How to Power DS18B20 Over Long Distance

[bostonman]

What is the best way to get low voltage over long distances to power a one-wire DS18B20?

I could use higher voltage AC, but then I need circuitry to reduce the voltage to DC.

[ledtester]

What kind of distance are you attempting to communicate over?

This discussion has some ideas:

https://forum.arduino.cc/index.php?topic=21762.0

And it mentions this Maxim app note (#148):

https://www.maximintegrated.com/en/app-notes/index.mvp/id/148

A solution for up to 200m is outlined in Appendix A.

[oPossum]

Power is easy because 1 wire devices are usually very low power. The hard part is reliable communication. Open collector buses are not well suited for long distance.

[bostonman]

What kind of distance are you attempting to communicate over?

Probably 50'.

It may be a question of the best way to just get 5V DC over long distances rather than focus on a specific device.

Does one just increase the DC voltage at the beginning to get 5V at the end? If so, then what if you're powering one device 1' away and another 50' away?

[ledtester]

It may be a question of the best way to just get 5V DC over long distances rather than focus on a specific device.

How much power do you need to deliver?

You can use the "AC power line" trick to reduce the voltage drop due to wire resistance with DC by using a DC-DC buck-converter at the device -- that's how power over ethernet works.

[Basement ScienceE]

Probably 50'.

That´s like 15m, right?
In that case there should be no problem at all. I have a huge 1-wire bus running through the entire house, with around 30 DS18B20s and some other devices connected to it and I think more than 100m of cables (CAT7). They run all over the place, there are many dead ends etc.

One easy thing you could do is add some 100nF capacitors next to all/some of the devices from +5V to GND. That should keep the supply voltage for the 1-wire device more stable. However in my case, there isn´t a single one of those installed in the entire system.

[bostonman]

How much power do you need to deliver?

I somewhat deviated to ask how one would in general deliver low DC voltage (5V) over long distances. As for power, again, it was more general, so let's just say tens of milli-amps.

I have a huge 1-wire bus running through the entire house, with around 30 DS18B20s and some other devices connected to it

How do you monitor all these? This seems similar to the project I want to incorporate into my house.

[Basement ScienceE]

How do you monitor all these? This seems similar to the project I want to incorporate into my house.

We used a software called IP-Symcon running on a raspberry pi 2.
I have plenty of complaints with it, and it´s not free. I wouldn´t necessarily recommend it. You have to program everything in PHP of all things and there is only support for a few types of 1-wire devices. But it does allow you to display everything as a website.