);\r\n int y = analogRead(yInput);\r\n int z = analogRead(zInput);\r\n \/\/data from accelerometer, mapped to units -1000 to 1000\r\n int xVect = map(x, 260, 390, -1000, 1000);\r\n int yVect = map(y, 250, 380, -1000, 1000);\r\n int zVect = map(z, 320, 385, 0, 1000);\r\n \/\/below variables are the above vars but divided by 1000 to achieve unit circle\r\n float xVectUnbound = xVect\/1000.0; \r\n float yVectUnbound = yVect\/1000.0;\r\n float zVectUnbound = zVect\/1000.0;\r\n \/\/constraining final readings to unit circle -1 to 1\r\n float xVectFinal = constrain(xVectUnbound, -1, 1); \r\n float yVectFinal = constrain(yVectUnbound, -1, 1);\r\n float zVectFinal = constrain(zVectUnbound, 0, 1);\r\n \/\/final arctan value (takes two axes and converts into degrees)\r\n float degreeVal = atan2(xVectFinal, zVectFinal) * 180\/PI;\r\n\r\n \/\/creates a weighted reading\r\n float cur_reading = sonar.ping_cm();\r\n if(cur_reading != 0){\r\n filtered_val = filtered_val * PREV_WEIGHT + cur_reading * CUR_WEIGHT;\r\n }\r\n\r\n \/\/takes a smoothed out sonar reading and converts to servo degrees\r\n int servoVal = map(filtered_val, 0, 75, 0, 180);\r\n \/\/takes accelerometer degree reading and converts to\r\n int outputVal = map(degreeVal, -55, 90, 0, 255);\r\n if(cur_reading != 0 && servoVal > 0){\r\n SERVO.write(servoVal);\r\n }\r\n \r\n if(outputVal > 0){\r\n analogWrite(LED, outputVal);\r\n }\r\n\r\n int inputDisplay = map(filtered_val, 0, 75, 0, 100);\r\n int middleActDisplay = map(servoVal, 0, 180, 0, 100);\r\n int middleSensorDisplay = map(outputVal, 0, 255, 0, 100);\r\n\r\n if(millis() - prevTime > waitTime){\r\n \/\/outputs data to LCD display 4 times a second\r\n lcd.setCursor(0,0);\r\n lcd.print((String)\"i:\"+ inputDisplay);\r\n lcd.setCursor(5,0);\r\n lcd.print((String)\"m:\" + middleActDisplay);\r\n lcd.setCursor(7,1);\r\n lcd.print(middleSensorDisplay);\r\n lcd.setCursor(11,1);\r\n lcd.print((String)\"o:\" + middleSensorDisplay);\r\n\r\n prevTime = millis();\r\n }\r\n\r\n}<\/pre>\n <\/p>\n
Reflection<\/h3>\n
We found a lot more issues throughout the span of this project than either of us imagined would happen! Different libraries conflicted with each other (for example, the Servo library shut down certain pins that the NewPing ultrasonic library utilized). Mechanical connections between certain parts were difficult to make robust enough to handle the servo\u2019s torque; we ended up using paperclips for a lot of these as compared to tape, which was a lot weaker.<\/p>\n","protected":false},"excerpt":{"rendered":"
Initial Sketches and Block Diagram: For the middle step on our transducer, we were deciding between having a servo drive a potentiometer, having a servo drive a platform…<\/p>\n","protected":false},"author":175,"featured_media":12360,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[86],"tags":[],"_links":{"self":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/12348"}],"collection":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/users\/175"}],"replies":[{"embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/comments?post=12348"}],"version-history":[{"count":15,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/12348\/revisions"}],"predecessor-version":[{"id":12691,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/posts\/12348\/revisions\/12691"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/media\/12360"}],"wp:attachment":[{"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/media?parent=12348"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/categories?post=12348"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/courses.ideate.cmu.edu\/60-223\/s2021\/work\/wp-json\/wp\/v2\/tags?post=12348"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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