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Forum Index : Electronics : EG8010 frequency Accuracy
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| oreo Regular Member  Joined: 11/12/2020 Location: CanadaPosts: 69 |
So I have been running an EG8010 based inverter for awhile now, and recently connected a circuit which has a clock on it. The clock was running quite fast, so I compared the frequency of the inverter to the mains and found: Mains: 59.98Hz Inverter: 60.18Hz This would suggest a crystal accuracy of 3000 PPM. Looking at the board, I can see the 2 capacitors connected to the crystal are present. I would prefer to not take the system down till the weekend, so thought I would float this question. What kind of frequency accuracy are you seeing with your EG8010 inverter? Looking on Digikey, I see crystals in the correct package with 10ppm frequency accuracy and stability. The poorest frequency accuracy crystal I see, is 100ppm.  Thoughts? Greg |
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| noneyabussiness Guru  Joined: 31/07/2017 Location: AustraliaPosts: 525 |
can I ask... does it matter, your taking .2 hz? the frequency of the grid shifts quite markedly for some (way more than that) with little difference.. maybe it would be easier to tune to device you speak of.. rather than improve the accuracy by a marginal bit on the inverter?? I think it works !! |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2374 |
I think @oreo's issue is with a synchronous motor clock or mains referenced digital clock accumulating the frequency error. The short term accuracy of the grid is usually within 0.03 Hz but over the course of a day it is corrected to average exactly 50Hz (60Hz for Canada). So clocks never need adjusting. Without external correction a crystal oscillator will always drift. It is possible to pull the frequency of a crystal down a little by adding a few pF in parallel. Experiment with values in the range 1pF to 5.6pF. Larger values than that may cause instability. Use an NPO type for temperature stability. It still won't be as good as the mains though. For that replace the crystal with a GPS disciplined precision oscillator. |
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wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1172 |
I calculated that your inverter is causing a 4.32 minutes error per 24 hours for a mains synched clock, which would annoy me also. Especially being a cumulative error. Although the mains is not dead accurate over short periods I believe their brief is to ensure there are 5184000 cycles per 24 hours in US (4320000 here) and near midnight the generating authority play a little catchup or slow down to make it so. I also calculate that the error you are seeing is the equivalent of a 36kHz error in the 12MHz oscillator, yes 100 times worse than a 30part per million initial crystal error. I believe that you can only "pull" a crystal by a few KHz with capacitors so maybe there is something else going on? I suggest bread-boarding a bare minimum EG8010 circuit with a 12MHz crystal and start with your 60Hz tweaking (monitor SPWM 1 or 2 from memory) whilst nothing else is at play and go from there. If that magnitude of error is still there it points to a possible issue with the internals of the EG8010 ASIC code? I have heard of people's digital clocks (mains synched) that gain time when their solar inverter is operating so some HF noise was maybe being seen as an extra Hz cycle from time to time, possibly waveform distortion with certain loads is tricking the clock ? In my opinion you should be able to at least identify where the issue is or/and hopefully get it a lot closer than where you are now? Edited 2025-01-25 12:09 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 525 |
or spend 10 bucks on a battery clock... no more timing issues with mains... like I asked, it seems like a unnecessary waste of time... but if you are serious, just bite the bullet and buy a 10ppm or less crystal ( if possible) and test it(start with simply replacing it on the control board)... there was a thread a few years back, a few went into the accuracy of the eg8010 and crystal combo ( maybe search here or anotherpower) and found it didn't drift all that much.. well the thread died.. also, again unsure if the oscillator would drift too, but the eg8010 has a frequency adjustment feature, you could try and set it manually and see if you get the same drift... just a thought.. I think it works !! |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 69 |
Thanks for the suggestions and comments. True, and I suppose I could ignore the microwave clock, but the coffee maker makes coffee 5 minutes earlier every day! As Mike suggested, I set up another one of these EGS002 boards on the bench, and found that the crystal (according to my scope) was running at 16.0006mHz. As Mike99 suggested, by adding 10pf (my smallest available capacitor) in parallel to both legs of the crystal, brought it down to 15.9998mHz. I removed these 2 caps and measured the 8010 output frequency, by capturing the waveform and measuring the period (storage scope). I measured 60.21376Hz. I then changed the frequency of the module to 50 hz and repeated the process and measured 50.02Hz. I can't believe it, but it appears there is a problem with the EG8010 coding when using 60Hz. If my measurements are correct, I need a 11.958Mhz crystal or crystal oscillator. Greg |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 69 |
double post Edited 2025-01-26 14:47 by oreo Greg |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 525 |
maybe try the adjustable frequency option. doesn't sound like it's the crystal accuracy after all if the 50hz is right, adjust it to 60hz or as close as and maybe it will keep it better as it will be using a different " set of code " in the chip.. I didn't mean to be rude about the point of this... its just been beaten to death in other threads.. I think it works !! |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 440 |
I also have the same problem. My pool timer uses synchronous motor and it also runs fast. I have to reset the timer after a few days. I am guessing that the EG8010 was originally designed for 50Hz and they just added an option for 60Hz but the result is not as accurate. |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 69 |
No worries, I am your typical male. I am not programmed from the factory to determine if someone is being rude or recognize if I myself am being rude. Tinyt -thanks for chiming in! I did find another thread here with complaints about 60hz stability. Since last night, I have compared my digital clock time, to my watch 3 times 1-5hr spans and got different error differences suggesting frequencies of 60.18, 60.14 and 60.23 Hz. Average frequency over the whole period is 60.17Hz. So the inverter seems to be running fast, but not consistently which does not make any sense to me. Noise would make more sense, but there is no noise when operating just the module on the bench. My inverter output waveform can look really good depending on the load. Here is it with the microwave and furnace on. This is about as bad as I have seen it get. Note that the frequency measured by the scope jumps between 59.686 and 60.686 hz (2 values).  I think I will monitor the clock error for a longer period. Greg |
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| oreo Regular Member Joined: 11/12/2020 Location: CanadaPosts: 69 |
So I finally got around to trying the variable frequency function of the 8010, which is documented quite well here Unfortunately, using variable frequency does not allow you to dial in 60hz any more accurately. So I ordered a SI5131A based oscillator board which should allow me to remove the crystal and feed in the exact frequency I like. this one Not sure if I will get around to trying this as I have decided to move away from a 8010 based solution towards an Arduino based solution. Greg |
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