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Spyros73

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  1. I started working on making my own clock, based on the SB of 1/10, but then I thought that this can not work out, because every time I switch off power (and this can easily happen during a rally, as in many cars when engine starter runs, voltage drop is significant, and plc goes off for 1-2 seconds), then the SB are not counting and my clock will stay behind. I could of course automatically syncronize my clock with the RTC every time the plc goes on, but in this case, I will finally transfer the RTC error to my clock. Should I expect any official reply from Unitronics, or I have to send an e-mail?? Thanks
  2. This is what I originally tried to do. If you see my demo software, I have used a MB (I think MB6) which comes true every time SI30 changes. And here is where the problem occurs, that even if I syncronize the RTC with a clock, after a while, you can see that the seconds have drift a little bit, so SI30 is not channging anymore syncronized with my clock. And the strange thing is that after a few minutes, it adds half a second, and then they are syncronized again, and so on. The problem is that in those competitions everything has to do with accurancy, and we have achieved such a good one (less than 0,5 sec), so that drift starts being significant.
  3. Hi all, thanks for your response. Here some comments from my side. To Flex727: This is exactly the behaviour I have also noticed. Although, the MI21 does not really changes randomly. If you notice, it has a max value e.g 8, and decreases litle by litle till to reach a min value (5 less), and then returns again to its max value. So it look to me like an internal control of the RTC, which every time sees that it has lost 5/10 of a second, it adds 5/10. In fact, in my operational software, we had realy noticed this, just by watching on the clock. We were adjusting it, according to an external watch, and now and then we could see some differences . To Ausman: Yes indeed on my operational software I am using also two conductive sensors, coupled on wheels, and connected to VFC on the plc, in order to measure the driven distance. As we are talking about regularity rallies, it's essential to compare theoretical distance (based on given average and time), with really driven distance. The sample software I downloaded, was just to show the problem I noticed. I will have a look on your post later today, If I understand well, you propose to create my own RTC, based on the SB?? Regards
  4. Oh sorry, just ignore it, I wanted to try if I can force the scantime. ( I can do this in schneider PLC) Anyway, for your info, on my normal software which is much bigger, the scan time is 4 ms
  5. Thank you both, for your reply. Monthly drift of RTC is as you say (~1 sec per day), and this is ok for me, but this is not my problem. I have attached a simple software, where you can see what I mean. I am using 3 counters. MI13 increases by 10 when SB13 is true, MI15 increases by 1 when SB15 is true. MB 19 is their difference, calculated when SB13 is true. MI19 stays constant which sound very logical. I am also using MI17 which increases by 10, every time SI30 (seconds of RTC) change, and then I also calculate the difference between, MI17 and MI15, and save it on MI21. In this case, if you follow the software for a few minutes, you will notice that the MI21 is not stable, but little by little changes, and in a certain moment, it returns to its initial value (kind of auto correction of the clock indication). Please have a look and let me have your comments For my application, is crucial to know that the time I see on the screen is really the one saved on the RTC. test clocks.vlp
  6. Hello, I am using SAMBA PLC (4.3 and 7.0 as well) for historic car rallies, in order to calculate ideal distance based on time and a given average speed. I have noticed that the RTC has a strange behaviour. I syncronize my PLC RTC with an accurate digital clock, and after a few minutes, I can notice already, a small difference (e.g. 3/10 of a second). But after a while, the two clocks are syncronized again. I tried also the following. I used the SB 15, which comes true 10 times per sec, and I increase a ML15 every time SB 15 is true. In parallel, I created a bit (MB6) which comes true, every time the RTC seconds change. Based on it, I increase ML10 by 10 this time. I compare those 2 values every second. If everything was ok, the difference of these values should always be 0, or at least something fix, but in fact I see that this difference is changing, from 0 to 5 (means max difference 0,5 sec) Why this occurs, and is there anyway to avoid it? In fact I need an accurate RTC, which will always be synchronized with the rally organization clock. Thank you in advance
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