This time I present you a color wall analog clock for kids design using LED strips.

The basics of the clock is to use three LED strips and different colors to show the time:

In the round led strip, the green color is used to show the hours, the red color to show the minutes and the blue color to show both, the hours and the minutes
In the 4 leds strip, in red color, each led represents one minute we have to add to the minutes marked by round led strip
In the 6 leds strip, in purple color, each led represent 10 seconds

The clock is mounted on a transparent plate and it is builded to easily mount and unmount it on different color plates.

A DS3231 Real Time Clock module is used to maintain hours, minutes and seconds.

The clock is powered by a 3,7 V battery you can charge using a micro USB charger.

It looks very nice in the darkness. I hope you like.

Supplies

Arduino NANO or compatible microcontroller
Adjustable DC to DC step-up voltage boost converter
DS3231 Real Time Clock module
An old movil battery 3,7 V 1000 mAh
Micro USB charger for battery
60 Leds strip
Double sided PCB
Transparent Plastic Color Plates
Wires
Soldering kit
Cardboard
Compass
Protractor

Step 1: Soldering the LED Strips

Using my cutting pad, a protractor and a compass, I drew the clock sphere and the position of the hours.

The diameter of the sphere must be the same that the ones of the plastic plate where you are going to mount your clock.

In the second image you can see the round LED strip. All the leds has been soldered one by one to form the sphere of the clock. You have take into account the little arrow you can see on each led to solder them in the right way. I have used a green cable for the data pin, a red cable for the 5V pin and a black one for the ground pin.

In the third image you can see a test of all the LED strips before to mount in the clock

Step 2: Glue the LED Strips in a Cardboard Base

Cut a spherical piece of cardboard. Open two little holes in the cardboard to pass through them the three cables of each LED strip.

Step 3: Wire and Connect the Electrical Components

The steps I followed has been the following:

Solder a 330 ohmios resistor to the extreme of the data cable (green cable) of each LED strip as you can see in the first image
Join all the 5V cables
Join all the ground cables
Solder the microcontroller, the step up boost converter, the micro USB charger, the DS3231 module and the little switch on the doubled side PCB
Connect the micro USB charger to the battery (it is placed under the PCB)
Solder the round strip data cable to the D2 pin in the microcontroller
Solder the 6 LED strip data cable to the D3 pin in the microcontroller
Solder the 4 LED strip data cable to the D4 pin in the microcontroller
Solder the SDA pin of the DS3231 module to the A4 pin in the microcontroller
Solder the SCL pin of the DS3231 module to the A5 pin in the microcontroller
Wire and connect the step up boost converter to the micro USB charger as you can see in the second image
Adjust the step up voltage converter to 5 V output
Wire and connect a little switch to control the power as you can see in the image

You have take into account the following: the high of the electrical circuit must be less than the plate depth to allow to hung up the wall clock without problems

Step 4: Set the Time

The DS3231 Real Time Clock module maintains the time because it uses a external battery, but if you haven´t got one, I have included the following code to set the initial time:

// set the time
int gminutes = 10;
int ghours = 3;
int gseconds = 0;
// end set time

The variable brightness, in the code, controls the intensity of all the strips in the clock.

WallClock.rar
Download

Step 5: Choose the Color and Mount the Clock

Cut several cardboard pieces to fix the hardware to the plate and hang up it wherever you want.

Step 6: How to Read the Time

Image with the label "03:34:10"

In the round LED strip, the leds placed between 12 and 3 are on (green color). It means, it was 3.
In the round LED strip, the leds between 4 and 6 are on (red color). It means, it was 3:30, but in the 4 leds strip, all the leds are on, so really it was 3:34.
The first led in the 6 leds strip is on (1 x 10 = 10 seconds), so it was 3:34:10 at that moment

Image with the label "03:10:30"

In the round LED strip, the led in 3 is on (green color). It means, it was 3.
In the round LED strip, the leds between 12 and 2 are on (red color). It means, it was 3:10.
The third led in the 6 leds strip is on (3 x 10 = 30 seconds), so it was 3:10:30 at that moment

Image with the label "03:16:10"

In the round LED strip, the leds placed between 12 and 3 are on (blue color). It means, it was 3:15, but in the 4 leds strip only the first led is on, so really it was 3:16.
The first led in the 6 leds strip is on (1 x 10 = 10 seconds), so it was 3:16:10 at that moment