Ok I’m confused… and not sure whats Going on ! Cheap clones ?
I have a Brewpi threaded DS18B20 sensor from the store which works and is seen by my version of the Brewpi Spark and so do several sensors from my Arduino Brewpi’s with a rev A and C shields. I bought a batch of 5 with 3M leads from an Amazon supplier (based in China) as part of my HERMS build and none of them were recognised on the Spark or on the Arduino Brewpi’s , So I ordered a second batch from an ebay supplier, thinking the first batch were fakes or clones…, to my surprise the second batch, ditto none of them were recognised. Something odd was going on !, so Out of curiosity and frustration I got a 3rd Batch of 5 from a local UK based Amazon supplier, this batch works…
I couldn’t believe that the first 2 batches could all be faulty, maybe they were another variant , so I dug out my Arduino Mega 2650 fired up Sketch and tried a very simple DTH test sketch and the Dallas Tester Sketch with a ‘faulty’ sensor on one of my hacked around DIY shields…I was surprised… it Worked !
I even added in a second ‘faulty’ sensor and both are seen and both start 28 indicating they are 18B20’s and not the 18s20 as I initially thought? and now I am confused…!! they work on the Arduino mega but aren’t seen by the brewpi’s.!
below is the serial output from the Dallas Tester sketch…
Temperature for device: 1
Temp C: 20.75 Temp F: 69.35
Requesting temperatures…Dallas Temperature IC Control Library Demo
Locating devices…Found 2 devices.
Parasite power is: ON
Found device 0 with address: 2862D11E00008081
Setting resolution to 12
Resolution actually set to: 12
Found device 1 with address: 2811EF1E00008066
Setting resolution to 12
Resolution actually set to: 12
Requesting temperatures…DONE
Temperature for device: 0
Temp C: 23.56 Temp F: 74.41
Temperature for device: 1
Temp C: 20.75 Temp F: 69.35
Requesting temperatures…DONE
Temperature for device: 0
Temp C: 23.56 Temp F: 74.41
Temperature for device: 1
Has anyone had similar experiences ? is it that they are clones ?
I’m not to sure but I am in the middle of building my brewpi and had the same issue… The Uno would not recognize the sensors. Thinking it might be my cheap board I replaced it and still a no go. So I tore apart a probe to see how the wires were connected to the ic since the Pi program will not recognize probes in parasitic mode. Wires were connected correctly. A person on the homebrewtalk forum drew up a quick arduino sketch to determine if or probes were running in parasitic mode. I took the sensor I tore apart and ran the sketch directly from the leads. Parasite mode ON. So seems this vendor has the DS18B20P vs Ds18b20. Mine were purchased from Amazon 5 pack 3 M leads hilti brand or something. 2 others on that forum have had issues in the past week. At least one other had same brand.
Yes, all these issues seem to come from the sensors being some parasitic power only version.
We hide parasitically powered devices, because they cannot do a reliable temperature conversion every second.
It seems to be that an amazon seller has been selling probes that only support parasitic mode, which BrewPi does not support. We ignore them on purpose, because parasitically powered devices have proven to be unreliable in the past. If a device was parasitically powered, this usually meant bad wiring.
Someone on HBT made a test sketch to see if yours are parasitically powered. You can find it here:
Hi Elco, is there any way we can get a configurable switch to allow parasitic mode? I’m in the same boat with the 5 that I ordered. Mine are only 1m long and it sounds like the risk is with longer wiring setups. I’m willing to risk them only responding every other second if need be.
No, sorry. I don’t want to go down that road. We disabled parasitic power for a reason.
If you can compile the software yourself, feel free to hack it out. We are not doing updates on Arduino anymore.
These sensors are so cheap, do yourself a favor and buy good sensors.
Ok, thanks for being upfront and your suggestions.
I think the cheapness of the sensors is exactly the issue here as we as consumers can’t tell if they are going to be grounded across their vcc pin which forces always parasitic mode.