This sealed digital temperature probe lets you precisely measure temperatures in wet environments with a simple 1-Wire interface. The DS18B20 provides 9 to 12-bit (configurable) temperature readings over a 1-Wire interface, so that only one wire (and ground) needs to be connected from a central microprocessor.
Hello. I just bought the “Temperature Sensor - Waterproof (DS18B20) SKU: SEN-11050” but I connect get it to work. I couldnt find information on your website, but I assumed that the white wire is the signal, red is power, and black is ground. Is that right? I connected it to my Fibaro Smart Implant FGBS-222 and it does not show any temperature reading. The software reports “Null”. However I can make other readings on the Fibaro.
That’s really strange, I have had a quick look through the Fibaro documentation for that device and it looks like it should be able to use this sensor. Can you let us know what you have each wire hooked up to with your Fibaro? It may also be a software issue here as I cant find a lot of info on how the integration works with these sensors, though we can keep looking into it and see what we find.
Thanks for posting, can you please check pages 8 and 10 of this User Manual for the Fibaro that you’ve got. It covers in detail how to connect and use the FGBS-222 with the Maxim DS18B20 temperature sensors. Please let us know if you have any questions about it:
Thanks Bryce for giving me the link to the FGBS-222 manual. I read pages 8 and 10, and confirm I connected the DS18B20 (SEN-11050) correctly. However it is still not working. I will keep looking, but if you have any other suggestions I can try, please let me know. Thanks!
I connected the Smart Implant to a 12VDC regulated power supply. The Smart Implant seems to be working, as I can receive the internal temperature reading, and I can activate its output switches. So I am not sure why there is no data reported in any of its 6 temperature channels which relate to the DS18B20 input.
Thanks Blayden and Liam. I managed to find another DS18B20 and connected it, and it too didn’t report any temperature. So its looking like the software (OpenHAB), even though it apparently has installed the temperature sensor channels (I installed all 6 allowed for the Smart Implant). If I manage to get it working, I will post a response. Thank you.
Thanks Hotswapster. I tried a 4k7 resistor from data to ground, and also data to power as written by someone who advised this for the Smart Implant. Link below. Neither worked unfortunately. My access to other devices to connect to is limited, but I agree that the next step to debugging is to try get the sensors to work on something else. I will post here if i get any success. Hopefully soon!
How unusual, if you find that you run into any issues with using the DS18B20 with other boards please let us know.
About three years ago there was a widespread release of non-Maxim unlicensed DS18B20s that got put out onto the market, there’s a few open source projects such as the repo I linked below that look at the ROM on the chips to verify if they’re counterfeit or not.
I personally tested all of the Core Electronics stock of various DS18B20 sensors at the time (including these ones) to ensure they’re certainly using the official Maxim chips, but this is certainly something to be aware of for anyone using DS18B20s in their projects or systems:
You should not do that. These resistors will form a voltage divider and will rest at half supply voltage. One or the other or none but not both.
For that arrangement to work the data would have to be driven HIGH and LOW in which case neither would be required. If a pull up or pull down WAS required by having both the data pin would only go to half supply when the pull up or down was needed and would never go all the way to supply volts or ground.
EDIT: Just had a look at that tutorial. There is NO mention of a PULL DOWN resistor. Just a pull up. This would be normal. Easy enough to established if one is fitted or not
Measure the resistance between supply voltage and data line. Resistance (4k7 or whatever) present, pull up fitted, open circuit, not fitted. Measure with no power applied or you will probably fry the meter.
How simple is that. In all the posts I have read I have not seen this method once. Usually on visual inspection or someone who knows for sure publishing the fact.
Glad to see Bob is on the case here and saw that one. Might be worth trying the pull up resistor and if there is still some trouble with it, its worth testing the sensor on an alternate device to rule out the sensor itself being the problem.
All the info required seems to be in the data sheet linked from the product page.
A quick browse turned up the following.
“* Requires no external components.”
This seems to be the case if power derived from the data line.
“writing, and performing temperature conversions can be derived from the data line itself with no need for an external power source.”
If power is supplied externally as I think is the case here the following arrangement is shown which seems to be pretty straightforward.
According to the text external supply is recommended for temps 100 deg C and above
I have not gone into the Data sheet in depth as it deals with all the technical aspects of the sensor which I have no interest in at the moment but all the basic information is on the first 4 pages. That diagram is on page 4.
I don’t see anything very complicated about that arrangement. I have not looked into the programming requirements for reading these devices. that might be another ball game.
EDIT. The data sheet I think is for the sensor device itself. The purchased device may have the pull up fitted externally. Measure it as described above to be certain.
Just had a quick look at that FGBS-222 linked above and noted the following diagram.
This shows what looks like bare DS18B20 sensors with no mention of pull ups. This suggests that the pull ups might be built into the FGBS-222 device as these connections are dedicated to DS18B20 sensors.
If perchance the waterproof units you have have pull ups built in then that means you will have 7 4k7 resistors in parallel with 6 devices connected which equates to 783Ω. This could be far too low and may be doing all sorts of things like stressing your supply and lowering the available voltage.
I think you need to do some intelligent measuring and find out exactly what you do have in the way of pull ups. I note that you say you have 6 of these connected. Have you tried just 1?? That might be a start. The system should handle that. I think that only 1 pull up should be requires on a line and if that is the case the safest method is to use units without anything built in and install your own resistors where requires. If the pull up is embedded in the parent device then no further resistors should be required.