Wanted: A Very Accurate Timer

Hard to take a show seriously where spacecraft make banking turns in space and go "Whoosh" as they pass you. "Blake's 7" at least got that part right.

N

I've a radio-controlled clock and a nominally-50Hz-driven one in the same room. There's only any point in synchronising them early in the morning: that way, they'll agree again every morning, i.e. the 50HZ is carefully kept to be *on average* true, but by evening, especially in winter, the difference can be as much as 20 seconds.

Nor can I ...

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Peter Duck

Thanks for all the responses.

I originally entertained something like this 2-1/2 years ago, but the timer I needed, which was basically a racing watch, but with a large bright red display, was not commercially available and proved too complicated to build.

So I have to settle on just a simple timer for now, and worry about getting something more complex later.

It is way too complicated to go into the details as far as why I need this, but basically this will involve conducting experiments/tests on the accuracy of human timing, and also the confirmation of certain conclusions drawn from studying the code contained within the hardware I'll be testing against.

1/60th of a second is important because it is specific to that hardware and how it functions. It uses registers that change every 1/60th of a second to make certain occurances "random". If one could react with an accuracy of 1/60th of a second, then these occurances would follow a predictable pattern. But of course that kind of timing is not humanly possible with any kind of consistency.

Anyway, to simplify what I'm doing, this involves a huge number of timed inputs(by a person) over the course of several hours. The timer will be the reference.

If it is easier for me to get a set-up that involves frequent resets/corrections to get the needed accuracy at any 60th of a second over the course of several hours, then that is what I'll have to do.

P.S: The hardware itself is a videogame.

Darren Harris Staten Island, New York.

This strikes me as a very different definition of the problem from your original post...

If your goal is to have an event 60 times per second with good accuracy, that is trivial with most microcontrollers. Even a basic design could get you 100,000 events per second with good accuracy.

But what you described in your original post was a requirement to finish after 6 hours with a clock drift of no more than 1/60 second. That problem is 21,600 times harder, and requires elaborate solutions.

i.e., it sounds like your requirement is for a timer that can: a) trigger 60 times per second with "good" accuracy b) count for 6 hours or more

In defining "good" accuracy, 1% equates to +/- 0.00017 secs margin per

60/sec event (between 0.01649 and 0.01683 seconds per event). These timings aren't likely to vary much on one board (barring temerature changes), but would vary in this range from one board to the next.

So, what degree of accuracy are you really needing?

Cheers, Richard

How? In my original post I said the following: "It must to be accurate to within 1/60th of a second over the course of 6 hours."

But that is not my goal.

Still wrong. The timer will trigger nothing. All it needs is a display so that I can see the seconds.(Though showing 1/60th of a second intervals would be great, it's just not required for this project, which I have had to simplify greatly).

1/60th of a second...

(ie: When the 2 hour, 53 minute, and 37 second point is reached, the display should show it at exactly that time at an accuracy of 1/60th of a second from when the clock started running).

Darren Harris Staten Island, New York.

[...]

You have no idea what your requirements mean. A drift of 1ppm in 6 hrs is meaningless in a marathon or other race, when the wind can easily cause

1% change in performance.

So in Brooklanese -Fahgettaboutit!

Mike Monett

There is no wind involved here.

I've been trying not to get into the details, because details lead to the request for more details, and this is just way to complex to get into here. Not just as far as what I'm doing, but the timer I am seeking is actually inadequate for all of the experiments I want to do.

Now if this is so difficult to understand, then the more complex timer will be near impossible to explain.

For this project there will be 1,296,000 increments over the course of

6 hours. I just need the option of *visually* seeing on the timer's display when each second increments beginning with the press of a start button, and the accuracy must be 1/60th of a second at worst for any of those 21,600 seconds after zero.(I'm assuming that the timer will have to be plugged in an AC outlet).

Darren Harris Staten Island, New York.

[...]

I think you just lost the interest of anyone capable of helping you.

The truth you seek is out there. Have fun:)

Mike Monett

Have a think about it and perhaps that will simplify your problem

David

Well compensating for centrifugal force is plausible, and space is not a complete vacuum. :-)

Darren Harris Staten Island, New York.

No. I'm sure that accuracy is definitely what is needed.

The problem is what it is. There is nothing that can be changed.

Obviously, even this simple version of a timer is not commercially available, and not something that can be easily built.

Thanks.

Darren Harris Staten Island, New York.

Oops, I'm off by one decimal place; it's more like one part in 1.3 million. This can be done with a good crystal oscillator, but it's got to be a pretty good one, and it has to be calibrated against a real standard.

The question remains of why one would need this degree of accuracy in a timing function.

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----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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...

You will waste a lot less of everyone's time if you just go ahead and explain what you want. If you happen to know. Of course if you don't know what you want, you are less likely to get it.

Anyhow, AIUI you have a video game and you want to use a timer for doing something related to this game ... perhaps you want to reverse engineer it, perhaps crack some protection, perhaps set up a computer- aided play device. Whatever. And you think that having a timer with

1/60 second accuracy displaying the current time throughout a six hour period will help you do so. (It may be silly for you to think so, because if you are just reading the time off the running display or pushing buttons to record the time when stuff happens, you won't be able to do either one with 1/60 second reaction times anyway.)

Note that the clock in the video game almost certainly will drift around in a range at least 10 parts per million wide, which makes your 1 ppm requirement superfluous. Instead, snoop the video game clock and use a buffered copy of it to drive the counters in your timer. This way your displayed time always is in sync with the video game time.

Perhaps your problem is that you don't know what you are doing. Feel free to convince us otherwise.

As several people have noted, you could use a TXCO (temperature compensated crystal oscillator) or a crystal oven for adequate performance. See eg $4 and $18 items

Note that you can get an inexpensive counter/timer on ebay, like

The bench instruments probably have 7 to 10 digit stability when warmed up and similar accuracy when in cal. Some of them might make their timebases externally available and/or have totalizer functions that would do the job for you. In any case, if you build a TXCO you'll need a counter/timer to check it.

-jiw

Darren,

You are correct that it takes details to provide a useful answer. Based on the broad question originally asked, the URL I provided should have met your needs. Perhaps if we understood why you didn't find what you needed there, more accurate responses might be possible.

If you work with engineers much, you'll appreciate that people very often ask for the wrong thing - by challenging questionable requirements the true specs become known, often hugely affecting the complexity involved. Here, you are asking for a degree of accuracy that is difficult to achieve, but you say you won't actually be using it, which sounds flawed. (Irrespective of the event frequency in the DUT, if you are only capturing one-second granularity, more accuracy is wasted.)

So, you're wasting everyone's time (including yours) looking for a solution that won't meet your needs? If you really want nanosecond accuracy, we can guide you to a solution that'd give you that, but not if you don't ask.

If you would be less defensive about the requirements and share more about your desired goal, you might get help in meeting it - the volume of responses here demonstrates folks' willingness to help. We don't need you to divulge your experiment, but significant requirements would be nice (budget, size, weight, power, connectivity, inputs, outputs, skillset), along with some tolerance for validating the potentially difficult specs.

All that said, have you considered the overly simple solution of software on a PC? It may be difficult to get better than 18.2ms resolution from the system clock, but that is very close to your stated requirement, and an RTC clock card would be easy enough to add.

Then, use SNTP to frequently check an atomic source and factor the drift into the local clock's readings. (Or ditch the local clock entirely and just make an SNTP/Daytime query of an atomic clock at the time you want a reading - the accuracy can be calc'd as good as 1/250 sec.) Plus, this is easily extensible to integrate with an event log, rather than using a manual process.

Of course, there's no knowing if this will meet your other unstated requirements, so perhaps it was a waste of time to share this idea?

Richard

If, even with expert help, a problem appears to be hard or expensive to solve, change the problem. Every engineer has done that at least one but probably several times...

--
Met vriendelijke groet,

   Maarten Bakker.

I said in my very first post that I was looking for an electronic timer that is accurate to within 1/60th of a second over the course of 6 hours. Then the thread turned into questions concerning my project and assumptions as to why what I ask for wasn't logical.

I did previously say: "But of course that kind of timing is not humanly

possible with any kind of consistency."

I'm aware of the consistency of the game hardware. And this project can't involve tapping into the games clock.

The problem is the criticizing of my needs and the suggestion of alternatives by those unfamiliar with the project. The initial question was simple, and I thank those who gave me their best answers.

I'm just looking for a timer to click off every second on it's display, and with the accuracy I mentioned. I know nothing about how to build anything, or about the features of the devices in those links.

Darren Harris Staten Island, New York.

I'm not asking for the wrong thing. The requirements are only "questionable to someone not familiar to with what I am trying to do. I never said that I will not be using the accuracy I am searching for. And I think it has already been established that the kind of accurate timer I need doesn't exist(or no one here knows of one).

Who said that I'm looking for a solution that won't meet my needs?(And I only need 1/60th of a second acccuracy).

All this is unecessary info for a timer with a simple read-out. There are no other rquirements than what I stated.

Again, I need only 1/60th of a second accuracy, and the reference point will be from "start".

Yeah. I guess I'll have to look elsewhere.

Thanks.

Darren Harris Staten Island, New York.

The problem is getting a timer.

Darren Harris Staten Island, New York.

I've already simplified the timer requirements so as to target part of my "problem".

Darren Harris Staten Island, New York.