1-Wire: topology limits & design guide

TOWER
1

Hi,

we started to build a 1-Wire DS18B20 temperature sensors network connected to the Sensor module (Sensor Module - HARDWARIO Shop).

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 Guidelines for Reliable Long Line 1-Wire Networks | Analog Devices)

Thanks!

2

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
3

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.