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Humidity & Temprature sensing 1-wire

Added by Jas2 about 5 years ago

Hi,

I can get the DS18B20 1-wire temperature sensor for about 1euro each.
Does anyone know of a sensor, as reliable as this one, that has temperature and humidity, for 2 euros each ?

Thanks

Jas

www.projects.privateeyepi.com/home/temperature-sensor-project-using-ds18b20


Replies (4)

RE: Humidity & Temprature sensing 1-wire - Added by padvinder95 about 5 years ago

The DHT11 and DHT22 come close to this price (on eBay, at least) and offer temperature and humidity readings—the 22 somewhat more accurate, or at least precise, than the 11.

RE: Humidity & Temprature sensing 1-wire - Added by Jas2 about 5 years ago

Hi Padvinder ! :)

Thank you !

This doc www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf
says
“it’s different from Maxim/Dallas 1-wire bus, so it’s incompatible with Dallas 1-wire bus”

Do you know if it can be used with the DS18B20 on the same bus ?

:)

Jas

RE: Humidity & Temprature sensing 1-wire - Added by padvinder95 about 5 years ago

I don’t think it would be a good idea (read: it’s impossible) to use this one on a 1-wire bus, since it really uses a different protocol: there would be no way to select the DHT/AM2302 without also (accidentally) speaking to a 1-wire device, or vice versa. Like it says on the Adafruit page: this device does not have bus communication, and each new sensor needs its own data pin. (Alternatively, you could connect all data pins together and turn the devices on in turn, but then you’d need a separately controlled power pin for each device.)

If you really want a lot of sensors on 1 µC, you need a device that uses a bus for communication: I2C (sometimes called Two-Wire Interface) or the 1-wire Dallas bus. That functionality comes with a higher price. I know of one way to hack around this: people have used the DS2438 (1-wire) smart battery monitor in combination with a relatively cheap analog-output humidity sensor: the DS2438 has an A/D convertor to monitor battery voltage, and a built-in temperature sensor to monitor the battery heat production. If you use its A/D to measure the analogue humidity sensor, you get a One-Wire hum+temp sensor. This is a lot of hack work, though… Another option is to use the Analog Input plug (12 A/D channels) to interface to 12 analogue-out humidity sensors, but those analogue humidity sensors are still a couple of euros.

RE: Humidity & Temprature sensing 1-wire - Added by ull about 5 years ago

Hi

I’m using 1-Wire ADC DS2438 (about 5€) and HIH-4030 analog humidity sensor (about 6€) - both from tme.eu to monitor temperature and humidity indoors. My design is open source, schematics and board layout files are attached in Eagle 6.5 format.

Also I designed a JeeNode compatible plug/board for better 1-wire performance. It includes a level shifter from 3.3V to 5V and a DS2482-100 i2c to 1-wire converter chip. The board also has a mosfet for strong 1-wire pull-up but i don’t actually use this feature. 5V low drop-out regulator is also needed to provide 5V voltage to 1-wire from JeeNode power bus. I’l also include Eagle files for this little adapter board. It has two versions, v2 has footprint for rj12 socket and v3 should fit both rj12 or rj45 socket for convinience.

Oh and there is also a library that enables all these things ant these are also open source… I should probably upload all this stuff to github.
I have some pcb boards and pre assembled versions in stock if anyone is interested to buy instead of making them yourself :)

Update: more info on new website: https://taaralabs.eu/oh1

Cheers,
Märt

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