11

FORGE

Next, you will need to add your Telegram Bot
token, your Google Maps API key, and your home
location. Finally, if you are not in the UK or Ireland,
you will more than likely need to change your time
zone. Uncomment the appropriate time zone and
comment out the UK and Ireland time zone.

WHAT MAKES IT TICK
You’ll need to wire everything together as shown
in Figure 1 (overleaf). The LEDs are addressable
RGB LEDs, so they only require a single GPIO pin
of your microcontroller and you can set the colour
of each LED individually. The input of the first LED
(the one over on the left when looking at it from
the front) will be connected to the Wemos, and its
output will be connected to the input of the second
LED. For all subsequent LEDs, the input of the next

LED is connected to the output of the previous one.
The output of the final LED will not be connected to
anything. Soldering these LEDs should be left until
the final assembly stage.

CREATING THE MOUNT
Take the back panel off the picture frame and use
it to trace a square onto your foam board. Using a
sharp blade, cut out the square.
Next, you’ll need to separate the panels from the
display, as you’ll be placing the PCB on the back side
of the foam and the panels on the front; this will hold
the display in place and hide the cuts from view.

Carefully remove each of the dot matrix panels

from the dot matrix display. There are markings on

the side of each of the dot matrix panels; make a

note of what direction they are facing in comparison

to the PCB to ensure they are put back in the

correct orientation.

If your PCB has header pins attached, desolder

and remove them. Replacing these with wire will

make the PCB fit flush to the foam board.

Measure the rectangle created by the pins and

mark out that shape where you want to place it on

the foam board. The objective is to cut out a shape

that the pins of the PCB will fit through, but the PCB

itself will be too big for.

The LEDs for this project are all on an arc around

the centre point of the servo. Mark where you want

the centre point of the servo arm to be and, using

your compass, draw a semicircle lightly for where

you want the LEDs to be.

You can often have issues using NeoPixel LEDs with

a 3.3 V logic level device such as an ESP8266 or

Raspberry Pi. You can get around this issue by using

a logic level shifter to convert the 3.3 V to 5 V for the

Data In connection for the first LED. However, we’ve

found that it works fine with just a small capacitor

between Data In on the first LED and Ground (as seen

in this project).

Once you are happy

everything is working

correctly, secure the

components in place

with some hot glue

”

”

Above

A peek at what’s

hiding at the back

If you are short

on time, or just

interested in

quickly trying

this project out,

strip it back to

be just the dot

matrix display,

the Wemos D1

Mini, and use

DuPont cables

to connect them

together. The

key piece of

functionality,

displaying the

expected arrival

time, uses only

the display.

SHORT

ON TIME?

NEOPIXELS WITH A

3.3 V DEVICE