Really, are you sure its not just that someone started them all off by
walking down the row and switching them on?

Brian

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"Tim+" wrote in message
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How to they get a line of them to all blink in a "cascade"?

I'm guessing some sort of Bluetooth link and some software to control
triggering but I'm not sure what initiates the cascade and what stops it
running backwards.

Tim

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On Wed, 25 May 2016 07:53:18 +0100, Brian Gaff wrote:

Really, are you sure its not just that someone started them all off by
walking down the row and switching them on?

These lamps produce a visual illusion of a light moving along the
line of the lights. Actually it's several lights all "moving" in the
same direction and six positions apart.

If the lamps all free ran they wouldn't stay synchronised enough to
produce the constant visual effect. Well not without spending a
relatively large amount on an accurate clock in each one.

"Accurate" meaning that they all tick at the same rate *and* all
drift by the same amount due to temperature or WHY. IIRC the step
time between lamps is 200 ms if that changed by more than 20 ms I
think it would be very noticeable. 20 ms over 24 hours is 1 part in
4.32 million. That's not easy to consistently mass produce.

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Cheers
Dave.

On Wednesday, 25 May 2016 09:20:58 UTC+1, Dave Liquorice wrote:
On Wed, 25 May 2016 07:53:18 +0100, Brian Gaff wrote:

Really, are you sure its not just that someone started them all off by
walking down the row and switching them on?

These lamps produce a visual illusion of a light moving along the
line of the lights. Actually it's several lights all "moving" in the
same direction and six positions apart.

If the lamps all free ran they wouldn't stay synchronised enough to
produce the constant visual effect. Well not without spending a
relatively large amount on an accurate clock in each one.

"Accurate" meaning that they all tick at the same rate *and* all
drift by the same amount due to temperature or WHY. IIRC the step
time between lamps is 200 ms if that changed by more than 20 ms I
think it would be very noticeable. 20 ms over 24 hours is 1 part in
4.32 million. That's not easy to consistently mass produce.

It's not that difficult with the divide by 2^22 counters that take a crystal of 32,768 Hz down to 1 Hz that get you some pretty good accuracies for watches that cost less than a birthday card.

--
Cheers
Dave.

On Wed, 25 May 2016 03:24:47 -0700, whisky-dave wrote:

It's not that difficult with the divide by 2^22 counters that take a
crystal of 32,768 Hz down to 1 Hz that get you some pretty good
accuracies for watches that cost less than a birthday card.

OOI, if you want to go to the other extreme, geta watch with an atomic
clock in it! I recently visted these people:

http://goo.gl/223C5D

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On Wed, 25 May 2016 03:24:47 -0700 (PDT), whisky-dave wrote:

"Accurate" meaning that they all tick at the same rate *and* all
drift by the same amount due to temperature or WHY. IIRC the step
time between lamps is 200 ms if that changed by more than 20 ms I
think it would be very noticeable. 20 ms over 24 hours is 1 part
in
4.32 million. That's not easy to consistently mass produce.

It's not that difficult with the divide by 2^22 counters that take a
crystal of 32,768 Hz down to 1 Hz that get you some pretty good
accuracies for watches that cost less than a birthday card.

But we don't want a 1 second tick but a 200 ms one *and* happening in
sync, all the time, with all the other lamps (up to 250 IIRC) over a
temperature range of at least -10 to +30 C, though in full sun the
lamps may well get considerablly hotter inside. And with free running
clocks you still need some means of setting, to a pretty fine
tolerance, when a given lamp is to flash.

Flashing an IR light with an embeded code of some sort is far simpler
and very much more reliable compared to free running clocks.

A "birthday card" watch with an accuracy of 1 s in 24 hours (30 ish
seconds a month) is only 1 part in 86,400 not 1 in 4,320,000.

--
Cheers
Dave.

On Wednesday, 25 May 2016 17:05:14 UTC+1, Dave Liquorice wrote:
On Wed, 25 May 2016 03:24:47 -0700 (PDT), whisky-dave wrote:

"Accurate" meaning that they all tick at the same rate *and* all
drift by the same amount due to temperature or WHY. IIRC the step
time between lamps is 200 ms if that changed by more than 20 ms I
think it would be very noticeable. 20 ms over 24 hours is 1 part
in
4.32 million. That's not easy to consistently mass produce.

It's not that difficult with the divide by 2^22 counters that take a
crystal of 32,768 Hz down to 1 Hz that get you some pretty good
accuracies for watches that cost less than a birthday card.

But we don't want a 1 second tick but a 200 ms one *and* happening in
sync, all the time, with all the other lamps (up to 250 IIRC) over a
temperature range of at least -10 to +30 C, though in full sun the
lamps may well get considerablly hotter inside. And with free running
clocks you still need some means of setting, to a pretty fine
tolerance, when a given lamp is to flash.

Flashing an IR light with an embeded code of some sort is far simpler
and very much more reliable compared to free running clocks.

A "birthday card" watch with an accuracy of 1 s in 24 hours (30 ish
seconds a month) is only 1 part in 86,400 not 1 in 4,320,000.

Then pay a bit more or maybe less for a faster clock frequency.