MainsFrequency - Revision history

Bertrik Sikken: /* Introduction */

2023-08-02T11:04:00Z

Introduction

← Older revision		Revision as of 11:04, 2 August 2023
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	== Introduction ==		== Introduction ==
			Obsoleted by [[MainsFrequency2.0]]

	[[File:power_dip_peak.png\|800px\|top\|dips and peaks on the hour]]		[[File:power_dip_peak.png\|800px\|top\|dips and peaks on the hour]]

Bertrik Sikken at 14:38, 16 March 2023

2023-03-16T14:38:43Z

@@ Line 18: / Line 18: @@
 To keep the measurement circuit relatively safe, only a part of the electronics is actually connected to mains
 and the low-voltage side is isolated with an optocoupler.
 == Status ==

Bertrik Sikken: /* Status */

2023-03-16T13:16:04Z

Status

← Older revision		Revision as of 13:16, 16 March 2023
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	* [https://www.swissgrid.ch/en/home/operation/grid-data/current-data.html#frequency Swiss grid frequency graph]		* [https://www.swissgrid.ch/en/home/operation/grid-data/current-data.html#frequency Swiss grid frequency graph]
	* [http://www.mainsfrequency.com/ mains frequency]. NOTE: don't leave this site open for too long, it'll ban your IP for 'traffic exceeded' reasons!		* [http://www.mainsfrequency.com/ mains frequency]. NOTE: don't leave this site open for too long, it'll ban your IP for 'traffic exceeded' reasons!

	~~Possible future enhancements:~~
	* Display the frequency on a nice little OLED screen (or something similar)

	== Hardware ==		== Hardware ==

Bertrik Sikken: /* Reboot */

2023-03-16T11:58:31Z

Reboot

← Older revision		Revision as of 11:58, 16 March 2023
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	For measurement with an ESP8266, like a Wemos D1 mini or nodemcu, you need to put a 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.		For measurement with an ESP8266, like a Wemos D1 mini or nodemcu, you need to put a 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.
	The A0 input already has a 220k/~~100l~~ resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V range to the 0-1V range required for the ESP8266.		The A0 input already has a 220k/100k resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V range to the 0-1V range required for the ESP8266.

	The "blue pill" seems to have too low accuracy of the built-in crystal, about 100 ppm, while we need about 20 ppm to get 1 mHz resolution. Notes about blue pill crystal accuracy:		The "blue pill" seems to have too low accuracy of the built-in crystal, about 100 ppm, while we need about 20 ppm to get 1 mHz resolution. Notes about blue pill crystal accuracy:

Bertrik Sikken: /* Reboot */

2023-03-16T11:56:24Z

Reboot

← Older revision		Revision as of 11:56, 16 March 2023
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	https://github.com/bertrik/MainsFrequency		https://github.com/bertrik/MainsFrequency

	For measurement with an ESP8266, like a Wemos or nodemcu, you need to put ~~about~~ 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.		For measurement with an ESP8266, like a Wemos D1 mini or nodemcu, you need to put a 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.
	The A0 input already has a 220k/100l resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V range to the 0-1V range required for the ESP8266.		The A0 input already has a 220k/100l resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V range to the 0-1V range required for the ESP8266.

Bertrik Sikken: /* References */

2023-03-16T09:41:19Z

References

← Older revision		Revision as of 09:41, 16 March 2023
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	Other interesting projects/documents:		Other interesting projects/documents:
	* https://oinkzwurgl.org/projaeggd/mains-frequency/		* https://oinkzwurgl.org/projaeggd/mains-frequency/
	* http://www.palebluedot.nl/jml/projects/arduino/43-measure-mains-power-frequency		* <s>http://www.palebluedot.nl/jml/projects/arduino/43-measure-mains-power-frequency</s>
	* https://engmousaalkaabi.blogspot.nl/2016/11/ac-220v-frequency-counter-using-arduino.html		* <s>https://engmousaalkaabi.blogspot.nl/2016/11/ac-220v-frequency-counter-using-arduino.html</s>
	* Interesting [http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf App Note by Microchip] about capacitive droppers		* Interesting [http://ww1.microchip.com/downloads/en/AppNotes/00954A.pdf App Note by Microchip] about capacitive droppers
	* https://a01.veron.nl/download/hamnieuws/2016/Ham-06-2016.pdf (see page 20, 220nf, 2M Ohm bleeder)		* https://a01.veron.nl/download/hamnieuws/2016/Ham-06-2016.pdf (see page 20, 220nf, 2M Ohm bleeder)

Bertrik Sikken: /* Reboot */

2023-03-16T09:25:25Z

Reboot

← Older revision		Revision as of 09:25, 16 March 2023
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	For measurement with an ESP8266, like a Wemos or nodemcu, you need to put about 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.		For measurement with an ESP8266, like a Wemos or nodemcu, you need to put about 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.
	The A0 input already has a 220k/100l resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V ~~down~~ to the 0-1V range required for the ESP8266.		The A0 input already has a 220k/100l resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V range to the 0-1V range required for the ESP8266.

	The "blue pill" seems to have too low accuracy of the built-in crystal, about 100 ppm, while we need about 20 ppm to get 1 mHz resolution. Notes about blue pill crystal accuracy:		The "blue pill" seems to have too low accuracy of the built-in crystal, about 100 ppm, while we need about 20 ppm to get 1 mHz resolution. Notes about blue pill crystal accuracy:

Bertrik Sikken: /* Reboot */

2023-03-15T22:33:31Z

Reboot

← Older revision		Revision as of 22:33, 15 March 2023
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	Proposed algorithm for getting accurate instantaneous frequency out of it:		Proposed algorithm for getting accurate instantaneous frequency out of it:
	* Sample the mains frequency waveform ~~at 10 kHz (400 samples per mains cycle nominally)~~ during approximately one second		* Sample the mains frequency waveform during approximately one second (say 5 - 10 kHz)
	* Determine the median, lower and upper quartiles of the waveform, and shift data so its values are symmetrically around zero		* Determine the median, lower and upper quartiles of the waveform, and shift data so its values are symmetrically around zero
	* Calculate zero crossings by doing linear regression to find the zero-crossing of the wave in the region around the zero crossing (in between the quartile values), this gives sub-sample time resolution		* Calculate zero crossings by doing linear regression to find the zero-crossing of the wave in the region around the zero crossing (in between the quartile values), this gives sub-sample time resolution
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	* Do this over the approximately 50 cycles contained in the one second data and determine average frequency		* Do this over the approximately 50 cycles contained in the one second data and determine average frequency
	-> this should give about 1 millihertz frequency resolution in one second		-> this should give about 1 millihertz frequency resolution in one second

	~~Implementation I intend to use:~~
	* an STM32 ("blue pill") does the analog stuff, sampling the mains frequency wave form
	* an ESP8266 handles communication over WiFi, controls the STM32
	* the STM32 and the ESP8266 communicate over a simple serial line, 3V, TTL, perhaps even simple ASCII so it can be debugged easily during development
	* the STM32 samples in a "simple" data capture mode, using a timer driven with crystal accuracy, one interrupt per sample
	* the STM32 runs the interpolation algoritm, calculate things to 1 microsecond resolution

	Github project:		Github project:
	https://github.com/bertrik/MainsFrequency		https://github.com/bertrik/MainsFrequency

	Notes about blue pill crystal accuracy:		For measurement with an ESP8266, like a Wemos or nodemcu, you need to put about 180k ohm resistor in line with the output from the ZMPT101B to the A0 input.
			The A0 input already has a 220k/100l resistive divider, effectively becoming a 400k/100k resistive divider with the series resistor, scaling down the 0-5V down to the 0-1V range required for the ESP8266.

			The "blue pill" seems to have too low accuracy of the built-in crystal, about 100 ppm, while we need about 20 ppm to get 1 mHz resolution. Notes about blue pill crystal accuracy:
	https://sparklogic.ru/arduino-for-stm32/accurate-blue-pill-clock-frequency-adjustment.html		https://sparklogic.ru/arduino-for-stm32/accurate-blue-pill-clock-frequency-adjustment.html

Bertrik Sikken: /* Reboot */

2023-01-08T20:19:12Z

Reboot

← Older revision		Revision as of 20:19, 8 January 2023
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	Github project:		Github project:
	https://github.com/bertrik/MainsFrequency		https://github.com/bertrik/MainsFrequency

			Notes about blue pill crystal accuracy:
			https://sparklogic.ru/arduino-for-stm32/accurate-blue-pill-clock-frequency-adjustment.html

	== Status ==		== Status ==

Bertrik Sikken: /* Reboot */

2023-01-08T13:36:41Z

Reboot

← Older revision		Revision as of 13:36, 8 January 2023
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	* the STM32 samples in a "simple" data capture mode, using a timer driven with crystal accuracy, one interrupt per sample		* the STM32 samples in a "simple" data capture mode, using a timer driven with crystal accuracy, one interrupt per sample
	* the STM32 runs the interpolation algoritm, calculate things to 1 microsecond resolution		* the STM32 runs the interpolation algoritm, calculate things to 1 microsecond resolution

			Github project:
			https://github.com/bertrik/MainsFrequency

	== Status ==		== Status ==