Ever wondered how it would be to make a quadrupedal spider walk. This a cool way to learn about Inverse dynamics of robotic system, Use of Polar co-ordinates in Robots, How robots move and what are possible gaits? For this project we will be using Crawl Gait (you can read more about this here https://cjme.springeropen.com/articles/10.1186/s1... ). I have used following blogs for making this robot: https://makezine.com/2016/11/22/robot-quadruped-a...https://create.arduino.cc/projecthub/diyguyChris/a...

For making this project I have used following items:

NodeMcu (esp8266) [I have used this specific NodeMcu for this project (https://www.amazon.in/gp/product/B00UY8C3N0/ref=pp...)

I have used this specific model as a structure for this robot (https://www.amazon.in/gp/product/B00UY8C3N0/ref=pp...)
Some batteries (this model has slot for AA batteries so better you buy that)
8 Hobby Servo motors (I have used SG90 but you can also use MG90)
Many jumper wires (All kinds)
Breadboard
LM7805
Several Capacitors and resistors

The last 6 items are for making 5v voltage regulator that is best suited for NodeMcu and Servo motors. One of the reason i made 5v voltage regulator is because 8 servo motor requires a lot of power and NodeMcu will not be enough for powering all this servo motors.

You can follow this link for making 5v power regulators: ( https://www.ti.com/lit/ds/symlink/lm340.pdf ), ( http://www.learningaboutelectronics.com/Articles/... )

Step 1: Assemble the Physical Model

In my case i followed the instruction in the manual and all the components were given in the booklet itself. However, you can find a similar model on the internet and 3D print it or get an acrylic cut according to the model. Do not forget to properly add the motors at right places.

Step 2: Make the Electronic Circuit

Connect the wires from Servo motors to nodeMcu and voltage regulator. The power wires should be connected to voltage regulator and logic wires to NodeMcu.

Step 3: The Hard Part (coding)

Here comes the code:

/*************************************************************
Download latest Blynk library here: https://github.com/blynkkk/blynk-library/releases/latest

Blynk is a platform with iOS and Android apps to control Arduino, Raspberry Pi and the likes over the Internet. You can easily build graphic interfaces for all your projects by simply dragging and dropping widgets.

Downloads, docs, tutorials: http://www.blynk.cc Sketch generator: http://examples.blynk.cc Blynk community: http://community.blynk.cc Follow us: https://www.fb.com/blynkapp http://twitter.com/blynk_app

Blynk library is licensed under MIT license This example code is in public domain.

*************************************************************

This sketch shows how to read values from Virtual Pins

App project setup: Slider widget (0...100) on Virtual Pin V1 *************************************************************

* Comment this out to disable prints and save space */ #define BLYNK_PRINT Serial

#include #include #include

// You should get Auth Token in the Blynk App. // Go to the Project Settings (nut icon). char auth[] = "add_you_own";

// Your WiFi credentials. // Set password to "" for open networks. char ssid[] = "meena"; char pass[] = "12345678";

Servo liga[4][2]; const int liga_pin[4][2]={ { 5, 4 }, { 2, 0 }, { 14,12 }, { 13, 15 } } ;

const int qspeed=10;

const int ipo=110;

const int var=40;

// This function will be called every time Slider Widget // in Blynk app writes values to the Virtual Pin V1 BLYNK_WRITE(V0) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { forward(); } }

BLYNK_WRITE(V1) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { backward(); } }

BLYNK_WRITE(V2) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { left(); } }

BLYNK_WRITE(V3) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { right(); } }

BLYNK_WRITE(V4) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { rotate_right(); } }

BLYNK_WRITE(V5) { int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable

if(pinValue==1)// process received value { rotate_left(); } }

void setup() { // Debug console Serial.begin(9600);

Blynk.begin(auth, ssid, pass); // You can also specify server: //Blynk.begin(auth, ssid, pass, "blynk-cloud.com", 80); //Blynk.begin(auth, ssid, pass, IPAddress(192,168,1,100), 8080);

servo_attach();

}

void loop() { Blynk.run(); }

void servo_attach(void) { liga[0][0].attach(5); liga[0][1].attach(4); liga[1][0].attach(2); liga[1][1].attach(0); liga[2][0].attach(14); liga[2][1].attach(12); liga[3][0].attach(13); liga[3][1].attach(15); }

//_______________________________________________________________

void polar_to_servo(int leg,int angle) { if(leg == 0) { angle=angle-30; }

int x=liga[leg][0].read(); liga[leg][1].write(160); delay(100); if(x < angle) { for(int i=x;i<=angle;i +=qspeed) { liga[leg][0].write(i); delay(15); } }

if(x > angle) { for(int i=x;i>=angle;i -=qspeed) { liga[leg][0].write(i); delay(15); } }

if(leg == 0) { liga[leg][1].write(10); } liga[leg][1].write(20); delay(100); }

//_______________________________________________________________

void drag(int leg,int angle) {

if(leg == 0) { angle=angle-30; }

int x=liga[leg][0].read(); if(x

else if(x>angle) { for(int i=x;i>=angle;i -=qspeed) { liga[leg][0].write(i); } } }

//_______________________________________________________________

void forward() { //Step 1 polar_to_servo(0,ipo); // 0th position -->30 polar_to_servo(1,ipo+var); // 0th position -->60 polar_to_servo(2,ipo-var); // 0th position -->60 polar_to_servo(3,ipo); // 0th position -->60 //step2 polar_to_servo(1,ipo-var);

//step3 drag(0,ipo-var); drag(1,ipo); drag(2,ipo); drag(3,ipo-var); delay(300);

//step4 polar_to_servo(3,ipo+var);

//step5 polar_to_servo(0,ipo+var);

//step6 drag(0,ipo); drag(1,ipo+var); drag(2,ipo+var); drag(3,ipo); delay(300);

//step7 polar_to_servo(2,ipo-var); }

//_______________________________________________________________

void backward() {

//Step 1 polar_to_servo(2,ipo); // 0th position -->30 polar_to_servo(3,ipo+var); // 0th position -->60 polar_to_servo(0,ipo-var); // 0th position -->60 polar_to_servo(1,ipo); // 0th position -->60 //step2 polar_to_servo(3,ipo-var);

//step3 drag(2,ipo-var); drag(3,ipo); drag(0,ipo); drag(1,ipo-var); delay(300);

//step4 polar_to_servo(1,ipo+var);

//step5 polar_to_servo(2,ipo+var);

//step6 drag(2,ipo); drag(3,ipo+var); drag(0,ipo+var); drag(1,ipo); delay(300);

//step7 polar_to_servo(0,ipo-var);

}

//_______________________________________________________________

void right() { //Step 1 polar_to_servo(1,ipo); // 0th position -->30 polar_to_servo(2,ipo+var); // 0th position -->60 polar_to_servo(3,ipo-var); // 0th position -->60 polar_to_servo(0,ipo); // 0th position -->60 //step2 polar_to_servo(2,ipo-var);

//step3 drag(1,ipo-var); drag(2,ipo); drag(3,ipo); drag(0,ipo-var); delay(300);

//step4 polar_to_servo(0,ipo+var);

//step5 polar_to_servo(1,ipo+var);

//step6 drag(1,ipo); drag(2,ipo+var); drag(3,ipo+var); drag(0,ipo); delay(300);

//step7 polar_to_servo(3,ipo-var); }

//_______________________________________________________________

void left() { //Step 1 polar_to_servo(3,ipo); // 0th position -->30 polar_to_servo(0,ipo+var); // 0th position -->60 polar_to_servo(1,ipo-var); // 0th position -->60 polar_to_servo(2,ipo); // 0th position -->60 //step2 polar_to_servo(0,ipo-var);

//step3 drag(3,ipo-var); drag(0,ipo); drag(1,ipo); drag(2,ipo-var); delay(300);

//step4 polar_to_servo(2,ipo+var);

//step5 polar_to_servo(3,ipo+var);

//step6 drag(3,ipo); drag(0,ipo+var); drag(1,ipo+var); drag(2,ipo); delay(300);

//step7 polar_to_servo(1,ipo-var); }

void rotate_right() { //Step 1 polar_to_servo(0,ipo); // 0th position -->30 polar_to_servo(1,ipo+var); // 0th position -->60 polar_to_servo(2,ipo-var); // 0th position -->60 polar_to_servo(3,ipo); // 0th position -->60 //step2 polar_to_servo(1,ipo-var);

//step3 drag(0,ipo+var); drag(1,ipo-var); drag(2,ipo); drag(3,ipo+var); delay(300);

//step4 polar_to_servo(0,ipo-var);

//step5 polar_to_servo(1,ipo-var);

polar_to_servo(3,ipo-var);

//step6 drag(0,ipo); drag(1,ipo+var); drag(2,ipo+var); drag(3,ipo); delay(300);

//step7 polar_to_servo(2,ipo-var); polar_to_servo(3,ipo+var); }

void rotate_left() { //Step 1 polar_to_servo(1,ipo); // 0th position -->30 polar_to_servo(2,ipo+var); // 0th position -->60 polar_to_servo(3,ipo-var); // 0th position -->60 polar_to_servo(0,ipo); // 0th position -->60 //step2 polar_to_servo(2,ipo-var);

//step3 drag(1,ipo+var); drag(2,ipo-var); drag(3,ipo); drag(0,ipo+var); delay(300);

//step4 polar_to_servo(1,ipo-var);

//step5 polar_to_servo(2,ipo-var);

polar_to_servo(0,ipo-var);

//step6 drag(1,ipo); drag(2,ipo+var); drag(3,ipo+var); drag(0,ipo); delay(300);

//step7 polar_to_servo(3,ipo-var); polar_to_servo(0,ipo+var); }

Step 4: Further Explanation

I have used Blynk app for controlling the robot through wifi. That is the best part of NodeMcu that it can be used as standalone device without any other additional device.