MH-Z19B - Revision history

Juerd at 00:05, 20 January 2021

2021-01-20T00:05:50Z

← Older revision		Revision as of 00:05, 20 January 2021
Line 11:		Line 11:
	MH-Z19B is an updated version of the [[MHZ19\|MH-Z19]] sensor.		MH-Z19B is an updated version of the [[MHZ19\|MH-Z19]] sensor.

	Datasheet: https://www.winsen-sensor.com/d/files/~~infrared~~-~~gas-sensor/mh-z19b-co2-ver1_0~~.pdf		Datasheet: https://www.winsen-sensor.com/d/files/MH-Z19B.pdf

	== Hardware ==		== Hardware ==

Juerd: /* Fake MH-Z19B (black PCB) */

2021-01-20T00:05:20Z

Fake MH-Z19B (black PCB)

← Older revision		Revision as of 00:05, 20 January 2021
Line 180:		Line 180:
	* Black sealant between case and pcb, instead of clear.		* Black sealant between case and pcb, instead of clear.

	They report a sensing capacity of 10000 PPM (as the PPM output at the very first stage of starting up). According to the Winsen MH-Z19B datasheet, only 2000 and 5000 PPM models exist.		They report a sensing capacity of 10000 PPM (as the PPM output at the very first stage of starting up). <del>According to the Winsen MH-Z19B datasheet, only 2000 and 5000 PPM models exist.</del> ''(This was based on version 1.0 of the datasheet. Version 1.5 does list a 10000 PPM model.)''

	The sensors may be suitable depending on what you use them for, but they show severe jitter of up to 50 PPM (peak to peak) and they often don't properly do the ABC. My theory is that they don't ABC correctly because it won't find a suitable baseline with all those big deviations going on all the time. Not even smoothing with a 10 minute moving average gets you close to the much more steady results of the original MH-Z19B.		The fake sensors may be suitable depending on what you use them for, but they show severe jitter of up to 50 PPM (peak to peak) and they often don't properly do the ABC. My theory is that they don't ABC correctly because it won't find a suitable baseline with all those big deviations going on all the time. Not even smoothing with a 10 minute moving average gets you close to the much more steady results of the original MH-Z19B.

	The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.		The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.

	Addendum 2020-12-29: received a message from someone who has had the same experience with the black pcb fake MH-Z19B, and they made a video with some measurements: https://www.youtube.com/watch?v=5_QQe75-SZI		Addendum 2020-12-29: received a message from someone who has had the same experience with the black pcb fake MH-Z19B, and they made a video with some measurements: https://www.youtube.com/watch?v=5_QQe75-SZI

Juerd: /* Fake MH-Z19B (black PCB) */

2020-12-29T22:55:18Z

Fake MH-Z19B (black PCB)

← Older revision		Revision as of 22:55, 29 December 2020
Line 185:		Line 185:

	The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.		The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.

			Addendum 2020-12-29: received a message from someone who has had the same experience with the black pcb fake MH-Z19B, and they made a video with some measurements: https://www.youtube.com/watch?v=5_QQe75-SZI

Juerd: /* Fake MH-Z19B (black PCB) */

2020-11-30T03:26:48Z

Fake MH-Z19B (black PCB)

← Older revision		Revision as of 03:26, 30 November 2020
Line 182:		Line 182:
	They report a sensing capacity of 10000 PPM (as the PPM output at the very first stage of starting up). According to the Winsen MH-Z19B datasheet, only 2000 and 5000 PPM models exist.		They report a sensing capacity of 10000 PPM (as the PPM output at the very first stage of starting up). According to the Winsen MH-Z19B datasheet, only 2000 and 5000 PPM models exist.

	The sensors may be suitable depending on what you use them for, but they show severe jitter of up to 50 PPM (peak to peak) and they often don't properly do the ABC. My theory is that they don't ABC correctly because it won't find a suitable baseline with all big deviations going on all the time. Not even smoothing with a 10 minute moving average gets you close to the much more steady results of the original MH-Z19B.		The sensors may be suitable depending on what you use them for, but they show severe jitter of up to 50 PPM (peak to peak) and they often don't properly do the ABC. My theory is that they don't ABC correctly because it won't find a suitable baseline with all those big deviations going on all the time. Not even smoothing with a 10 minute moving average gets you close to the much more steady results of the original MH-Z19B.

	The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.		The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.

Juerd at 03:20, 30 November 2020

2020-11-30T03:20:47Z

← Older revision		Revision as of 03:20, 30 November 2020
Line 154:		Line 154:
	\| 0xAC \|\| b[3] \|\| r[2], r[3..6] \|\| ???		\| 0xAC \|\| b[3] \|\| r[2], r[3..6] \|\| ???
	\|}		\|}

			== Fake MH-Z19B (black PCB) ==

			(Added by [[User:Juerd\|Juerd]] ([[User talk:Juerd\|talk]]) 04:20, 30 November 2020 (CET))

			There are sensors out there, sold as MH-Z19B, that seem to use the original firmware, but with different hardware.

			[[Image:Fake-mhz19.png]]

			The hardware differs with the original MH-Z19B in the following ways:
			* Case:
			** No circular bump over the lamp (a faint impression can be seen under an angle)
			** No raised edges around the square "windows"
			** Slightly more yellowish gold color
			* PCB:
			** Black instead of green. This is the most recognizable difference.
			** Silkscreen differs
			*** "RoHS" is missing
			*** Pins are labeled differently: Hd/Txd/Rxd/V-/V+ instead of HD/Tx/Rx/GND/Vin
			** SWD pads have no holes
			** The pads in the top left corner are much larger
			** Vias are in completely different locations
			** The 3×3 grid of thermal vias under the MCU is missing
			** Wider neck between pin holes and connector tab
			* Black sealant between case and pcb, instead of clear.

			They report a sensing capacity of 10000 PPM (as the PPM output at the very first stage of starting up). According to the Winsen MH-Z19B datasheet, only 2000 and 5000 PPM models exist.

			The sensors may be suitable depending on what you use them for, but they show severe jitter of up to 50 PPM (peak to peak) and they often don't properly do the ABC. My theory is that they don't ABC correctly because it won't find a suitable baseline with all big deviations going on all the time. Not even smoothing with a 10 minute moving average gets you close to the much more steady results of the original MH-Z19B.

			The firmware reports version 0436 in response to the 0xA0 command. During initialization, the magic value that is 410 PPM (at least in two green pcb MH-Z19B's that look very much like the real thing, with firmware versions 0430 and 0443) and is used for filtering in [https://github.com/WifWaf/MH-Z19 this library], is not 410, but 436. Apart from that, all communication looks normal.

Disasm at 22:53, 1 October 2019

2019-10-01T22:53:28Z

← Older revision		Revision as of 22:53, 1 October 2019
Line 3:		Line 3:
	\|Picture=mhz19.jpg		\|Picture=mhz19.jpg
	\|Omschrijving=Some research into the MH-Z19B CO<sub>2</sub> sensor		\|Omschrijving=Some research into the MH-Z19B CO<sub>2</sub> sensor
	\|Status=~~Initializing~~		\|Status=Completed
	\|Contact=Disasm		\|Contact=Disasm
	}}		}}

Disasm: /* Protocol (operation mode 0) */

2019-10-01T22:51:44Z

Protocol (operation mode 0)

← Older revision		Revision as of 22:51, 1 October 2019
Line 111:		Line 111:
	b[6..7] is minimum light ADC value		b[6..7] is minimum light ADC value
	\|-		\|-
	\| 0x86 \|\| \|\| r[2..3], r[4], r[5], r[6], r[7] \|\| r[2..3] - "final" CO2 level. r[6] and r[7] - if ABC turned on - counter in "ticks" within a calibration cycle and the number of performed calibration cycles.		\| 0x86 \|\| \|\| r[2..3], r[4], r[5], r[6], r[7] \|\| r[2..3] - "final" CO2 level. r[4] - (temperature in C) + 40
			r[6] and r[7] - if ABC turned on - counter in "ticks" within a calibration cycle and the number of performed calibration cycles.
	\|-		\|-
	\| 0x87 \|\| b[5], b[6], b[7] \|\| r[2], r[3..6] \|\| ???		\| 0x87 \|\| b[5], b[6], b[7] \|\| r[2], r[3..6] \|\| ???

Disasm: /* Protocol (operation mode 0) */

2019-10-01T22:49:29Z

Protocol (operation mode 0)

← Older revision		Revision as of 22:49, 1 October 2019
Line 119:		Line 119:
	\| 0x8D \|\| \|\| no response \|\| MCU reset		\| 0x8D \|\| \|\| no response \|\| MCU reset
	\|-		\|-
	\| 0x90..0x93 \|\| b[3] \|\| r[2..5] \|\| ~~reads~~ a double word from configuration area by offset (b[3] + (CMD - 0x90) * 256)		\| 0x90..0x93 \|\| b[3] \|\| r[2..5] \|\| Reads a double word from configuration area by offset (b[3] + (CMD - 0x90) * 256)
	\|-		\|-
	\| 0x94 \|\| b[3], b[4..6] \|\| r[2..6] \|\| ~~changes~~ 3 bytes (b[4..6]) of "id string" with offset (3*(b[3] - 1))		\| 0x94 \|\| b[3], b[4..6] \|\| r[2..6] \|\| Changes 3 bytes (b[4..6]) of "id string" with offset (3*(b[3] - 1))
	\|-		\|-
	\| 0x95 \|\| b[3] \|\| r[2], r[3], r[4..6] \|\| ~~reads~~ 3 bytes of "id string" (b[4..6]) with offset		\| 0x95 \|\| b[3] \|\| r[2], r[3], r[4..6] \|\| Reads 3 bytes of "id string" (b[4..6]) with offset
	\|-		\|-
	\| 0x99 \|\| b[4..7] \|\| ACK \|\| Sets sensor range. Note that parameter bytes differ from those in the datasheet.		\| 0x99 \|\| b[4..7] \|\| ACK \|\| Sets sensor range. Note that parameter bytes differ from those in the datasheet.
Line 129:		Line 129:
	\| 0x9A \|\| b[4] \|\| ACK \|\| ???		\| 0x9A \|\| b[4] \|\| ACK \|\| ???
	\|-		\|-
	\| 0x9B \|\| \|\| r[2..5], r[6], r[7] \|\| r[2..5] ~~- sensor range~~		\| 0x9B \|\| \|\| r[2..5], r[6], r[7] \|\| Returns sensor range (r[2..5])
	\|-		\|-
	\| 0x9C \|\| \|\| r[2..5], r[6]=1 \|\| ???		\| 0x9C \|\| \|\| r[2..5], r[6]=1 \|\| ???

Disasm: /* Protocol (operation mode 0) */

2019-10-01T22:45:42Z

Protocol (operation mode 0)

← Older revision		Revision as of 22:45, 1 October 2019
Line 125:		Line 125:
	\| 0x95 \|\| b[3] \|\| r[2], r[3], r[4..6] \|\| reads 3 bytes of "id string" (b[4..6]) with offset		\| 0x95 \|\| b[3] \|\| r[2], r[3], r[4..6] \|\| reads 3 bytes of "id string" (b[4..6]) with offset
	\|-		\|-
	\| 0x99 \|\| b[4..7] \|\| ACK \|\| Sets sensor range		\| 0x99 \|\| b[4..7] \|\| ACK \|\| Sets sensor range. Note that parameter bytes differ from those in the datasheet.
	\|-		\|-
	\| 0x9A \|\| b[4] \|\| ACK \|\| ???		\| 0x9A \|\| b[4] \|\| ACK \|\| ???

Disasm: /* Protocol (operation mode 0) */

2019-10-01T17:13:22Z

Protocol (operation mode 0)

← Older revision		Revision as of 17:13, 1 October 2019
Line 115:		Line 115:
	\| 0x87 \|\| b[5], b[6], b[7] \|\| r[2], r[3..6] \|\| ???		\| 0x87 \|\| b[5], b[6], b[7] \|\| r[2], r[3..6] \|\| ???
	\|-		\|-
	\| 0x88 \|\| b[3] \|\| ~~???~~ \|\| ???		\| 0x88 \|\| b[3..4] \|\| r[2..3]=b[3..4] \|\| ???
	\|-		\|-
	\| 0x8D \|\| \|\| no response \|\| MCU reset		\| 0x8D \|\| \|\| no response \|\| MCU reset