OUTPUT DEIVCE

What is an Output Device?
Output devices in electronic systems transfer energy from the electrical energy that has been processed to another kind of energy, often light, sound or movement (kinetic). Output devices can be digital or analogue. Devices which perform an “Output” function are generally called Actuators.

SERVO MOTORS

What is a Servo Motor?
A servo motor is an electrical device which can push or rotate an object with great precision. If you want to rotate and object at some specific angles or distance, then you use servo motor. It is just made up of simple motor which run through servo mechanism. If motor is used is DC powered then it is called DC servo motor, and if it is AC powered motor then it is called AC servo motor. We can get a very high torque servo motor in a small and light weight packages. Doe to these features they are being used in many applications like toy car, RC helicopters and planes, Robotics, Machine etc.
Servo motors are rated in kg/cm (kilogram per centimeter) most hobby servo motors are rated at 3kg/cm or 6kg/cm or 12kg/cm. This kg/cm tells you how much weight your servo motor can lift at a particular distance. For example: A 6kg/cm Servo motor should be able to lift 6kg if the load is suspended 1cm away from the motors shaft, the greater the distance the lesser the weight carrying capacity.
The position of a servo motor is decided by electrical pulse and its circuitry is placed beside the motor

Image and GIF Source~ Google

Working principle of Servo Motors
A servo consists of a Motor (DC or AC), a potentiometer, gear assembly and a controlling circuit. First of all we use gear assembly to reduce RPM and to increase torque of motor. Say at initial position of servo motor shaft, the position of the potentiometer knob is such that there is no electrical signal generated at the output port of the potentiometer. Now an electrical signal is given to another input terminal of the error detector amplifier. Now difference between these two signals, one comes from potentiometer and another comes from other source, will be processed in feedback mechanism and output will be provided in term of error signal. This error signal acts as the input for motor and motor starts rotating. Now motor shaft is connected with potentiometer and as motor rotates so the potentiometer and it will generate a signal. So as the potentiometer’s angular position changes, its output feedback signal changes. After sometime the position of potentiometer reaches at a position that the output of potentiometer is same as external signal provided. At this condition, there will be no output signal from the amplifier to the motor input as there is no difference between external applied signal and the signal generated at potentiometer, and in this situation motor stops rotating.

Controlling Servo Motor: All motors have three wires coming out of them. Out of which two will be used for Supply (positive and negative) and one will be used for the signal that is to be sent from the MCU.
Servo motor is controlled by PWM (Pulse with Modulation) which is provided by the control wires. There is a minimum pulse, a maximum pulse and a repetition rate. Servo motor can turn 90 degree from either direction form its neutral position. The servo motor expects to see a pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns. For example, a 1.5ms pulse will make the motor turn to the 90° position, such as if pulse is shorter than 1.5ms shaft moves to 0° and if it is longer than 1.5ms than it will turn the servo to 180°.
Servo motor works on PWM (Pulse width modulation) principle, means its angle of rotation is controlled by the duration of applied pulse to its Control PIN. Basically servo motor is made up of DC motor which is controlled by a variable resistor (potentiometer) and some gears. High speed force of DC motor is converted into torque by Gears. We know that WORK= FORCE X DISTANCE, in DC motor Force is less and distance (speed) is high and in Servo, force is High and distance is less. Potentiometer is connected to the output shaft of the Servo, to calculate the angle and stop the DC motor on required angle.

Servo motor can be rotated from 0 to 180 degree, but it can go up to 210 degree, depending on the manufacturing. This degree of rotation can be controlled by applying the Electrical Pulse of proper width, to its Control pin. Servo checks the pulse in every 20 milliseconds. Pulse of 1 ms (1 millisecond) width can rotate servo to 0 degree, 1.5ms can rotate to 90 degree (neutral position) and 2 ms pulse can rotate it to 180 degree.
All servo motors work directly with your +5V supply rails but we have to be careful on the amount of current the motor would consumes.

https://circuitdigest.com/article/servo-motor-basics

Using Fabmods to generate tool path

Issues

Firstly I tried to iterate Neils board so it has ZLDO 1117 IC and in our Lab we had LMS117 the output volatages differ in in them as the latter is 3.3v so I decide to give it a power supply.

Major Issues
The Servo didn't work!!!
It was getting some power but the sweep code was not working, then I read the datasheet and google a bit about IO of Tiny45 and it came to know that it provide max current of 40mA and our servo required atleast 100mA.

I gave it an external supply from the power supply we had at LAB but still it didn't work. Howerver I thought that giving it the external supply will cover it's current requirement and oonly the data will be triggered using the data pin from the board I milled.
Yes I common the ground of the supply and the board which was the mistake I was doing intitailly, also I changed the servo thinking the servo I was using was wornout or something but that was agian not the case. I checked for the volage level at the output of the dat line and the vcc and gnd lines all was working fine.
After scratching a lot of head over the servo I decided to use the neopixel LED as the output device, which was going to be as the output device for my final project too.

The Code

                                

                        #include < Servo.h>

                        Servo myservo;  // create servo object to control a servo
                        // twelve servo objects can be created on most boards

                        int pos = 0;    // variable to store the servo position

                        void setup() {
                          myservo.attach(9);  // attaches the servo on pin 9 to the servo object
                        }

                        void loop() {
                          for (pos = 0; pos <= 180; pos += 1) { // goes from 0 degrees to 180 degrees
                            // in steps of 1 degree
                            myservo.write(pos);              // tell servo to go to position in variable 'pos'
                            delay(15);                       // waits 15ms for the servo to reach the position
                          }
                          for (pos = 180; pos >= 0; pos -= 1) { // goes from 180 degrees to 0 degrees
                            myservo.write(pos);              // tell servo to go to position in variable 'pos'
                            delay(15);                       // waits 15ms for the servo to reach the position
                          }
                        }
                    

                                    #include < Adafruit_NeoPixel.h>
                                                    #ifdef __AVR__
                                                     #include < avr/power.h>
                                                    #endif
                                                    #define PIN 3//data pin of led attached to the pin of the board
                                                    #define NUM_LEDS 6//Number of individual LED's
                                                    int i=0;
                                                    //create a NeoPixel strip
                                                    Adafruit_NeoPixel strip = Adafruit_NeoPixel(NUM_LEDS, PIN, NEO_GRB + NEO_KHZ800);


                                                    void setup() {
                                                      strip.begin();
                                                      strip.show();
                                                    }

                                                    void loop()
                                                    {
                                                    strip.setPixelColor(0,0,0,255);//0 led on 
                                                    strip.setPixelColor(1,255,0,0);//1st led on
                                                    strip.setPixelColor(2,0,255,0);//2nd led on  //Turning all the 6 LED's On with different color
                                                    strip.setPixelColor(3,255,0,0);//3rd led on
                                                    strip.setPixelColor(4,0,255,0);//4th led on
                                                    strip.setPixelColor(5,255,255,0);//5th led on
                                                    strip.setPixelColor(6,0,255,255);//6th led on
                                                    strip.show();
                                                    delay(1000);
                                                    for(i=0;i<6;i++)// Setting up the loop that goes till 6th led 
                                                    {
                                                      strip.setPixelColor(i,0,0,0);//The i in this is that particular numbered  LED 
                                                      strip.show();
                                                      delay(500);// a delay of 500 milliseconds
                                                    }
                                                  

                                                    }

                            

Group Work -

Visit our Lab Group page. This week our group assignment was to measure power consumption of an output device. To do so we decided to measure power of a motor.We Connected a Planetery Geared DC Motor to a Variable power supply and observed the current drawn by the motor.

Learning

• I learned about servos and it led me to read the datashit of ATtiny thoroughly to find out how much utput current does IO pin supply.
• Although I started with learning about servo but it didn't work which led me to work on the device which I'll be using for my final project so anyhow It helped to come to a step closer to my final project.
• I learned to optimize the code for the neopixel and the how to control single LED.
• I learned to debug the circuit which I've never at smd level, checking voltages at every vcc and gnd, burning simple led blink code the testing voltage across the data pin was something that will help to debug more circuits in future.
• At the end I was successfully able to use an output device with the board that I've made. I was pretty happy about it.