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Topic: one DS18B20 to multiple devices (Read 144 times) previous topic - next topic

fbs227

Hi,
I've got a question like in the subject, is this possible? One sensor, two different devices?
My furnace driver uses 2 DS18B20 sensors to read the water temperature, can i "hack" them and connect to the Arduino as well?

Thanks

MarkT

You could snoop on the existing communication.  That might be the simplest.

Are they connected in parasitic power mode or not?  If not then multi-master operation might
work as I2C is an open-collector bus.  But there would be nothing to prevent the odd collision
which might confuse the furnace (which might be safety critical issue)...

So I'd say snooping is the safest option.  You are at the mercy of how often the furnace driver
polls the sensors of course.  And I don't know if there's an I2C snooping library you can use.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

pylon

Quote
And I don't know if there's an I2C snooping library you can use.
The DS18B20 uses a OneWire bus and not I2C, so a snooping library for I2C is not really useful.

But I agree that snooping the devices communication is probably the safest option you have.

fbs227

Thank you for help, I think that snooping might be a little bit too dangerous for my furnace driver, if anything goes wrong the furnace might blow out... So I've decided that I will install my own DS18B20 sensors on the pipes in some kind of amateur thermowells (isolation around the pipe and sensor inside, squeezed by a duct tape) and then I will calibrate the readings to fit to those on the driver, it should be much safer option :D

MarkT

The DS18B20 uses a OneWire bus and not I2C, so a snooping library for I2C is not really useful.

But I agree that snooping the devices communication is probably the safest option you have.
Whoops, a braino I think - OneWire is mainly open-collector, especially if not in parasite-power mode,
so the points I make still stand I think.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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