Any engineers on board? Zero on the shot clock, no horn

[Camron Rust]

Originally Posted by pizanno

1) I start the shot clock. NCAA womens 30 sec shot clock.
2) Shot clock runs, but display still indicates 30.
3) I deduce this to mean "30" on the shot clock means 29.1 to 30.0 in actual time
OR:
"30" = 29.1 to 30.0
"29" = 28.1 to 29.0
"28" = 27.1 to 28.0
..and so on until:
"2" = 1.1 to 2.0
"1" = 0.1 to 1.0

So: how is "0" on the shot clock possible without a horn?

My brain tels me if we had zero on the shot clock, this must mean:

"0" = 0.1 to 0.9
"1" = 1.0 to 1.9
...and so on until:
"28" = 28.0 to 28.9
"29" = 29.0 to 29.9
which means:
"30" = 30.0 to 30.9 ?!!!

Does this make sense? Again, there was a delay from starting the shot clock to when the 30 changes to 29.

While I can't tell you how the specific clock you're referencing works, there are at least 3 common alternatives.

1. Truncate/Round Down...may display up to 0.99 seconds less than what really remains.
2. Round Up...may show up to 0.99 seconds more than what really remains
3. Round Closest...may show up to ~0.5 seconds more OR less than what really remains.

The last is fairly common in the mathematical and engineering world and would translate to:

• 30 => 29.5 - 30.0
• 29 => 28.5 - 29.4999...
• ...
• 1 => 0.5 - 1.4999...
• 0 => 0.0 - 0.4999...

This last option may explain the delay in the display moving upon starting AND the display of 0 without a horn.

[CMHCoachNRef]

Originally Posted by Camron Rust

While I can't tell you how the specific clock you're referencing works, there are at least 3 common alternatives.

1. Truncate/Round Down...may display up to 0.99 seconds less than what really remains.
2. Round Up...may show up to 0.99 seconds more than what really remains
3. Round Closest...may show up to ~0.5 seconds more OR less than what really remains.

The last is fairly common in the mathematical and engineering world and would translate to:

• 30 => 29.5 - 30.0
• 29 => 28.5 - 29.4999...
• ...
• 1 => 0.5 - 1.4999...
• 0 => 0.0 - 0.4999...

This last option may explain the delay in the display moving upon starting AND the display of 0 without a horn.

One other possibility here is that the game clock circuitry and operation is slightly different from the shot clock circuitry and operation. It is possible that the mechanism to reset and restart the game clock has a slight delay (not intentionally designed this way, but the way it works), while the game clock responds more quickly to the switch?

[derwil]

I'm a mechanical engineer, not electrical..........

From my understanding, during installation of the shot clock a calibration is performed of the horn vs. shot clock reading. The calibration is required due to the time lag inherant in the system: the electronic signal from the timer takes longer to get to the clock and to be displayed than it takes to go to the horn. This is due to 1. the length/type of cable used, 2. the digital to analog multi channel conversion required for the display, 3. the very quick response of horn due to the single output signal required from the timer.

Therefore, a time delta must be added to the horn function of the timer to allow the horn to sound at the same time as the display reads zero on normal play. Unfortunately, the actual timer may be stopped at a near zero situation, under the 0.1 sec mark so that the clock reads zero but if it is still inside the horn offset, the output to the horn will not be sent.

I hope this makes sense......

[Camron Rust]

Originally Posted by derwil

I'm a mechanical engineer, not electrical..........

As an electrical engineer....

Originally Posted by derwil;[COLOR=black

569554][/color]

From my understanding, during installation of the shot clock a calibration is performed of the horn vs. shot clock reading. The calibration is required due to the time lag inherant in the system: the electronic signal from the timer takes longer to get to the clock and to be displayed than it takes to go to the horn.

Nope. In most installations, the horn is integrated into scoreboard. The signal travels over the very same wire....same delay.

Originally Posted by derwil

This is due to 1. the length/type of cable used,

An electrical signal can circle the globe at the equator in about 0.2 seconds. The distances in a gym, even the largest in the word, can be covered in about 1 millisecond. Way too short for any calibration difference.

Originally Posted by derwil

2. the digital to analog multi channel conversion required for the display,

There will be no digital-to-analog conversion. The clock and every other element on the scoreboard are digital and the horn is either on or off...also a digital signal.

What does happen is that signal is split, digitally, into its various components. There may be some small delay in the system here but, again, it will be imperceptable and it will actually be uniform to the clock and the horn.

Originally Posted by derwil

3. the very quick response of horn due to the single output signal required from the timer.

The one major difference between the horn and the board is the speed of light versus the speed of sound. The light from the scoreboard makes it to the eyes of the observer in about 1 millisecond. But, the sound of the horn takes substantially longer. Sound takes about 1 second to go 1000 feet. So, the sound of the horn can take 0.1 to 0.3 seconds to reach the observer....but it will differ dramatically depending on where the observer is located. So, you can't really fire it early...particularly since you don't know that it should even be fired at all.

Originally Posted by derwil

Therefore, a time delta must be added to the horn function of the timer to allow the horn to sound at the same time as the display reads zero on normal play. Unfortunately, the actual timer may be stopped at a near zero situation, under the 0.1 sec mark so that the clock reads zero but if it is still inside the horn offset, the output to the horn will not be sent.

I hope this makes sense......

The only way the clock reads 0 without the horn sounding (short of a malfunction) is that the actual time on the clock is non zero but is below the displayable resolution of the clock.