Timeline for What refresh rate do digital stopwatches use?
Current License: CC BY-SA 4.0
19 events
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| May 14, 2021 at 7:32 | history | edited | ayane_m | CC BY-SA 4.0 |
fixed some problems with the assumptions
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| May 13, 2021 at 10:57 | answer | added | D.A.S. | timeline score: 5 | |
| May 13, 2021 at 6:20 | vote | accept | ayane_m | ||
| May 13, 2021 at 6:13 | answer | added | Lorenzo Marcantonio | timeline score: 5 | |
| May 13, 2021 at 6:01 | comment | added | Neil_UK | The display update only has to be fast enough that when you've pressed the 'stop' button, you see a stable figure within maybe 200 mS that looks 'instant' to you eye. The display timing has nothing to do with the timing resolution, which is the responsibility of the MCU and the stop button. It's easy to measure its timing to its system clock, which could be MHz. Whether anything finer than 1/1000th of a second is meaningful to a mechanical button and human thumb is another matter. | |
| May 13, 2021 at 5:00 | comment | added | Mitu Raj | Unfortunately humans can't read at that refresh rate, so it may well be displaying junk at the precision part :D | |
| May 13, 2021 at 4:11 | comment | added | DKNguyen | @jsotola And yet they're still displayed while the clock is ticking so you can't blame someone for trying to read them | |
| May 13, 2021 at 4:10 | comment | added | user57037 | If you had something that updated very fast, you could put it in the frame of a high-speed camera to help document what is going on. Of course you can count frames, too, but maybe it would be more convenient to have time displayed in the video. | |
| May 13, 2021 at 4:07 | comment | added | jsotola | @DKNguyen nothing to do with displaying elapsed time when the stop button is pressed ... illusion of seeing accurate elapsed time when the stopwatch is running ... for most people, anything more than 20 Hz refresh rate is just a blur on the least significant digits | |
| May 13, 2021 at 3:32 | review | Close votes | |||
| May 21, 2021 at 3:03 | |||||
| May 13, 2021 at 3:08 | comment | added | DKNguyen | @jsotola "Time reading" | |
| May 13, 2021 at 2:55 | comment | added | jsotola | what difference does the display refresh rate make? ... it has nothing to do with timekeeping | |
| May 13, 2021 at 2:45 | comment | added | Spehro 'speff' Pefhany | @DKNguyen Dividing by 1024 would be only 32Hz. This is kind of an interesting question. If they have an MCU they can take the number and convert it with some math. If it's a simple ASIC it might be easier to use a 32.000kHz crystal. | |
| May 13, 2021 at 2:23 | comment | added | StainlessSteelRat | And why 32.768kHz. It's divisible by 2 and if a clock is counting time, there is a significant chance there is a 32.768kHz crystal inside. | |
| May 13, 2021 at 2:20 | comment | added | user1850479 | Related question: electronics.stackexchange.com/questions/177844/… | |
| May 13, 2021 at 2:17 | comment | added | DKNguyen | Internally, they are probably using a 32.768kHz oscillator. A counter counts this to keep track of the time. Whether the counter literally keeps track of every pulse, or whether it runs through a divider first before being incremented/recorded into the counter (i.e. a divide ratio of 1024 means it is counting every 1ms.) is up to the designer. I have no idea what the refresh rate is on a reflective monochrome LCD. Presumably it's faster than an LCD monitor, but whether they bother to run it that fast is another matter. If I were them I would run it slooowww. | |
| May 13, 2021 at 2:16 | comment | added | user1850479 | Most RTCs use 32768 Hz as the internal clock frequency, so the clock resolution will typically be about 30 microseconds. Those cheap passive LCD displays have relatively slow refresh times though, so they're incapable of anything like that update rate. You'd have to look at the spec sheet or take it apart to know what any specific model uses though. | |
| May 13, 2021 at 2:15 | comment | added | Dwayne Reid | Read the manufacturer's documentation and specs. Also note that every manufacturer's models are most likely different from other units. | |
| May 13, 2021 at 2:12 | history | asked | ayane_m | CC BY-SA 4.0 |