Published November 1, 2016 © GPL3+

Blynky Halloween Candy Hand

This project uses Blynk (Esp8266), a 3-D printed hand, and two servos to make a remote controlled Halloween hand gag.

IntermediateFull instructions provided4 hours1,041

Things used in this project

Hardware components

SparkFun Blynk Board - ESP8266

Apple iPhone

I had an iPhone, but any android device would be fine too.

Servos (Tower Pro MG996R)

I used two MG996R Metal Gears Digital RC Servo Motors

4xAA battery holder

Software apps and online services

Blynk

Arduino IDE

Hand tools and fabrication machines

3D Printer (generic)

Story

Introduction

For the past few years, for Halloween decorations, I have been setting up the Pumpkin Head Bluegrass Band. It has four members:

Daddy pumpkin on Banjo

Momma pumpkin on washtub Bass

Little kid on the Fiddle

Big kid on the Jug

Pumpkin Head Bluegrass Band

This year I decided to add a remote controlled robotic hand as a gimmick for handing out candy. I recently attended a Hackster.io Digital Design Workshop by Tom Moxon and Stephen Borsay for an Introduction to Blynk, and I decided to use the Blynk as the controller for the hand.

Three Modes

The hand has three modes:

Open hand

Come here and take this candy if you dare.

Grab

Here's a video of it in action:

Wouldn't you like this nice piece of candy?

It worked pretty well. Some of the little kids were kind of confused as to what to do, but most of them got a kick out of it. One of the fingers started to bind up a bit, so I tried a quick field repair and bent the middle finger back. But this only made matters worse because it made it look like the pumpkin kid was flippin the bird at anyone trying to take the candy. But the problem eventually worked itself out and began operating correctly again.

Electronics

The electronics are pretty simple. I used an Sparkfun Blynk board, but a Sparkfun Thing or any Esp8266 board should work. The four batteries supply 6 volts to the servos. The processor board gets it's own power from the USB connector and the ground connections of the two supplies are tied together. Other than that, the only other required connection is between GPIO15 to the servo control line and from GPIO16 to the other servo.

Arduino Software

There are three character array which need to be set to:

Network SSID.

Network password.

Blynk Auth Token. This string is created when an new Blynk smartphone app is made.

The C code uses the ESP8266 servo library to control the servos. The loop() function calls the required Blynk.run() function and also wiggles the index finger every 1/2 second if it is in the "come" mode. I also have it blinking the blue LED every three seconds. That is optional, but is an easy way to see if the code is running.

There are three required BLYNK_WRITE() functions. These are virtual pin handlers used to detect if the user clicked any of the buttons on the smart phone Blynk app. The functions set the servos positions. The "V2" virtual pin handler also sets up the conditions for the index finger wiggling to occur at 1/2 second intervals. I also added an additional BLYNK_WRITE function for virtual pin V4. This function responds to slider control movements. The slider can send values from 0 to 180 which sets both servos to the specified angle.

Candy Hand Blynk App

I used an iPhone but any current IOS or Android device should work also. Blynk apps are pretty simple. I just add three button controls (and a slider control).

Then configure them to control the virtual pins.

3D Printed Parts and assembly

I used the Raptor Reloaded Hand that can be found on Thingiverse. I also made two 3D printed mounts to hold the MG996R RC Servos. I replaced the wrist portion of the hand with a piece of wood and screwed my servo mounts onto the board.

One servo controls the index finger and the other servos controls the other fingers. I used the long, two sided servo arms. Each finger has two strings connected to it for a total of 10 strings. Pulling one string causes a finger to extend and pulling the other will retract it. On the index finger, the two strings go to opposite sides of the servo, so moving the servo to 0 degrees extends the finger and 180 retracts it. For the other fingers, all of the retracting control strings were tied together to one side of the servo and the other strings were connected to the other side of the servo.

Wrapping it up

The final step was to hook up the servos to the Blynk board, connect up the batteries, attach the hand to my pumpkin band member, put a snickers bar in the palm and wait for the kids to arrive.

I put a latex glove over the hand to make it look more real, but next year I think I'll just stick with the 3D printed look. I'm also thinking about adding an HC-SR04 distance sensor and making "come here" and "grab" modes fully automated.

Schematics

Code

Blynky Candy Hand

#include <Servo.h>


// arduino setup: Generic esp8266; DIO; 40MHz; 80Mhz; 1M(128K); 115200

/**************************************************************
 * 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
 *   Blynk community:            http://community.blynk.cc
 *   Social networks:            http://www.fb.com/blynkapp
 *                               http://twitter.com/blynk_app
 *
 * Blynk library is licensed under MIT license
 * This example code is in public domain.
 *
 **************************************************************
 * This example runs directly on ESP8266 chip.
 *
 * You need to install this for ESP8266 development:
 *   https://github.com/esp8266/Arduino
 *
 * Please be sure to select the right ESP8266 module
 * in the Tools -> Board menu!
 *
 * Change WiFi ssid, pass, and Blynk auth token to run :)
 *
 **************************************************************/

#define BLYNK_PRINT Serial    // Comment this out to disable prints and save space
#include <ESP8266WiFi.h>
#include <BlynkSimpleEsp8266.h>

// **** Embedis ***  Embedded Dictionary Server

// You should get Auth Token in the Blynk App.
// Go to the Project Settings (nut icon).
char auth[] = "YOU NEED TO ADD YOUR BLYNK AUTH TOKEN"//;

// Your WiFi credentials.
// Set password to "" for open networks.
char ssid[] = "YOU NEED TO ADD YOUR NETWORK SSID"//;
char pass[] = "YOU NEED TO ADD YOUR NETWORK PASSWORD"//;

Servo indexFinger;
Servo otherFingers;

bool comeHere = false;
bool comeClosed = false;
unsigned long cometime = 0;
unsigned long lasttime = 0;



void setup()
{
  indexFinger.attach(16);  // attaches the servo on GIO to the servo object 
  otherFingers.attach(15);  // attaches the servo on GIO to the servo object 

  Serial.begin(115200);
  Blynk.begin(auth, ssid, pass);
  pinMode(5, OUTPUT);  // blue light on the Blynk to show it's alive
}

void loop()
{
  Blynk.run();
  unsigned long time = millis();

  if (comeHere && (time > (cometime+500)))
  {
    // in come here mode, move index finger at a 1/2 sec rate.
    cometime = time;
    indexFinger.write(comeClosed ? 0 : 180);
    comeClosed = !comeClosed;
  }

  if (time > lasttime+3000)
  {
    // blink the blue led every 3 seconds.
    digitalWrite(5, !digitalRead(5)); 
    lasttime = time;  
  }
}

BLYNK_WRITE(V1)
{
  // open hand
  indexFinger.write(0);
  otherFingers.write(0);
  comeHere = false;
}

BLYNK_WRITE(V2)
{
  // start the index finger moving
  unsigned long time = millis();
  cometime = time;  

  indexFinger.write(180);
  otherFingers.write(0);
  comeHere = true;
  comeClosed = true;
}

BLYNK_WRITE(V3)
{
  // close hand
  indexFinger.write(180);
  otherFingers.write(180);
  comeHere = false;
}

BLYNK_WRITE(V4)
{
  // This controls all fingers with a slider control
  int directPos = param.asInt();
  indexFinger.write(directPos);
  otherFingers.write(directPos);
  comeHere = false;
}

Credits

Alan Zimmerman

2 projects • 0 followers

Blynky Halloween Candy Hand

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Three Modes

Electronics

Arduino Software

Candy Hand Blynk App

3D Printed Parts and assembly

Wrapping it up

Custom parts and enclosures

Servo Bracket

Raptor Reloaded Hand

Schematics

Simple schematic

3_p1XxH1TsXR.jpg

Code

Blynky Candy Hand

Credits

Alan Zimmerman

Comments

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Blynky Halloween Candy Hand

Blynky Halloween Candy Hand

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Three Modes

Electronics

Arduino Software

Candy Hand Blynk App

3D Printed Parts and assembly

Wrapping it up

Custom parts and enclosures

Servo Bracket

Raptor Reloaded Hand

Schematics

Simple schematic

3_p1XxH1TsXR.jpg

Code

Blynky Candy Hand

Credits

Alan Zimmerman

Comments

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