Solid State Alarm Clock with battery back

Clock dimensions - 160mm high, 150mm wide, 60mm deep - 130mm clock face.

Background of project

Originally based on used filaments taken from LED lamp that blew up for building my first clock. The ones I took out required seventy volts and using the Arduino to generate a square wave to drive a transformer to run them.

I have since I found these filaments to be available on Aliexpress. You can get all voltages and colors, but for this design I plumbed for three volt filaments driven directly by the Arduino. This enabled me to need no external drivers. By multiplexing and pulse width modulation the Arduno Nano is more than capable of driving these lamps. In fact the Arduino will not be damaged if while designing such systems the multiplex stops.

Features of the clock

1) A solid state analogue clock

2) A clock that is truly twenty four hours, allowing an alarm to be set over the twenty four hour period (not twelve as you’d get with a wind up alarm)

3) Adjusts brightness of the display, making a great night light

4) Both minutes and seconds displayed

5) No moving parts

6) Choice of two clock battery backed modules for standard accuracy, or very accurate.

7) Very easy to construct.

8) Runs from any USB outlet or adapter, be it on a main socket, or even your computer.

9) Remembers the time as well as the clock settings and alarm time if left unplugged

Let's look at the features and how it displays:

The minute hand steps every five minutes. The four minutes between the five minute steps are displayed in the center of the clock face. Second are displayed on the outer circle, flashing once every five seconds.

Hour Time

Set up by the hour is using push buttons. To set the twenty four hour clock 1 to 12 hours step round the inner circle. 13 to 24 hours steps round on the outer circle. During normal operation the twenty four hours is not displayed only the twelve. However, we only need the twenty four hours to set up the alarm time.

Minute Time

Setting up the minutes is using a second button. You can set it dead on a five minute position or for example, twelve minutes is set by the minutes in the ten minute postion, adding the extra minutes by the central minutes lights.

Alarm Time

Setting the alarm time, press the alarm time button. This will display the alarm time. While in alarm time use the hour and minute buttons to set the time of alarm. Once the alarm time is set, no longer touching of the buttons, the clock will revert to the current time.

The alarm armed light in the central positron of the clock will indicate if alarm is set. A quick press of the alarm button will display the alarm and switch it off. Press again and the alarm button will come back on. When the alarm sounds, pressing any button will stop it, or it will silence after one minute.

Construction

I have supplied a circuit diagram, a PCB layout, construction notes and programme. You are welcome to use my information to construct your own clock. All parts are readily available off the internet.

 If you want to construct the same case, they were built in Fusion for my Ender3 and I have stl files available.

Note 1 Take care with the voltage generator module. It can arrive to you set up at 36 volts. It must be adjusted down to around ten volts before powering the Nano, or damage may occur.

Note 2 The filament frames were made on a 3D printer, apart from making them secure, they are intended to stop light escaping to the sides. You can use U channel, but take care some rubber channels are conductive and will upset your circuit operation if shorting to the pcb board.

Note 3 The plastic glass front was smoky gray hiding all the PCB joints very effective size 145mm x 145mm

Note 4 While you can design your own case, case construction is very easy, simple and low cost. A 3D printer is essential and the whole case-making time can be done in a couple of hours.

Note 5 The filaments are very easy to break while constructing. Once in the holders they take some breaking. Be careful they are diodes so they do have a + and - pin. The positive pin is indicated with a tiny hole in the strip. Test before you solder in by very carefully try to bend it. If it bends easy then it is broken and no use. They cost very little, so always buy more than you need, often you get ones arrive already broken, then you are bound to break one yourself just handling them.

 Complete Parts List

1) Arduino NANO

2) Clock module RTC12c

3) Inverter MT3608

4) PCB

5) Blue LEDs x 13

6) White LEDs x 4

7) Filaments x 24

8) Resisters 10k x 2

9) Resisters 220ohm x 3

10) Buzzer 5 volt

11) Buttons and caps x 4

12) IC holder strip 32 way

13) Capacitor 10mfd 25v

14) Solder 1m

15) Nuts and bolts 3.5mm x 4

16) Nuts and bolt  2 mm x 1

17) Filament holder x 12 (make in 3D see notes for alternatives)

18) Centre disk (make in 3D use the five hole version for the alarm)

19) Inverter cover

20) Arduino cover

21) Front corner x 4

22) Foot with cable clamp

23) Foot with no cable clamp

24) Perspex glass (grey tinted 145mm x145mm x 3mm)

25) 2m cable

26) 4 Button assembly

The following PDF files are the construction stages. I have included the construction of my version of the case. Using 3D printed corners and a back stand, construction is based around a 145mm x 145mm x 3mm piece of perspex. I can supply the 3D STL files for your printer if required.

The printed circuit board should be constructed and tested first. You will find assistance in testing the board after uploading the file on the serial monitor. I used the old 32P old boot logger. Check your Nano version and adjust if required.

The booster module MT3608 is available everywhere. I use one as USB five volts into NANO is too low through the onboard regulator. Far better to boost the voltage to about ten volts, this allows for fluctuation and the NANO runs far more stable. Set the voltage up before plugging in the NANO as they often come set around twenty odd volts. I just plug a USB in on it and put a meter on before I even fit it to the board.

Be careful with the filament lights. Once in the holder and soldered they are really good and reliable, as we under run them. But the LEDs are mounted on a plastic rigid strip and are very easy to fracture. Look at the construction notes for + and -, the tiny hole indicates +.

Push button switches are easy to obtain, everyone sells them. I have on the PCB given two pin solder points for each switch if you decide on a another type of case.

The clock module uses the low cost RTC12C, however, I find after a few months it looses time and needs resetting. That's okay, but the PCB allows you to use as an alternative the more accurate DS3231. Both fit, only the small 3D printed bracket changes.

The small sounder is pretty standard anywhere. Use the 5 volt one the clock does not send out a frequency to generate the sound.

The disc in the center of the clock is shown as four holes, but there is a five hold version, so the alarm armed LED can be displayed. I only have it a .stl file and it won't download.

Build it and use the program supplied and it will work fine. I developed it over the lockdown and made a few clocks for friends, they are all working great. Enjoy.