Electronic chimes

[Berry Greene]

Its a question really. a Modern MDF Wall clock with all electronic plastic parts. The pendulum is a plastic replica of a grid-iron driven by an electronic unit. The Chimes are a separate little plastic box activated by a switch from within the quartz driven movement. That movement has a switch activated by a plastic cam on the train which turns on the hour. Ah but is this crude little spring contact job a NO or NC device? {Normally Open circuit or Normally Closed Circuit}.
The chime works but the switch seems to bounce or stutter. It needs some anti-bounce in the electronics - but doesn't seem to have it. In order to get it working at all I had to "dress" the contacts and it seemed to me that the cam opens them and its the closing when it drops off the cam that activates the chimes. However, the chimes set off and then restart after the chime and during the strike sequence. That upsets the synching to the hour. (Number of strikes).
Have I misunderstood something here? Any help would be gratefully appreciated. Rgds BerryG

 

[Berry Greene]

I am going to answer my own question here.
Upon examining the micro-switch further I had to deduce that the action is neither N/C or N/O. This guy needs to be NN/O (Nearly Normally Open!). To counter the bounce problem the cam actually widens the N/O contacts and allows it to ping to momentary closed contact that is immediately open again. You cannot measure this brief encounter with a normal continuity meter as it is so brief.
Interesting solution. As a retired electronics engineer with an interest in (mainly mechanical) clocks, I was bound to think in terms of a true anti-bounce solution such as those I am used to. This is not a "can't fail" solution because these contacts could still bounce. The adjustment is so fine and depends on forming (bending) the switch contacts which are strips of spring metal. Probably gold plated copper. "Twang" it goes and with luck produces a wide enough single pulse to trigger a chime sequence with requisite number of strikes.
A button on the side of the music module steps it through a 24 hr sequence where between the hours of 22:00 and 05:00 there is no chime or strike. {Last strike is 9pm. First strike is 6am}. This is how you "Synch up" the real time to the correct number of strikes.
All that is needed now is fine tune the hands to the hour and all will be well. Won't it? You want picture? I post picture. You see its not bad looking - but its innards lack anything of traditional quality. Wife likes it. What does she know....?

Rgds BerryG