LYWSD03MMC in the freezer

[evlo]

I did put one LYWSD03MMC into the freezer and it stopped measuring at 3.55C and does not go lower, temperature is definitely bellow zero, batter voltage doped as expected. I remember previous winter some of these I have outside measured negative temperatures.

I do understand it is quite sudden temperature and voltage difference - but what is going on? why it stopped reporting at 3.55C? Will it go lower after some time?

I can still connect to it using https://pvvx.github.io/ATC_MiThermometer/TelinkMiFlasher.html and there i get -0.01C

and now even

Update:

[MacSass]

As far as I know those are intnded for indoor only and thus not rated for below 0 unfortunately.

Measure range 0°C-60°C

Temperature display resolution0.1°C

Humidity range 0%99%RH

Humidity display resolution1 %RH

I had seen a previous discussion on this with the same conclusion.

[evlo]

It does measure bellow zero very well, I used it outside over the last winter and had very correct data.
STH40 is -40°C to +125°C, TLSR8251F512ET24 -40°C to +85°C

Weirdness continues

Now it shows -16 and directly on the device -16 too, but why did it take so log to show in Ha?
It took about 30 minuts to update, but in that time it did update battery voltage in advertisement

Don't get me wrong, this is still better than any out of box commercial sensor I tried so far, but I'm quite curious why it it did not update (now it updates again).

I also tested that if advertisement is not received HA does NOT repeat old data and just reports nothing (correct behavior)

Now everything seems to work after a while, just reported +3.55 and then jumped to -15.99 after about 30 minutes

Another update, now:
Vbat: 2272 mV , Temp: -18.42°C, Humi: 50.69%, ID: 30560, Reed switch counter: 0, flg: 0x0E:r0/t1
and reporting -18.13 °C for about 10 minutes.

So I move one of my esphome BT gateways near the freezer and it still reports -18.13 in HA while in TelinkMiFlasher it show -18.41°C

Maybe it is just bad reception and for some reason it repeats last seen data as device is online or something?

[evlo]

weird that it is getting stuck like that

other devices that are same hw and fw do not have these dropouts

maybe it is secret battery saving measure?

and to add to confusion display go stuck at -14 (thought similar thing with stuck display happened when i let on in the sun) and battery symbol was showing.

Thought this one i used does have same 2032 in it for two years now, so I will buy more sensor and do a test with fresh batteries.
Maybe related #265 (comment)

[pvvx]

Regular CR2032 do not work in cold.
The typical maximum is -32C for a new expensive CR2032 battery. The voltage drops below 2.0 V.

[pvvx]

https://github.com/pvvx/BLE_THSensor

2 AAA battery

Work in the refrigerator freezer (BTHome v2, BLE LongRange for stable long-distance communication through the iron walls of the refrigerator):

[scottcopus]

I currently just have a single LYWSD03MMC (HW B1.5 I think) for now but looking to buy more. The hope is to put a few of them in my fridge/freezers. BTW, if anyone has any good US sources for these let me know.

Does anyone know the max battery supply voltage the LYWSD03MMC can accept? I'm looking for a way to "mount" a square-ish rechargeable battery on the back of this and maybe rig a battery connector plug thru the side of it. I've also got a lot of NiMH AA & AAA's and I guess I could always use a two-battery holder. But is the minimum temperature limits for both NiMH and Lithium-ion batteries -20C? Which is about what most freezers are running? 😱❄️

[DavidStacer]

I modified one to take a CR2450. #396
Just simple tools required.

[pvvx]

The maximum supply voltage for the chip is limited to 3.6V. When higher voltage is applied for a short period of time, the chip degrades. Subsequently, it will continue to work, but with increased consumption.

Such experiments were carried out repeatedly. After connecting a voltage above 4V, all chips degraded. When the voltage dropped to the normal level of 2..3.3V, such chips began to consume significantly more, but continued to work.

[scottcopus]

Thanks @DavidStacer. I actually saw your mod post. Thanks for sharing. I'll comment over there with a couple related questions soon.

Thanks @pvvx. Would you say the entire LYWSD03MMC thermometer (at the battery terminal) should be limited to 3.6V, or reduced further to prevent damage to other components like the sensor? If using a 3.7V lithium-ion or a 3-cell NiMH holder (1.2V x 3 = 3.6V), would a diode-based voltage drop work, or would you suggest sticking with an LDO like an MCP17xx or something else? Just curious what you think. For my cold freezer installations though, I might stick with regular alkaline 2 x 1.5v AA/AAA and see how the batteries fair after some weeks/months.

[pvvx]

Sometimes one diode is enough. Or two in series connection. But the best option is LDO.
MCP17xx is not the best in terms of its own consumption...

[pvvx]

For my cold freezer installations though, I might stick with regular alkaline 2 x 1.5v AA/AAA and see how the batteries fair after some weeks/months.

#377 (comment)

[scottcopus]

On my LYWSD03MMC I've got a reed switch connected on it. But for some reason HA doesn't always catch when the reed switches on/off or can be delayed for several seconds. My intent was to catch when my doors (fridge/freeze/any door) opens and closes. Does anyone know what that is? Are reed switch events always fired off thru BT instantly? If not can be it configured to?

FYI, I'm using ESPHome bluetooth proxy on a ESP32 (TinyPico).

BT firmware log:
4:46:24 PM: Hardware Version: LYWSD03MMC B1.5, Software Version: 4.3, Sensor: SHTC3 (SHTV3)
4:46:24 PM: Custom config HEX string: 55171000002804a931318ab4

[pvvx]

The message about the activation of the reed switch is transmitted 3 times with an interval of 50 ms.

On the receiving side, the first message about the activation of the reed switch is processed 5..7 ms after the change in the contact state.

On ESP devices running both Wi-Fi and BLE, there are periods of more than 1 second when they are not receiving anything. This is due to working with WiFi.

[pvvx]

FYI, I'm using ESPHome bluetooth proxy on a ESP32 (TinyPico).

Reason for using ESP.
ESP misses a lot of receptions from BLE devices:

• Overloaded software. Low processing speed.
• Most of the time the antenna works on Wi-Fi.

ESP is not recommended for use in BLE.
Also, the ESP software processes receiving packets very slowly on a BLE connection. The battery device has to duplicate the transmission of each packet many times, which consumes a lot of battery power. Measurements show a fifty-fold increase in battery power consumption when connected to ESP.

[scottcopus]

Sorry for the confusion. I wasn't asking for a firmware code change. I was just asking if it was possible to tweak any settings that could improve when using the lacking ESP devices. That's why I also asked about switching to something else other then Espressif devices. ;)

What's your setup (or what would it be) for reliably receiving all BLE advertising packets from distant sensors and getting them into HA?

When you say BT sniffer, are you referring to 'software'? For example, is there an Android BT sniffer app that can relay directly to HA? If so an Android phone could be a distant BT gateway? Forgive my lack of knowledge in this area.

[pvvx]

There are firmwares for nRF with sniffer functions.
For other chips too.
Even this option accepts more packets than ESP - https://github.com/pvvx/AdScanerTrg

For Android you can directly in explorer and js - https://pvvx.github.io/ATC_MiThermometer/Advertising.html

Android has 'nRFconnect' and many other programs that work with BLE advertising in Bluetooth 5.0+ format (PHY 1M/2M/Coded: 250/125k - LE Long Range). They are written using the standard Android API. This is not possible on Linux and Windows.

Bluetooth Web API, Bluez, Bleak, Home Assistant, ... is limited (BT 4.2) due to Linux functionality (kernel and drivers not developing since 2016).

[pvvx]

For example, is there an Android BT sniffer app that can relay directly to HA? If so an Android phone could be a distant BT gateway?

These are commercial projects and devices. I am not their distributor. Let them make money from this disgrace in Linux.
When Linux is fixed, perhaps I will propose an open source project.

[evlo]

Kinda different topic, but I think reed switch might in the end be same thing as button press.

In my experience ESP32 (or ESP32-s3) is ok in connected mode (example here https://github.com/wifwucite/esphome-ble-controller ).
Even if it did not get 100% of the send messages (it does in my environment), there is under 100ms delay so people would just press the button again.
This is while both sender and receiver are esp32-s3 devices connected to the wifi AT THE SAME TIME too.

I'm still not 100% sure I fully understand difference between bluetooth connected and advertisement mode.

I do have 2 esp-s3 esphome gateways that do nothing else than being a gateway, and 4 that are on devices that do primarily other stuff.

For the advertised button press I still do not get quite a few in home assistant.

I'm thinking in my target usage, when I would like to advertise button press and react on it (basically event driven wireless "bus") [so all the advertisers just advertise the press and all the receivers decide whether to react to it or not] there might even be issue that as there is lot of sensors broadcasting measurements, button press advertisement packets just collide with other stuff that is advertised on BLE at the same time. So the result is the same as when two people start talking on same VHF frequency on walkie talkie at the same time. But maybe ble is not affected by this?

My experience with other stuff like zigbee or z-wave battery powered devices is worse in the end result (pairing, coordinator, mesh vs gateways, no real control over he devices). I'm now thinking maybe rf433 for the battery operated buttons might be a way to go. [so far I found out that rf433 buttons I tested need to be held for exact time otherwise they do not send the whole message 🤦 ]

For the thermo hygro meters I don't care at all about few missed advertisements, for the buttons it makes the thing, for me, in the end, unusable.

Is there a way to use something like RTL8761 as a esphome ble gateway? (it works connected to the server running HA directly, but that is different thing).
I do not even have HA server in the same county in one case :)

[pvvx]

But maybe ble is not affected by this?

This is called a collision. For this reason, advertising messages in BLE are repeatedly duplicated.

It is impossible to confuse who the message is from. The message contains the MAC address of the device.

The WiFi specification has Bluetooth device detection to reduce collisions. But not in ESP.

[evlo]

For example, is there an Android BT sniffer app that can relay directly to HA? If so an Android phone could be a distant BT gateway?

These are commercial projects and devices. I am not their distributor. Let them make money from this disgrace in Linux. When Linux is fixed, perhaps I will propose an open source project.

There are? I'm not able to find anything, but having (old) phone act as HA ble gateway for advertisement would solve the processing power issue easily.

Maybe again something got lost in translation for me.

[pvvx]

Use it, who forbids it?

[evlo]

I do not understand how to set that up.

Only somewhat related thing i found might be this https://www.mysensors.org/ ?

I think I mainly do not understand how ble gateways in HA work.

[pvvx]

Sample: https://apps.rustore.ru/app/ru.kompius.thermo_plung
Supports LE long-range variant as well.

[evlo]

Oh ... the way is to use mqtt in the middle, did not occurred to me to to do it that way, thank you!

[pvvx]

Automatic translation (https://apps.rustore.ru/app/ru.kompius.thermo_plung):

Designed for working with various wireless (BLE) temperature sensors, humidity, electric meters, etc.

It also allows you to connect to the data collectors (MQTT) for reading or transmitting measurements.

It is possible to connect 1 Wire sensors DS18x20, DS1990 (Ibutton) directly to the smartphone via OTG USB-Serial Converter (for example, CH340).

In the current version, the following sensors/devices are supported.

1. BLE GIGRO-thermo-rods of the production of NTC Compius LLC.
http://kompius.ru/

2. Xiaomi sensors both with the original firmware and optimized.
https://github.com/pvvx/atc_mithhermometer

3. Wire DS18x20

4. Electric meters CE308/208

Main functionality:

- search for devices in the area of the BLE SMARARTFON;

- reading data both from adversizing (advertising packages) and by installing the connection;

- data visualization: a list, on a grid, in the form of history trends;

- interaction with MQTT by a broker (reading, recording of readings);

- creation of user groups of devices;

-communication with data collectors (LLC "NTC Compius") for the formation of regular PDF reports sent to e-mail;

- Setting up variable sensors parameters.

Detailed documentation on the application page:
http://kompius.ru/products/48776765

The author does not provide source codes.
The author explains this by saying that there are a lot of examples of the Android API and writing your own application is very simple.
I have not communicated with other authors of similar software...