Saw the stuff on DS18B20 sensors. I have had quite a few fail for various reasons and know quite a bit about the failure modes. First ones were hand soldered by me to CAT5 cable with heat shrink over each pin and then heat shrink over the assembly. They started failing in less than a few months…

[image] stephen: pt1000 that I have not started using yet – do you mind if I ask what the math for them I’m rich in flash space in this application so I used a spreadsheet to build me a lookup table of tenths of a degree, along the lines of: static const int16_t temp_lookup[4096] = { -457, -…

Just to throw in comment (or 2) about the ds18b20’s, I’ve heard, here and elsewhere that they can be troublesome, but I have used hundreds of these and never had one fail. I cannot say i haven’t had some duff reading but they are rare and the majority get filtered out, resulting in a missing reading…

all good advice. This is what I use: [image] orange solid +5V (pin 3 of sensor, pin 1 of RJ45) [image] white/brown stripe Data (pin 2 of sensor, pin 2 of RJ45) [image] brown solid Ground (pin 1 of sensor, pin 8 of RJ45) I follow T568B [image] so the pins I use will be on pairs that are le…

[image] Frogmore42: incase they are accidentally plugged in where they shouldn’t be. also good advice :slight_smile: I avoid using RJ45 if I can, but when I do I make sure they are the right type for the cable, did you know (I assume you do) the “usual” RJ45 are intended for multi-strand and…

So what sort of maximum cable length are you guys finding you can get to? I guess it depends a lot on the topology along the way, but maybe with just one sensor say?

I can’t say I’ve ever really pushed the distance very far. I did make up some sub-assemblies with 8 or 10 ds18b20’s across an approximate winding 10mtr cable span and left them soak testing for a month with 20mtr tails (coiled up), I have no idea what the finished length was once they installed the…

There’s an app note for that: https://www.maximintegrated.com/en/app-notes/index.mvp/id/148 I have never tried to push the distance. 3 meters is about as far as I have tried.

[image] pb66: eg when I connect ds18b20’s to a RPi, I will power them from 5v rather than the 3.3v 50mA rail. Do you need a level converter on the data pin in that case? What strength pull-up do you use with 5V? EDIT - or do you power it at 5V but pull the data line to 3.3V?

[image] dBC: Do you need a level converter on the data pin in that case? Theoretically I guess so, but no, I don’t use any level matching. [image] dBC: What strength pull-up do you use with 5V? The usual 4K7 or sometimes a 5K0 depending what I have to hand. [image] dBC: or do you…

[image] pb66: 99% of all vehicle electrical faults basically end up being a problem with 1 of 3 things, connections, connections or connections. Especially the corroded ones! :wink: :grin:

Community

OpenEnergyMonitor

Home
Docs
Community
Shop
Search

OpenEnergyMonitor Community

DS18B20 reliability considerations

Hardware

ds18b20

show post in topic

Home
Categories
Guidelines
Terms of Service

Powered by Discourse, best viewed with JavaScript enabled