I started a temperature logging project like described in Particle Make. Nine DS187B20 sensors are connected to a Photon collecting and sending the data every 15 seconds to a 20x4 serial connected LCD and sending 9 temperatures every three minutes to a Google Spreadsheet via IFTTT.
With a small number of adaptations on the basic program, the system is working perfect except for one element : the stability of the temperature-data. 30 to 50 times a day I find -0.1 readings on my LCD and on my spreadsheet.
I already adapted the “wait” times in the program from 250 to 1000 and more. I also was adding a"wait" after the read-instruction etc… This changes have a positive effect but I still find -0.1 readings.
I tried varying the pull-up resistor from 4.7 K to 1 K and I have the impression this has the best result although it isn’t yet 100 % solving the problem. In the same sense,I can, of course further diminue the value of that resistor. But maybe this isn’t the best solution.
My question is : for the moment the DS18B20 sensors are fed with 3.3 V from the Photon. At the same time my LCD is fed by 5V from the VIN-pin from the Photon.
Could it be a good solution to power also the sensors with that 5 V pin as the specifications of the DS18B20 says the minimal feed-in power is 3.3, but this can go up to 5.5 V as described in page 2 of the specification sheet from Maxlm Integrated ?
In other words ; why should I further diminue the value of the resistors if I can highen the feed-in line ?
Thanks a lot for your suggestions.