Tap: no reaction

[dub]

Hi!

My daughter (10) and I just built the metronome kit, and there is a problem.
When the metronome is turned on, the following happens:
- display flashes brightly;
- "r22" is displayed for 1/2 second;
- "tap" appears on the display
(display seems to "shimmer": brightness changes rapidly and slightly?)

Taps are not being registered; not gentle ones, nor rough ones, nor banging
the whole thing on the table Display never goes bright.

How do I troubleshoot this? What should I look for? Busted buzzer?

Of course, the kit is completely built, so all the soldering is covered by the
battery holder, which is glued and soldered to the PCB

Any help is appreciated.

Thanks!

[layne]

Does it beep when you flip the power switch? It should beep when the r22 is displayed on the digits. Sounds like you something is wrong with the piezo, especially since it's not recognizing your taps.

The display "shimmer" also sounds problematic, maybe a loose connection to the transistors driving the displays? When you wave the metronome around in the air when it's displaying "TAP", does it look anything like this? Can you see the separate digits being displayed one-at-a-time?


I really need to go back to the build instructions and add a step in there, "before you solder in the battery holder, hold it in place and make sure everything is working right (beeps, displays, buttons, etc). It's much easier to fix a bad solder connection before you put the battery holder on the back!"

[dub]

No; the thing does not beep when turned on.
That's a clever trick - to make it beep on power on. You may want to mention it in the documentation

The "shimmer" that I see is probably the individual digits being turned on and off.
I did not realize that you a driving them one-at-a-time; come to think of it, there aren't enough pins to
drive them all-at-once...

When I wave the metronome, it looks exactly like on your picture - which is, I assume, normal?

It looks like I need to desolder the battery holder, but how do I troubleshoot the buzzer?
Basically, can I figure out that it is the buzzer, and not some to it, before I remove the buzzer?

Thanks!

[dub]

Found it!
It turned out that when assembling the kit I damaged (burned?) the short trace between the resistor and the buzzer ("P").
I patched it, and everything is working fine.
(Of course, I removed the buzzer first, destroying it in the process, before figuring out what the problem was, and had to put another one in.)

Thank you for your help - and for the great kit!

[layne]

Glad you got it figured out. Yesterday I re-worked the build instructions to include a step about test-fitting the battery holder so you can test everything before you solder down the battery holder. Thanks for the suggestions, glad you were able to find another piezo!