MHZ19 - Revision history

Disasm: Add link to MH-Z19B

2019-10-01T22:52:58Z

Add link to MH-Z19B

← Older revision		Revision as of 22:52, 1 October 2019
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	See also [https://geektimes.ru/post/285572/ this page on geektimes.ru] that explains some of the mysteries around this sensor that I didn't figure out.		See also [https://geektimes.ru/post/285572/ this page on geektimes.ru] that explains some of the mysteries around this sensor that I didn't figure out.
	</b>		</b>

			See also: [[MH-Z19B]]

	== Status ==		== Status ==

Bertrik Sikken: /* Hardware and reference data */

2018-07-05T23:29:13Z

Hardware and reference data

← Older revision		Revision as of 23:29, 5 July 2018
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	== Hardware and reference data ==		== Hardware and reference data ==
	See [http://www.winsen-sensor.com/products/ndir-co2-sensor/mh-z19.html the manufacturer MH-Z19 page].		See [http://www.winsen-sensor.com/products/ndir-co2-sensor/mh-z19.html the manufacturer MH-Z19 page].

			[https://forum.mysensors.org/topic/7761/mh-z19-teardown/2 Here's a teardown] of the MH-Z19 showing what it actually looks like inside.
			Basically a light source and curved mirror focusing the light onto a photo diode with an optical filter tuned to a CO2 peak.
			It has an STM32F103 processor inside, the same kind as the one on the famous 'blue pill' board.

	== Software ==		== Software ==

Bertrik Sikken: Completed

2017-05-09T07:57:00Z

Completed

← Older revision		Revision as of 07:57, 9 May 2017
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	\|Picture=mhz19.jpg		\|Picture=mhz19.jpg
	\|Omschrijving=Some research into the MH-Z19 CO<sub>2</sub> sensor		\|Omschrijving=Some research into the MH-Z19 CO<sub>2</sub> sensor
	\|Status=~~In progress~~		\|Status=Completed
	\|Contact=bertrik		\|Contact=bertrik
	}}		}}

Bertrik Sikken: Add connection between Wemos and MHZ19

2017-04-14T05:46:40Z

Add connection between Wemos and MHZ19

← Older revision		Revision as of 05:46, 14 April 2017
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	See [https://github.com/bertrik/mhz19 this github repo] for code using this sensor with an ESP8266 board (WeMos D1 mini).		See [https://github.com/bertrik/mhz19 this github repo] for code using this sensor with an ESP8266 board (WeMos D1 mini).
	It publishes the CO<sub>2</sub> concentration to a MQTT topic every 5 seconds.		It publishes the CO<sub>2</sub> concentration to a MQTT topic every 5 seconds.

			To connect the Wemos to the MHZ19:
			* GND to both the Wemos and MHZ19 GND pin
			* 5V to the Wemos +5V pin and MHZ19 Vin pin
			* Wemos D1 pin to the MHZ19 TX pin
			* Wemos D2 pin to the MHZ19 RX pin

	It seems that support for this sensor was recently added to [https://www.esp8266.nu/index.php/ESPEasy ESPEasy].		It seems that support for this sensor was recently added to [https://www.esp8266.nu/index.php/ESPEasy ESPEasy].

Bertrik Sikken at 20:41, 19 March 2017

2017-03-19T20:41:35Z

← Older revision		Revision as of 20:41, 19 March 2017
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	The sensor works as intended, some software has been written to read the CO2 level and publish measurements it on MQTT.		The sensor works as intended, some software has been written to read the CO2 level and publish measurements it on MQTT.
	It is also clear how to change the measurement range from 0-2000ppm to 0-5000ppm in software.		It is also clear how to change the measurement range from 0-2000ppm to 0-5000ppm in software.

			Currently, it's running in Space3, publishing its value on a topic on MQTT, you can read this as follows:
			mosquitto_sub -h revspace.nl -t revspace/sensors/co2/# -v

	See also https://revgraph.bewaar.me/dashboard/db/all-co2		See also https://revgraph.bewaar.me/dashboard/db/all-co2
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	== Software ==		== Software ==
	See [https://github.com/bertrik/mhz19 this github repo] for code using this sensor with an ESP8266 board (WeMos D1 mini).		See [https://github.com/bertrik/mhz19 this github repo] for code using this sensor with an ESP8266 board (WeMos D1 mini).
	It publishes the CO<sub>2</sub> concentration to topic ~~"bertrik/co2" on test.mosquitto.org~~ every 5 seconds.		It publishes the CO<sub>2</sub> concentration to a MQTT topic every 5 seconds.

	It seems that support for this sensor was recently added to [https://www.esp8266.nu/index.php/ESPEasy ESPEasy].		It seems that support for this sensor was recently added to [https://www.esp8266.nu/index.php/ESPEasy ESPEasy].

Bertrik Sikken at 11:24, 18 March 2017

2017-03-18T11:24:20Z

← Older revision		Revision as of 11:24, 18 March 2017
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	9F 83 07 7D 00 00		9F 83 07 7D 00 00
	</pre>		</pre>
	The value 0x9F83 looks similar to the output of command 0x84.		The value 0x9F83 (40835 in decimal) looks similar to the output of command 0x84.

	The value 0x077d looks similar to the output of command 0x85.		The value 0x077d (1917 in decimal) looks similar to the output of command 0x85.

	=== command 0x71, 0x72 ===		=== command 0x71, 0x72 ===
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	=== command 0x73 ===		=== command 0x73 ===
	<pre>9F 86 00 00 3D 40</pre>		<pre>9F 86 00 00 3D 40</pre>
	0x9F86 looks similar to output of command 0x84.		0x9F86 = 40838 decimal, looks similar to output of command 0x84.
	0x3d40 = 15680 decimal.		0x3d40 = 15680 decimal.

	<pre>07 8C 00 00 3D 04</pre>		<pre>07 8C 00 00 3D 04</pre>
			* 0x078c = 1932 decimal
	* the 0x3D is temperature I think		* the 0x3D is temperature I think
	* the 0x04 is the 'status' byte		* the 0x04 is the 'status' byte
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	Some other time		Some other time
	<pre>9F A1 00 80 00 00</pre>		<pre>9F A1 00 80 00 00</pre>
	=== command 0x85 ===
			=== command 0x85 (read CO2 + alarm level?) ===
	This command gives a response as follows:		This command gives a response as follows:
	<pre>		<pre>

Bertrik Sikken at 22:42, 17 March 2017

2017-03-17T22:42:21Z

← Older revision		Revision as of 22:42, 17 March 2017
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	The sensor works as intended, some software has been written to read the CO2 level and publish measurements it on MQTT.		The sensor works as intended, some software has been written to read the CO2 level and publish measurements it on MQTT.
	It is also clear how to change the measurement range from 0-2000ppm to 0-5000ppm in software.		It is also clear how to change the measurement range from 0-2000ppm to 0-5000ppm in software.

			See also https://revgraph.bewaar.me/dashboard/db/all-co2

	Next steps:		Next steps:

Bertrik Sikken at 09:31, 11 March 2017

2017-03-11T09:31:09Z

← Older revision		Revision as of 09:31, 11 March 2017
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	=== command 0x62 (device name / id) ===		=== command 0x62 (device name / id) ===
			According to the information at https://geektimes.ru/post/285572/
			this command should return a kind of string, I couldn't get this to work unfortunately
	<s>		<s>
	Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS" ~~(from https://geektimes.ru/post/285572/)~~		Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS"
	</s>		</s>

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	* SS is some kind of status byte, this byte always has only one bit set!		* SS is some kind of status byte, this byte always has only one bit set!
	* Uh/Ul is some unknown value, perhaps related to pressure? After booting the sensor, it starts out at 15000 exactly, then typically settles to about 10500.		* Uh/Ul is some unknown value, perhaps related to pressure? After booting the sensor, it starts out at 15000 exactly, then typically settles to about 10500.
	According to the geektimes.ru page, this value is related to the minimum CO2 uncorrected concentration measured in the past day. So I guess this is a relevant parameter from the ABC-algorithm.		According to the geektimes.ru page, this unknown value is related to the minimum CO2 uncorrected concentration measured in the past day. So I guess this is a relevant parameter from the ABC-algorithm.
	* Cs is the checksum		* Cs is the checksum

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	<pre>		<pre>
	HH LL TT SS U1 U2		HH LL TT SS U1 U2
	RAW: 00 80 47 01 3A 98		RAW: 00 80 47 01 3A 98 -> CO2 = 128 ppm
	RAW: 07 D0 47 01 3A 98 -> 0x7d0 = 2000 decimal, this is the configured measurement range of the sensor with command 0x99		RAW: 07 D0 47 01 3A 98 -> 0x7d0 = 2000 decimal, this is the configured measurement range of the sensor with command 0x99
	RAW: 00 05 47 01 3A 98		RAW: 00 05 47 01 3A 98 -> CO2 = 5 ppm
	RAW: 01 2D 47 01 3A 98		RAW: 01 2D 47 01 3A 98 -> CO2 = ..
	RAW: 28 97 47 01 3A 98		RAW: 28 97 47 01 3A 98 -> CO2 = 10391
	RAW: 28 97 47 01 3A 98		RAW: 28 97 47 01 3A 98
	RAW: 28 97 47 01 3A 98		RAW: 28 97 47 01 3A 98

Bertrik Sikken at 17:29, 10 March 2017

2017-03-10T17:29:22Z

← Older revision		Revision as of 17:29, 10 March 2017
Line 73:		Line 73:

	=== command 0x62 (device name / id) ===		=== command 0x62 (device name / id) ===
			<s>
	Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS" (from https://geektimes.ru/post/285572/)		Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS" (from https://geektimes.ru/post/285572/)
			</s>

	=== command 0x70 ===		=== command 0x70 ===

Bertrik Sikken at 17:14, 10 March 2017

2017-03-10T17:14:14Z

← Older revision		Revision as of 17:14, 10 March 2017
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	Untested.		Untested.

			=== command 0x62 (device name / id) ===
	Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS" (from https://geektimes.ru/post/285572/)		Command 0x62 seems to query the sensor for a device name, either "KB200" or "MODBUS" (from https://geektimes.ru/post/285572/)