Flapping Halloween Vampire Bat

126

2023-10-31 | By Adafruit Industries

License: See Original Project Circuit Playground

Guide by Liz Clark

Overview

projects_upAndDown

If Halloween has snuck up on you, have no fear! This project gets you ‎from zero to flapping vampire bat with no soldering required. You'll ‎use a Circuit Playground Express, two servo motors and ‎CircuitPython to build this fun Halloween prop.

The bat's wings are mounted to two servo motors that move up and ‎down to create a flapping effect. The servo motors have alligator ‎clips that attach to the pads on the Circuit Playground Express.‎

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The NeoPixels on the Circuit Playground Express animate with a ‎swirly comet pattern.‎

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Prerequisite Guides

Adafruit Circuit Playground Express

CircuitPython LED Animations

Using Servos With CircuitPython and Arduino

Parts

This project also works with a Circuit Playground Bluefruit if the ‎Circuit Playground Express is not available.‎

Circuit Playground Bluefruit - Bluetooth Low Energy

Circuit Diagram

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Right Wing Servo

Servo GND to board GND (black wire)
Servo VIN to board 3.3V (red wire)
Servo Data to board A6 (white wire)‎

Left Wing Servo

Servo GND to board GND (black wire)
Servo VIN to board 3.3V (red wire)
Servo Data to board A3 (white wire)‎

‎3D Printing

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The Halloween bat may be assembled with 3D printed parts, ‎described below. The pieces could also be cut from other materials, ‎such as wood, acrylic or even cardboard.‎

The STL files can be downloaded directly here or from Thingiverse.‎

bat_STLfiles.zip

Thingiverse download

The Circuit Playground and servo motors mount to the body of the ‎bat. The NeoPixels are visible in the cutout for the board.‎

Each wing mounts to a servo with M2 screws.‎

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You can paint the bat's fangs and eyes to make them standout. ‎Googly Eyes work too.‎

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CircuitPython

As we continue to develop CircuitPython and create new releases, ‎we will stop supporting older releases. If you are running an older ‎version of CircuitPython, you need to update. Click the button below ‎to download the latest!‎

Install or update CircuitPython!‎

Follow this quick step-by-step for super-fast Python power :)‎

Download the latest version of CircuitPython for this board via ‎CircuitPython.org

Click the link above and download the latest UF2 file.‎

Download and save it to your Desktop (or wherever is handy.)‎

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Plug your Circuit Playground Express into your computer using a ‎known-good USB cable.‎

A lot of people end up using charge-only USB cables and it is very ‎frustrating! So, make sure you have a USB cable you know is good ‎for data sync.‎

Double-click the small Reset button in the middle of the CPX, you ‎will see all of the LEDs turn green. If they turn all red, check the USB ‎cable, try another USB port, etc.‎

‎(If double-clicking doesn't do it, try a single-click!)‎

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You will see a new disk drive appear called CPLAYBOOT. ‎

Drag the adafruit-circuitpython-etc...uf2 file onto it.‎

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The CPLAYBOOT drive will disappear, and a new disk drive will ‎appear called CIRCUITPY.‎

That's it! You're done :)

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Further Information

For more detailed info on installing CircuitPython, check ‎out Installing CircuitPython.‎

Code the Halloween Bat

Once you've finished setting up your Circuit Playground Express with ‎CircuitPython, you can access the code and necessary libraries by ‎downloading the Project Bundle.‎

To do this, click on the Download Project Bundle button in the ‎window below. It will download as a zipped folder.‎

Download Project Bundle

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# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
import board
import pwmio
import neopixel
from adafruit_motor import servo
from adafruit_led_animation.animation.comet import Comet
from adafruit_led_animation.sequence import AnimationSequence
from adafruit_led_animation.color import PURPLE

#  create 2 PWM instances for the servos
left_pwm = pwmio.PWMOut(board.A3, duty_cycle=2 ** 15, frequency=50)
right_pwm = pwmio.PWMOut(board.A6, duty_cycle=2 ** 15, frequency=50)

#  left wing servo
left_servo = servo.Servo(left_pwm)
#  right wing servo
right_servo = servo.Servo(right_pwm)

#  use onboard neopixels on CPX
pixel_pin = board.NEOPIXEL
#  number of onboard neopixels
num_pixels = 10

#  neopixels object
pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.05, auto_write=False)

#  comet animation
comet = Comet(pixels, speed=0.01, color=PURPLE, tail_length=10, bounce=True)

#  create animation sequence
animations = AnimationSequence(comet)

#  beginning angles for each wing
left_angle = 100
right_angle = 30
#  minimum range for the servos
min_range = 30
#  maximum range for the servos
max_range = 100
#  the change in degrees for the servos
degree_change = 10
#  it's not recommended to go faster than 0.05
speed = 0.05

while True:
	#  run comet animation while servos move
    animations.animate()

	#  left angle decreases by 10
    left_angle = left_angle - degree_change
	#  once it's less than 30 degrees, reset to 100
    if left_angle < min_range:
        left_angle = max_range
	#  right angle increases by 10
    right_angle = right_angle + degree_change
	#  once it's greater than 100, reset to 30
    if right_angle > max_range:
        right_angle = min_range
	#  move left wing
    left_servo.angle = left_angle
	#  move right wing
    right_servo.angle = right_angle
	#  delay
    time.sleep(0.05)

‎View on GitHub

Upload the Code and Libraries to the ‎Circuit Playground Express

After downloading the Project Bundle, plug your Circuit Playground ‎Express into the computer's USB port with a known good USB ‎data+power cable. You should see a new flash drive appear in the ‎computer's File Explorer or Finder (depending on your operating ‎system) called CIRCUITPY. Unzip the folder and copy the following ‎items to the Circuit Playground Express' CIRCUITPY drive. ‎

lib folder
code.py

Your Circuit Playground Express CIRCUITPY drive should look like ‎this after copying the lib folder and the code.py file.‎

copy_11

How the CircuitPython Code Works

The code begins by setting up two pins for the servo motors to have ‎PWM out. Then left_servo and right_servo is created as servo objects.‎

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#  create 2 PWM instances for the servos
left_pwm = pwmio.PWMOut(board.A3, duty_cycle=2 ** 15, frequency=50)
right_pwm = pwmio.PWMOut(board.A6, duty_cycle=2 ** 15, frequency=50)

#  left wing servo
left_servo = servo.Servo(left_pwm)
#  right wing servo
right_servo = servo.Servo(right_pwm)

The onboard NeoPixels are used for this project. The pin to access ‎them is board.NEOPIXEL. Then, pixels is setup as the NeoPixel object.‎

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#  use onboard neopixels on CPX
pixel_pin = board.NEOPIXEL
#  number of onboard neopixels
num_pixels = 10

#  neopixels object
pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=0.05, auto_write=False)

The Comet animation is setup and added to the AnimationSequence(). If you ‎want to change the color for the animation, you would change ‎the color property. ‎

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#  comet animation
comet = Comet(pixels, speed=0.01, color=PURPLE, tail_length=10, bounce=True)

#  create animation sequence
animations = AnimationSequence(comet)

There are a few variables for the servo motor angles that are defined ‎before the loop. You can change these values to customize the look ‎of your bat's wing flapping. ‎

min_range and max_range define the angle range of the wings. Change ‎these values if you want to increase or decrease the range of the ‎motor angles between 0 and 180. degree_change is the rate of movement ‎for the motors. If you increase this value, the motors will move more ‎abruptly; decrease the value and the motors will move more ‎incrementally. speed is the delay amount in the loop and as a result, ‎determines how fast the servo motors move.‎

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#  beginning angles for each wing
left_angle = 100
right_angle = 30
#  minimum range for the servos
min_range = 30
#  maximum range for the servos
max_range = 100
#  the change in degrees for the servos
degree_change = 10
#  it's not recommended to go faster than 0.05
speed = 0.05

In the loop, animations.animate() allows the comet NeoPixel animation to ‎run as long as the code is running.‎

‎Download File‎

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#  run comet animation while servos move
    animations.animate()

The servos move like mirror images of each other to imitate a wing ‎flapping motion. As a result, the angle of the servo on the left ‎increases while the angle of the servo on the right decreases.‎

The left_angle value decreases by the value of degree_change. Once its ‎value is less than min_range, its reset to max_range.‎

‎Download File

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#  left angle decreases by 10
    left_angle = left_angle - degree_change
	#  once it's less than 30 degrees, reset to 100
    if left_angle < min_range:
        left_angle = max_range

The right_angle value increases by the value of degree_change. Once its ‎value is greater than max_range, its reset to min_range.‎

‎Download File‎

Copy Code

#  right angle increases by 10
    right_angle = right_angle + degree_change
	#  once it's greater than 100, reset to 30
    if right_angle > max_range:
        right_angle = min_range

The servos move by changing the value of their angle property.

‎Download File

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#  move left wing
    left_servo.angle = left_angle
	#  move right wing
    right_servo.angle = right_angle
	#  delay
    time.sleep(speed)

MakeCode Version

projects_makeCodeBat

Another option for your flapping vampire bat is to code it with ‎MakeCode. You can drag and drop the .UF2 code file onto your ‎Circuit Playground Express to quickly prepare your bat to take flight.‎

Microsoft MakeCode for Adafruit is a web-based code editor that ‎provides a block editor, similar to Scratch or Code.org, and also a ‎JavaScript editor for more advanced users.‎

If you've never used the Circuit Playground Express with MakeCode ‎before, this guide is a good place to start.‎

MakeCode for Circuit Playground Express Learn Guide

Wiring

For this version, the left-wing servo data cable is attached ‎to pin A1, and the right-wing servo data cable is attached to pin A2.‎

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The Code

To download the code, click the download link at the bottom of the ‎window. To edit the code in MakeCode, click the box with arrow icon ‎in the upper right corner of the window.‎

code_13

Microsoft MakeCode | Terms of Use | Privacy | Download

You can also download the compiled .UF2 file directly below.‎

circuitplayground-cpxHalloweenBat.uf2‎

How to Upload Code

To upload code to Circuit Playground Express, follow these ‎instructions:‎

‎1) Connect your Circuit Playground Express to your computer using a ‎known, good data+power micro-USB cable and press the small reset ‎button in the center of the board. All the LEDs will flash red briefly, ‎then turn green. Your computer should now show a removable drive ‎called CPLAYBOOT. ‎

‎2) Click the Download button in the code window below to ‎download the .UF2 file to your computer.‎

‎3) Now drag and drop the .UF2 file onto the CPLAYBOOT drive in ‎your computer's file explorer or finder.‎

Once the file is dragged onto CPLAYBOOT, the drive will ‎automatically eject itself (your computer may give you a "failed to ‎eject drive correctly" error, you can ignore this). The code is now on ‎your Circuit Playground Express and ready to run!‎

Note: If you get a drive named CIRCUITPY, no worries! Press the ‎reset button twice to get a flash drive named CPLAYBOOT. The ‎project will not run if copied onto the CIRCUITPY drive as it is for ‎CircuitPython.‎

How the Code Works

When the code begins, a few variables are defined:‎

right_angle - the angle of the servo for the right wing
left_angle - the angle of the servo for the left wing
min_range - the minimum angle for the servos
max_range - the maximum angle for the servos
speed - the length of the delay
degree_change - the amount of movement for the servos

variables_14

In the loop, the NeoPixels display a rainbow animation while the ‎code is running. Then, the left_angle and right_angle values are changed ‎by the degree_change. If either value leaves the range defined ‎by min_range and max_range, then the values are reset. The servo pins set ‎the servo angles to the left_angle for the left wing and right_angle for the ‎right wing.‎

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Assembly

Wiring

Take the servo that will be mounted as the right wing and attach its ‎alligator clips to the Circuit Playground Express.‎

Servo ground (black wire) to board GND
Servo power (red wire) to board 3.3V
Servo data (white wire) to board A6/RX

wiring_16

Take the servo that will be mounted as the left wing and attach its ‎alligator clips to the Circuit Playground Express.

Servo ground (black wire) to board GND
Servo power (red wire) to board 3.3V
Servo data (white wire) to board A3‎

wiring_17

Mount the Circuit Playground Express

Mount the Circuit Playground Express with the M3 standoffs from ‎the bolt-on kit to the bat body. Utilize the following pads for ‎mounting:‎

A2‎
A1‎
A0
A7
A5
A4‎

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stand_19

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Mount the Servo Motors

Mount the servos to the bat body using M2 screws. Make sure they ‎are oriented with the circular motor gear at the top.‎

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Attach the Wings

Attach each bat wing to their respective servo gear with an M2 screw.‎

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Alternative Mounting

If you have trouble getting the M2 screw for the wings to be tight ‎enough, you can glue one of the servo horns to the wing and mount ‎them that way.‎

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Usage

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Plug the Circuit Playground Express into a USB power supply or a ‎battery pack with the JST battery port. The bat will power up and ‎you'll see its wings start flapping, along with the NeoPixel comet ‎animation.‎

There are a few parameters in the code that you can customize for ‎different effects.‎

You can adjust the angle range (min_range and max_range) of the wings ‎and the number of degrees that the wings move each time ‎‎(degree_change) for different flapping effects.‎

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You can change the color of the animation for the NeoPixels. You can ‎also change the animation that shows on the NeoPixels. Check out ‎the CircuitPython LED Animations guide to see the other options ‎available in the library.‎

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