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Information on 1-wire please

148 Views - Created 16/04/2020

16/04/2020

Posted by:
jdenver

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How many 1-wire devies can I connect to one 1-wire interface board?

(I have 5 x DS18B20's and a ibutton reader im hoping to connect.)

Can I add a ADC and IO board to the same pi3+ as the 1-wire board or would it cause problems?

 

I will be using this to add inputs and outputs to Home Assistant running on a NUC, how would the raspberry pi comunicate with the NUC? Im asuming through the LAN if thats possiable.

 

 

Kind regards

16/04/2020

Posted by:
andrew

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United Kingdom

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Hello

The maximum number of devices you can connect to a 1-wire bus is depedant on several factors such as cable length and outside interference but there shouldn't be any problems with using 6 devices on a bus.

Maxim has a good tutorial on their website on building reliable 1-wire networks, you can find it at https://pdfserv.maximintegrated.com/en/an/AN148.pdf

You can connect the ADC Pi, IO Pi and 1-Wire Pi to the same Raspberry Pi.  I would recommend stacking the 1-Wire Pi on top of the other two as the RJ12 socket on the 1-Wire Pi is the same height as the mounting kits so it can be a tight fit with other boards stacked on top.

You should be able to send the data from the inputs and outputs on a Raspberry Pi to Home Assistant on an NUC over the LAN.  One method would be to use an MQTT broker such as Mosquitto on the NUC to act as a message store.  The Raspberry Pi can then publish MQTT messages to the broker each time an input or output changes and Home Assistant can subscribe to the MQTT broker which would notify Home Assistant when a new message arrives.

AB Electronics UK Tech Support

16/04/2020

Posted by:
jdenver

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Thank you for the links

Quote from andrew
One method would be to use an MQTT broker such as Mosquitto on the NUC to act as a message store.  The Raspberry Pi can then publish MQTT messages to the broker each time an input or output changes and Home Assistant can subscribe to the MQTT broker which would notify Home Assistant when a new message arrives.

Are there any other methods? Ive have used MQTT before but was wondering what else was out there for connectiverty.

 

Thank you, Regards.

16/04/2020

Posted by:
andrew

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I don't have a lot of experience with Home Assistant so I am not sure what other methods of communication it supports.  The only method I have used is MQTT.

The Home Assistant forum may have more information on how to communicate between a Raspberry Pi and Home Assistant.

AB Electronics UK Tech Support

20/04/2020

Posted by:
jdenver

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Will your 1-wire board support parasite powered 1-wire devices?

20/04/2020

Posted by:
andrew

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I have tested our 1 Wire Pi Plus and Zero boards with the DS18B20 temperature sensors and several iButton devices using parastitic power and they do work. 

If you have several devices connected over a long 1-Wire bus then I would recommend using powered 1-wire devices as you may find that the voltage drop on the bus makes parasitic devices unreliable.

AB Electronics UK Tech Support

20/04/2020

Posted by:
jdenver

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Thank you, just ordered a board #13580 so looking forward to trying it out.

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