DS18b20 powering up in different way

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Hi there,

I’m using on my system a few DS temp sensor connected in standard mode to RPI (power in to rpi +3V3 pin 1, and data out to GPIO 4, 4k7 resistor between V+ and data). All works fine from several years.

I want to add 2 more DS sensors, but there is a wire limitation, and I have at this place only the +5V, GND, and the data wire from the RPI. First i placed a 3V3 stabilizer IC for supply these 2 sensors, the system recognized the sensors, but the values are readed wrong (-180 ~ -200 grade C). After this i built a voltage divider with 2 resistors, but the system become very unstable, all the sensors appeared / disappeared randomly.

Can anyone have similar situation when multiple DS sensors must be powered in different way?

Can be the default GPIO 4 (input for DS sensors) changed to any other GPIO?

Thank you

Zoltán, did you try to wire the sensors in star-like topology. I found this suggestion on one of the threads on the matter. This is to ensure all sensors have about the same cable length. It might be difficult to achieve this in real-world setup though where sensor are distributed to several rooms in the house. Anyway cable length might be an issue.

https://lb.raspberrypi.org/forums/viewtopic.php?t=167896

EDIT: The example above is also suggested in the vendor design documentation. There also some more hints to check out.

https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/148.html

Hello,
my PI3+ works with 12 pieces of DS18b20 as heating sensors for the flow with cable length on the 1-wire bus of approx. 7m length interference-free. The power supply is not provided by the PI. I have a switching power supply, which provides 5V (30W) and with it I fire PI, USB hub, Ardoino´s and the DS18b20. Since one year trouble-free. A source of interference was once a defective switching power supply for a monitor.

MfG, Jens.

Translated with www.DeepL.com/Translator

Hi!

It looks like i solved the problem.
The only way to get working several sensors, with different cable length is using an extra 5V power supply for the sensors, and at the each node of nearby sensors to build a voltage divider like this:

There need be strong common GND for all node, and with R2 potentiometer al node +3.3 V must be adjusted at the same potential.

Thank you folks!

But the second question is still available - can be the GPIO 4 changed in DS18b20 plugin?

I don’t use gpio at all. I can only give you a link of what I use for my ds18b20 (9 items with 25m cable ) https://www.abelectronics.co.uk/p/60/1-wire-pi-plus

@zoltán if I’m not mistaking it’s not the plugin but the one-wire library that has GPIO4 as default.

It’s something in config.txt

dtoverlay=w1-gpio,gpiopin=x

https://pinout.xyz/pinout/1_wiret