1-Wire: topology limits & design guide

Hi,

we started to build a 1-Wire DS18B20 temperature sensors network connected to the Sensor module (https://shop.hardwario.com/sensor-module/).

It is relatively easy to deploy a couple of sensors, but our network tends to be more complex and it brings us to a state when some sensors are not read.

Could you please give any maximal parameters for 1-Wire topology (limits for length and number of devices) with the Sensor module?

What are your recommendations for 1-wire network design?
(e.g. base on https://www.maximintegrated.com/en/design/technical-documents/tutorials/1/148.html)

Thanks!

Hello,
that PDF from Maxim is the best what you should stick to. If you share for example sketch of your current topology we can take a look what could be improved.

  • Which revision of Sensor Module do you use?
  • How many sensors do you have?
  • Do you have DS18b20 sensors from us, or other types of 1-Wire sensors? (so we can know what are we dealing with)
  • What cabling do you use?

Ideas what to improve/try:

  • Try to decrease the pull-up resistor value
  • Try to add capacitance to power-rail (1-10 uF accross some sensors)
  • Few months ago we’ve updated in SDK more relaxed timing in sensor detection
  • Comment out automatic power-off - it does not have huge power consumption effect, keeping voltage stable on big bus could be better idea

Hi,
we did some more improvements in DS18B20 code. If you give me more info (see previous post) and give me the name of firmware you use I could build newer version so you can test it. Or in case you compile firmware yourself, I can guide you how to update SDK and code.