A small hitch

After the first powering up of the Arduino and the shield, and well before the final assembly, the servos are placed in the mid position by the program (sketch). The manual suggests to verify the servos individually before continuing. It’s an advice which I recommend to follow, you’ll see why after reading the following.

If you have never connected an Arduino to your computer, and if it does not appear after starting the IDE, have a look at the port setup in the Tools menu.

When the time comes to communicate with the Arduino via the serial monitor, this will give an error message (Invalid settings in EEPROM) which is not surprising, because the first time, there are no default values in the EEPROM. On this point also, the manual is clear.

 
R3 Like a dislocated tombstone.
 
After assembly, when I came to calibrate the mechanics, I saw that the right servo was not responding at all. As the version of the manual that I used did not (yet) recommend verifying the workings of the individual servos before assembly, I hadn’t done so. So I had to disassemble it to verify it, by doing a simple test which consisted of exchanging the servos G and D; this showed that servo D was powered up but did not receive any signal from the Arduino. After some research and checking with a magnifying glass, it appeared that R3, one of two resistors which pulled up the outputs of the Arduino to the servomotor, was badly soldered.

The problem was resolved with a touch of the soldering iron! So add a magnifying glass to your list of tools, even if the possibility of a misadventure like mine is very small.

In the course of repeated manipulations during the course of this faultfinding, I found that the USB cable was a little short. To facilitate my maneuvers, I found one which was longer. The cables to the vibrating motors were not long enough to comfortably rest the tray of sand flat (with the sand in it). One solution would be to lengthen these wires. I didn’t do it, because disassembly is an awful lot of work.
 

Conclusion

This kit is a beautiful project in every respect. The clock does exactly what it is supposed to do… and even a bit more, because in smoothing the sand it emits every minute an unmistakable sound! It’s a fascinating gadget for children and adults alike. The program (sketch) is not only richly commented, but offers in addition a number of commands for the pantograph and some drawing functions which have nothing to do with the sand clock. If you are not interested in those yourself, I’m sure you will find someone in your circle who will enjoy discovering these functions.

The fine-tuning of the servo calibration to control the stylus is an interesting exercise once the assembly is finished. One is easily drawn in to this and it’s as good a way as any to start programming with the Arduino. It seems to me that not the least of the merits of a gadget like the sand clock is to draw attention to these possibilities.

Realizing a happy marriage between clever mechanics, electronics and programming with the Arduino sauce, this amazing kit seems to me to offer an excellent support for beginners.

Stop Press: I have learned that due to a software bug (which passed unnoticed by me) some clocks sometimes start tracing the time before the usual minute’s wait is up. The designer confirms that this erratic behavior, happily rare to her knowledge, will be eliminated in the next version of the software, currently being prepared. She has not discounted the possibility that the cause is a furtive reset of the Arduino, provoked by electrical interference interference from one of the servos. Cure: swap the two servos or pass their wires several times round a ferrite bead.  Update: Problem solved!