Review: A kit for the Elektor Alarm Clock with 3-way Display

Update!

My clock came with firmware version 2.1.3 installed. This is also available as a free download on the project support page. It contains all the necessary libraries for compiling the sketch yourself, and the finished Arduino sketch. There is now another firmware version, which can be downloaded by clicking on ‘Labs-Article ...’ on the web page. Here is another link to the current version 2.6.3. In addition to the Arduino sketch, this archive also contains the hex-code file of the firmware as well as a version with an integrated Arduino bootloader. It’s an old habit but I always like to install the most up to date firmware on my devices, so I did that here also. That gives me something practical to do and makes up for the fact that I didn’t need to get out a soldering iron...
 
 

Programming

The clock does not have a USB port and it’s not just a modified Arduino board with a display either. Consequently, to upload an update or make your own changes to the ATmega328P using the Arduino IDE, you will need to pop the chip out of its socket and plug it into a standard Arduino Uno board. I rummaged around on the shelf where I keep all my development boards. I found some Arduino variants but unfortunately they all used soldered, SMD-outline microcontrollers.

 

There is however an alternative: The clock board is fitted with the standard Atmel 6-pin programming header which means I can use the AVR AVRISP mkll programmer (or a clone) to program the chip from the Arduino IDE. This programmer does not supply power to the target board so there is no problem with the clock circuitry running at 3.3 V. An external 5-V supply connected here would kill the on-board supercap for sure. The 1-Farad supercap stores enough energy to keep the integrated real-time clock functions running for three days. This was a good excuse also to update my Arduino IDE studio installation to the latest version (version 7). For anyone who has experienced driver problems when using the programmer with previous versions running under Windows 10, you just need to install the new version 7, plug the AVRISP MKII in and everything should be fine. I used the hex file with its built-in boot loader, in case I want to run it from the Arduino IDE.

 

Time display format

The alarm clock is advertised as a ‘3-way display’ unit. In addition to the character-based display already shown, there are two other display modes. The picture opposite shows the alarm clock with the look of a 7-segment display (running under firmware version 2.6.3). You can also have a simulated analogue clock face with coloured hands, if you want.
In the unmodified standard version of the firmware, these displays will change. To prevent this you will need to inhibit it in the code. The source code is well documented so it’s easy to make the necessary changes. You can thereby set your preferred display mode and also implement a completely different version if you want to. The language used on the display ​​can also be changed in this way. In addition to English you can choose French, Italian or German.

To bed, to bed...

The setup procedure is really easy so I set it to wake me up the next day. The built-in buzzer volume was just about right for me: not too strident but at the same time loud enough to wake me up. This may not be the case for everyone, teens are notoriously difficult to rouse when it comes to getting to school on time… they generally need something a bit more…  explosive?

 

Incidentally, current consumption at maximum brightness was measured at 78 mA. With the 9-V power unit supplied this works out at 0.7 W when the display is at maximum brightness. In a normal domestic setting the brightness will be adjusted automatically so we can reckon on an average power consumption of about 0.4 W. Assuming the AC power adapter has an efficiency of around 80% over 365¼ days the alarm clock will therefore take approximately 4.4 kWh per year. The circuit uses a 3.3 V regulator with a series diode to protect against reverse voltage connection.
The voltage drop generated by this diode implies that operation from a 5.0 V power supply would be marginal. A 6 V supply should however supply enough voltage for the regulator to operate reliably and would give an energy saving of around 33% over the 9 V unit. I also ran the clock from a mains USB mobile phone charger which usually outputs at least 5.1 V. Mine was measured at 5.2 V and that was enough for the 3.3-V regulator.

I like the clock, all I need now is a case to ensure that it tastefully blends in with the rest of my mother’s bedroom decor.
The only criticism I have is the lack of labeling around the 6-pin programming header on the PCB. I have identified pin 1 in the above picture showing the disassembled clock.
Now, I just need to find a nice case...
  The Alarm Clock with 3-way Display is available from the Elektor Store here.