The CountClock has two features: firstly, time can be told by counting the LEDs and secondly it has multiple learning levels that simplify the confusing characteristics of a normal analog clock. The CountClock's target audience is mainly composed of children aged 2 to 7 years old.

The CountClock has been presented in a Meta Instructable and has various separate Instructables explaining a number of aspects in more detail, among others it explains why analog clocks are confusing for children en how the CountClock concept addresses these shortcomings.

The current Instructable is the detailed Instructable regarding CountClock Hour and Minute Prototype.

The control of the LEDs is being done by an Arduino board (Sparkfun Arduino Pro) with nine shift registers attached and a potentiometer for dimming. The last step in this Instructable elaborates on the lessons learned from this project. Make sure that you don't skip those lessons!

Note: the prototype documented here has a follow-up version, which is presented here: CountClock Hours and Minutes.

Step 1: The Concept Behind CountClock Hour and Minute Prototype

In order to introduce the learning step from hours (known through the CountClock Hours Only Prototype) to a higher time resolution it is required to display minutes. This was done by adding a second circle to the layout of CountClock Hours Only Prototype, with 60 LEDs that can be individually controlled.

Lessons learned from CountClock Hour & Minute Prototype are:

The concept of the learning steps was confirmed to work as expected.
People of all ages really like the wooden CountClock CountClock Hour & Minute Prototype
There might be a market for the CountClock as a kit or as an off-the-shelf product.

The following learning levels are available from CountClock CountClock Hour & Minute Prototype:

Learning Level 1: only the hours in a cumulative manner (similar to CountClock Hours Only Prototype);
Learning Level 2: the cumulative hours and the half hours (i.e. twice cumulatively 30 minutes);
Learning Level 3: the cumulative hours and the quarters (i.e. four times cumulatively 15 minutes);
Learning Level 4: the cumulative hours and ten minute intervals (i.e. six times cumulatively 10 minutes);
Learning Level 5: the cumulative hours and five minute intervals (i.e. twelve times cumulatively 5 minutes);
Learning Level 6: the cumulative hours and cumulative minutes (with also the seconds highlighted);
Learning Level 7: the hours and minutes (not cumulatively, and with the actual second highlighted);

The animated pictures above show Learning levels 1 and 3. More info on the learning steps can be found in the Instructable introducing the follow-up version of this prototype: CountClock Hours and Minutes.

The design consists of a button on the back of the CountClock CountClock Hour & Minute Prototype with which the learning levels can be selected (note that although the hardware was prepared Arduino source code does not include the button support, sorry).

The next steps show pictures of the making of the CountClock Hour & Minute Prototype.

Step 2: Making Electronics of CountClock Hour and Minute Prototype

The pictures above show the making of the electronics inside CountClock Hours & Minutes Prototype.

The next step shows the making of the housing.

Step 3: Making the Housing of CountClock Hour and Minute Prototype

The pictures above show how the housing was made.

The next step elaborates on the lessons learned. Read the the next step first before starting your project!

Step 4: CountClock Prototype Lessons

The control of the LEDs is being done by an Arduino board with 9 shift registers for controlling 72 LEDs (12 for the hours and 60 for the minutes). Lessons learned in the making process and worth sharing are listed below:

Since the work is taking place on the backside of the front panel, all LEDs are placed mirrored. In order to keep this continuously in mind, it is a good idea to use markers indicating where each LED is to be placed. See the yellow numbers in the first picture, which run counterclockwise.
Dimming the LEDs with a variable resistance (potentiometer) gives good results, at the expense of a larger energy consumption; Powering the CountClock with rechargable batteries is possible but not for long times. With four AA-sized rechargable batteries (2400 mAh) the clock would run for a number of hours, but not a full day. The CountClock was hooked up to a 5V USB power supply all day. See second picture;
The yellow button was meant to control the learning levels and to adjust time. In this CountClock Hour & Minute Prototype that functionality never became reality, in practice the CountClock was reprogrammed at every learning level. See second picture;
For unknown reasons the solenoid (see third picture) didn't work, so the bell never stroke the hour as was designed. This part of the Arduino source code never was confirmed to function. For the commercial uptake of CountClock commercial electric designers strongly discouraged including a real bell, they preferred a buzzer. However, a buzzer is a poor alternative for a bell, which is still included in CountClock final version (see CountClock Hours and Minutes);
CountClock Hours Only Prototype (documented here) worked fine from the first moment. This new CountClock Hours & Minutes Prototype however involved so much soldering that a few connections were faulty. To make things worse, all LEDs were already connected and the PCB was already mounted in the wooden dial, so debugging the hardware took a considerable amount of time. See the last to pictures above to find the solution (the red and yellow wires were soldered to shift register legs directly). Lesson: before building in your PCB, first check all soldering work! ;
Just like for CountClock Hours Only Prototype, for keeping the exact time a separate module would be required (a real-time clock, for example DS1307). This Prototyping II doesn't have one so every hour a time was corrected a few seconds (the deviation observed was 72 second per day, so 3 seconds per hour). Alternatively, resetting the CountClock every now and then is also an approach.The next step discloses the Arduino source code of CountClock Hour & Minute Prototype.

So, looking back at this project, is it a recommendable approach to drive 72 LEDs via shift registers? If the purpose is to have some soldering practise: perhaps. For driving the 12 LEDs in the CountClock Hours Only Prototype the shift registers were a good choice. For the CountClock variant with the 72 LEDs, it is easier to refer to the Neopixel LED series, which offers off-the-shelf LED rings with integrated drivers. This has been used in the CountClock Hours and Minutes version.

There's one more remark still to make: conventional LEDs, encapsulated in epoxy, at the same time act as a lightpipe, allowing to transmit the light from the inside of the CountClock towards the front. For aesthetic reasons, it could be a good idea to use RGD conventional LEDs with a separate driver. This is a serious option to be considered when thinking about upscaling the CountClock manufacturing. In the process of trying to find commercial manufactures for the CountClock production (outcome: this search failed) this was one of the issues discussed.

An address to the reader: if you have suggestions where to manufacture the complete CountClock electronics (possibly using conventional RGB LEDs encapsulated in epoxy) this is highly appreciated. The idea is then to combine this with the CountClock Housing as presented for the CountClock Hours and Minutes. And before forgetting: preferably using open source licenses and, if reasonably achievable, including all certification required...

Thanks for reading!