Matrix Portal Money-Sensing Tip Jar

By Adafruit Industries

Courtesy of Adafruit

Guide by Erin St Blaine

Overview

Say "Thank You" in a fun and interactive way with this money-sensing tip jar. Whenever someone drops in a tip, the LED matrix at the back of the jar will reward them with a fun animation and some heartfelt gratitude.

 

This is a fairly easy build, using an upcycled snack jar to collect your bountiful tips and powered by a Matrix Portal M4 board plugged into the RGB matrix of your choice. Use our premade images or upload your own animations to make a custom "thank you" message for your most generous customers.

Jar_1

Difficulty Level

This is a beginner project that doesn't require any soldering - you just need a screwdriver, some cutting tools, and some strong tape. I've also included an option that uses soldered headers for a slightly more secure build.

Materials Needed

Choose the RGB Matrix size that best fits your jar. You can see all the different sizes here. I used the 4mm pitch 64x32 size.

You'll also need a Time of Flight sensor. This is a very cool little sensor that uses a laser to detect proximity and works within a really tiny range of a few millimeters.

Be sure to get one of the suggested cables to attach it to your Matrix Portal as well. Check out the "Add the Sensor" page for more details.

Or:

Tools Needed

  • Goo-gone or other solvent to remove any labels
  • Box knife, rotary tool or saw to cut the plastic jar
  • Rotary tool or heat tool to cut the lid
  • Soldering iron if you're using the header-attachment method for the sensor (not needed if you're using the STEMMA plug-in cable)
  • Gaffer's tape or other strong tape
  • LED diffusion panel (optional)

Prep the MatrixPortal

Power Prep

The MatrixPortal supplies power to the LED matrix display panel via two standoffs. These come with protective tape applied (part of the Adafruit manufacturing process) which MUST BE REMOVED!

Use some tweezers or a fingernail to remove the two amber circles.

prep_2

prep_3

Power Terminals

Next, screw in the spade connectors to the corresponding standoff.

  • red wire goes to +5V
  • black wire goes to GND

spade_4

spade_5

Panel Power

Plug either one of the four-conductor power plugs into the power connector pins on the panel. The plug can only go in one way, and that way is marked on the board silkscreen.

panel_6

panel_7

Board Connection

Now, plug the board into the left side shrouded 8x2 connector as shown. The orientation matters, so take a moment to confirm that the white indicator arrow on the matrix panel is oriented pointing up and right as seen here and the MatrixPortal overhangs the edge of the panel when connected. This allows you to use the edge buttons from the front side.

Check nothing is impeding the board from plugging in firmly. If there's a plastic nub on the matrix that's keeping the Portal from sitting flat, cut it off with diagonal cutters.

board_7b

board_7a

Portal_8

Portal_9

For info on adding LED diffusion acrylic, see the page LED Matrix Diffuser.

Add the Sensor

Easy Plug and Play with Stemma QT

The simplest way to attach the sensor is to use this STEMMA cable. No soldering required! Just plug it right in to the port on either side.

cable_10

Soldering Non-QT Boards

I didn't have a double-ended STEMMA cable on hand during the build, so I used a slightly different method using this STEMMA-to-male-header pin cable. The benefit of this was that the female header on the sensor creates a really stable way to attach the sensor in a perpendicular orientation by the money slit.

cable_11

Solder your female header onto the bottom side of the sensor. Plug in the four cables into the first four header ports as shown: red to VIN, black to G, yellow to SCL, and blue to SDA.

If you're new to headers, you can check out this guide for some tips.

Plug the other end into your MatrixPortal and you're ready to go.

solder_12

solder_13

Install CircuitPython

CircuitPython is a derivative of MicroPython designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY drive to iterate.

Set up CircuitPython Quick Start!

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

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

Further Information

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

Click the link above and download the latest UF2 file.

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

file_14

Plug your MatrixPortal M4 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 Reset button (indicated by the green arrow) on your board, and you will see the NeoPixel RGB LED (indicated by the magenta arrow) turn green. If it turns red, check the USB cable, try another USB port, etc.

If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right!

portal_15

You will see a new disk drive appear called MATRIXBOOT.

Drag the adafruit_circuitpython_etc.uf2 file to MATRIXBOOT.

disk_17

disk_16

The LED will flash. Then, the MATRIXBOOT drive will disappear and a new disk drive called CIRCUITPY will appear.

That's it, you're done! :)

drive_18

Code with CircuitPython

This sample code will display .bmp image that encourages folks to leave you a tip. Whenever someone drops a coin or a bill through the slot, a "Thank You" animation with fireworks will play.

You can create and upload your own images, and also customize the number of times the animation plays before resetting.

Libraries

We'll need to make sure we have these libraries installed. (Check out this link on installing libraries if needed.)

  • adafruit_bus_device
  • adafruit_debouncer
  • adafruit_lis3dh
  • adafruit_matrixportal
  • adafruit_slideshow
  • adafruit_vl6180x

libraries_19

Text Editor

Adafruit recommends using the Mu editor for editing your CircuitPython code. You can get more info in this guide.

Alternatively, you can use any text editor that saves simple text files.

Code

Click the Download: Project Zip File link below in the code window to get a zip file with all the files needed for the project. Copy code.py from the zip file and place on the CIRCUITPY drive.

You'll also need to copy the following files to the CIRCUITPY drive. See the graphic at the top of the page as to filenames and where they go):

  • /bmps directory, which contains the graphics .bmp files.

The button below contains our sample graphics: a "Feeling Tipsy?" .bmp file, and a "Thank You" fireworks animation sprite sheet.

bmps.zip

Download: Project Zip or code.py | View on Github

Copy Code
"""
Motion-sensing Animation Example using the Matrix Portal and 64 x 32 LED matrix display
Written by Melissa LeBlanc-Williams and Erin St Blaine for Adafruit Industries
A VL6180X sensor causes a sprite sheet animation to play
"""

import time
import os
import board
import busio
import displayio
from digitalio import DigitalInOut, Pull
from adafruit_matrixportal.matrix import Matrix
from adafruit_debouncer import Debouncer
import adafruit_vl6180x
# pylint: disable=global-statement
# Create I2C bus.
i2c = busio.I2C(board.SCL, board.SDA)

# Create sensor instance.
sensor = adafruit_vl6180x.VL6180X(i2c)

SPRITESHEET_FOLDER = "/bmps"
DEFAULT_FRAME_DURATION = 0.1 # 100ms
ANIMATION_DURATION = 5
AUTO_ADVANCE_LOOPS = 1
THRESHOLD = 20

# --- Display setup ---
matrix = Matrix(bit_depth=4)
sprite_group = displayio.Group(max_size=1)
matrix.display.show(sprite_group)

# --- Button setup ---
pin_down = DigitalInOut(board.BUTTON_DOWN)
pin_down.switch_to_input(pull=Pull.UP)
button_down = Debouncer(pin_down)
pin_up = DigitalInOut(board.BUTTON_UP)
pin_up.switch_to_input(pull=Pull.UP)
button_up = Debouncer(pin_up)

AUTO_ADVANCE = True

file_list = sorted(
[
f
for f in os.listdir(SPRITESHEET_FOLDER)
if (f.endswith(".bmp") and not f.startswith("."))
]
)

if len(file_list) == 0:
raise RuntimeError("No images found")

CURRENT_IMAGE = None
CURRENT_FRAME = 0
CURRENT_LOOP = 0
FRAME_COUNT = 0
FRAME_DURATION = DEFAULT_FRAME_DURATION


def load_image():
"""
Load an image as a sprite
"""
# pylint: disable=global-statement
global CURRENT_FRAME, CURRENT_LOOP, FRAME_COUNT, FRAME_DURATION
while sprite_group:
sprite_group.pop()

bitmap = displayio.OnDiskBitmap(
open(SPRITESHEET_FOLDER + "/" + file_list[CURRENT_IMAGE], "rb")
)

FRAME_COUNT = int(bitmap.height / matrix.display.height)
FRAME_DURATION = DEFAULT_FRAME_DURATION

sprite = displayio.TileGrid(
bitmap,
pixel_shader=displayio.ColorConverter(),
width=1,
height=1,
tile_width=bitmap.width,
tile_height=matrix.display.height,
)

sprite_group.append(sprite)
CURRENT_FRAME = 0
CURRENT_LOOP = 0


def advance_image():
"""
Advance to the next image in the list and loop back at the end
"""
# pylint: disable=global-statement
global CURRENT_IMAGE
if CURRENT_IMAGE is not None:
CURRENT_IMAGE += 1
if CURRENT_IMAGE is None or CURRENT_IMAGE >= len(file_list):
CURRENT_IMAGE = 0
load_image()

def advance_frame():
"""Advance the frame"""
# pylint: disable=global-statement
global CURRENT_FRAME, CURRENT_LOOP
CURRENT_FRAME = CURRENT_FRAME + 1
if CURRENT_FRAME >= FRAME_COUNT:
CURRENT_FRAME = 0
CURRENT_LOOP = CURRENT_LOOP + 1
sprite_group[0][0] = CURRENT_FRAME

def load_list_image(item):
"""Load the list item"""
global CURRENT_IMAGE
CURRENT_IMAGE = item
load_image()

def load_tipsy():
"""Load the .bmp image"""
load_list_image(1)

def play_thankyou():
"""load the thank you image"""
load_list_image(0)
while CURRENT_LOOP <= AUTO_ADVANCE_LOOPS:
advance_frame()
time.sleep(FRAME_DURATION)


advance_image()

while True:
if sensor.range < THRESHOLD:
play_thankyou()
else:
load_tipsy()

Pixel Art Specs

If you want to create your own artwork for display, these are the specifications to follow.

For the still .bmp image:

  • Images should be a maximum of 64 pixels high
  • Images can be up to 32 pixels wide
  • Colors are 16-bit or 24-bit RGB
  • Save files as .bmp format
  • Since the orientation of the tip jar is vertical rather than horizontal, rotate your image 90% clockwise before uploading it.

We've found that crisp images (not too much anti-aliasing) work best.

We have a whole page on Pixel Art Fundamentals here!

For the Sprite Sheet:

A Sprite Sheet is like a filmstrip: a vertical series of animation frames saved as a single .bmp. Our code will parse this into animation frames and play them back at the speed you specify.

Check out this guide for detailed instructions on building your own a sprite sheet with Aseprite.

How it Works

Libraries

Here's how the code works. First, we import the libraries:

Download: file

Copy Code
import time
import os
import board
import busio
import displayio
from digitalio import DigitalInOut, Pull
from adafruit_matrixportal.matrix import Matrix
from adafruit_debouncer import Debouncer
import adafruit_vl6180x

Next, we set up the sensor:

Download: file

Copy Code
# Create I2C bus.
i2c = busio.I2C(board.SCL, board.SDA)

# Create sensor instance.
sensor = adafruit_vl6180x.VL6180X(i2c)

Variables

Then, we'll set the variables for DEFAULT_FRAME_DURATION (how quickly we move through the sprite sheet) and ANIMATION_DURATION (how long each animation stays on the screen). AUTO_ADVANCE_LOOPS determines how many times your sprite sheet plays through. And we'll set up the path to the image folders.

The THRESHOLD variable is the distance in mm between your sensor and the edge of the money slot. If your tip jar isn't reacting, try increasing this number a bit. Or, open your serial monitor in the Mu editor for a readout from the sensor to see exactly what readings you're getting.

Download: file

Copy Code
SPRITESHEET_FOLDER = "/bmps"
DEFAULT_FRAME_DURATION = 0.1 # 100ms
ANIMATION_DURATION = 5
AUTO_ADVANCE_LOOPS = 1
THRESHOLD = 20

Display/Pin Setup

Next, we set up the display and the pins used for the buttons. We aren't using the buttons for anything in this code sample, but they are set up for you in case you want to add button functionality.

Download: file

Copy Code
matrix = Matrix(bit_depth=6)
display = matrix.display

pin_down = DigitalInOut(board.BUTTON_DOWN)
pin_down.switch_to_input(pull=Pull.UP)
button_down = Debouncer(pin_down)
pin_up = DigitalInOut(board.BUTTON_UP)
pin_up.switch_to_input(pull=Pull.UP)
button_up = Debouncer(pin_up)

Functions

Next, we'll set up our functions. These will govern the loading and playback of the images.

Download: file

Copy Code
def load_image():
"""
Load an image as a sprite
"""
# pylint: disable=global-statement
global CURRENT_FRAME, CURRENT_LOOP, FRAME_COUNT, FRAME_DURATION
while sprite_group:
sprite_group.pop()

bitmap = displayio.OnDiskBitmap(
open(SPRITESHEET_FOLDER + "/" + file_list[CURRENT_IMAGE], "rb")
)

FRAME_COUNT = int(bitmap.height / matrix.display.height)
FRAME_DURATION = DEFAULT_FRAME_DURATION

sprite = displayio.TileGrid(
bitmap,
pixel_shader=displayio.ColorConverter(),
width=1,
height=1,
tile_width=bitmap.width,
tile_height=matrix.display.height,
)

sprite_group.append(sprite)
CURRENT_FRAME = 0
CURRENT_LOOP = 0


def advance_image():
"""
Advance to the next image in the list and loop back at the end
"""
# pylint: disable=global-statement
global CURRENT_IMAGE
if CURRENT_IMAGE is not None:
CURRENT_IMAGE += 1
if CURRENT_IMAGE is None or CURRENT_IMAGE >= len(file_list):
CURRENT_IMAGE = 0
load_image()

def advance_frame():
"""Advance the frame"""
# pylint: disable=global-statement
global CURRENT_FRAME, CURRENT_LOOP
CURRENT_FRAME = CURRENT_FRAME + 1
if CURRENT_FRAME >= FRAME_COUNT:
CURRENT_FRAME = 0
CURRENT_LOOP = CURRENT_LOOP + 1
sprite_group[0][0] = CURRENT_FRAME

def load_list_image(item):
"""Load the list item"""
global CURRENT_IMAGE
CURRENT_IMAGE = item
load_image()

def load_tipsy():
"""Load the .bmp image"""
load_list_image(1)

def play_thankyou():
"""load the thank you image"""
load_list_image(0)
while CURRENT_LOOP <= AUTO_ADVANCE_LOOPS:
advance_frame()
time.sleep(FRAME_DURATION)

Main Loop

Since we did most of the heavy lifting in the functions, our main loop is really simple. Check the sensor and see if the THRESHOLD value has been triggered (if someone puts a dollar into the jar). If so, the Thank You animation will play AUTO_ADVANCE_LOOPS times through, then it will reset to playing the tipsy image.

Download: file

Copy Code
while True:
if sensor.range < THRESHOLD:
play_thankyou()
else:
load_tipsy()

Uploading & Testing

Save your code to the CIRCUITPY drive on your computer as code.py, at the root of the CIRCUITPY drive. The code will start to run automatically.

If you see a "blinka" error message, here are some things to try:

  • Have you installed all the libraries?
  • Are you running the latest version of CircuitPython?
  • Are your .bmp images uploaded to a folder called /bmps?

If it's still not working, check out this guide for more troubleshooting tips.

Build the Tip Jar

Remove any labels or stickers from your jar. Goo-Gone works well for this. Put the jar on top of the RGB matrix and draw vertical cut lines with a permanent marker along the edges of the matrix.

jar_20

Be extremely careful using any cutting tool and wear appropriate clothing and take necessary precautions.

Use a box cutter or rotary tool to carefully cut along the cut lines, creating an open "flat" area to attach your RGB matrix.

cutter_21

cutter_22

Clean up the edges with flush cutters or a grinder, if needed. Try to get them as straight as possible. The jar should lay perfectly flat on the table without wiggling, if you put the cut side down.

Cover the raw edges with a piece of 1" gaffer's tape.

edges_24

edges_23

If your jar is the same height or shorter than your RGB matrix, you'll need to modify the lid as well. Put the lid on the jar and mark your cut line, then cut the lid to size with a saw or rotary tool.

Use a rotary tool or heat tool to make an opening to drop the money in.

jar_25

Attach your sensor to the underside of the lid with the laser pointing toward the opening. Place it within 20mm of the opening if possible - that way you won't need to modify the sample code.

If your build requires a different alignment, you can modify the code without too much trouble.

sensor_26

Attach the RGB matrix to the back of the jar with the lights pointing inwards. Be sure to line it up evenly on the bottom so the jar doesn't tip over - it is a little bit back-heavy when it's not full of money. (So, let's get on with it, and get those quarters rolling in!)

attach_27

If you've already uploaded the code, test it out by dropping some coins or bills through the slot. Each time a tip is dropped in, you will see a Thank You animation on the pixels.

test_28

Powering

Power the project via the USB port on the Matrix Portal. You can plug directly into a power supply (like this one), or plug in a USB battery if you're busking outdoors and need a mobile tip jar.

Key Parts and Components

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