My issue is a bit not related to Blynk or can be considered off topic but as I am using Blynk for it I decided to post it here maybe there is something I am missing.
I am using ESP12F on a custom PCB connecting it to 3 DS18B20 sensors on the same 1-wire line. The Vcc of the circuit is supplied by 360mini DCDC converter and the DCDC is set to give 3.33V from a 220V to 6V 2A adapter.
The system works perfectly when at my home. I have a small grocery shop and i thought about putting the sensors in one of the refrigerators that is in the range of -4 to 10 degrees in temperature. When I connect it to the refrigerator, it just keeps giving almost all the readings -127 except few readings only. Most of the time I will have only one sensor of the 3 giving the right reading and the others -127. The cables of all sensors are extended to be 3m and the power adapter too is 3m.
Is this a hardware problem? An error with the code? The AC DC adapter is not getting enough current because the refrigerators? It is just driving me crazy!
While we try to assist… we also try to keep this forum relevant to its purpose… learning how to use Blynk, not the ancillary aspects of hardware, networking etc. Yes they are related… sorta… but you don’t buy a car then ask the dealer for help planning the proper hotels to stay at on a road trip… just becasue you plan on driving the car they sold you
Basically all the idiosyncrasies of these sensors can, and are, heavily discussed and resolved in great details on hundreds of sites across the Web…
If it works on the bench, then it is probably hardware related… first off, -127 it the standard error meaning no signal.
And yes, unless you have a good isolated PSU or perhaps battery, then there may be problems due proximity to the potential interference from the compressors.
And probably obvious, but one never knows the device itself shouldn’t be in the fridge, only the sensor.
And since you have this length, then I suppose the previous comment is irrelevant but back to the cable, 3 meters might be long enough to cause signal degradation… so much depends on how you run them, direct power, parasitic power, where is the resistor, are the cables shielded, the gauge of the wire, 5v or 3.3v…
So many potential issues and well beyond the general troubleshooting purposes of this forum.
3m cable is negligible for 1-wire . First double check wiring connections for integrity.
-127 means bad or no communication. You should provide (if you don’t) external power to the Vcc pin of DS18B20. Use pull up resistance down to 1-1.5kOhm.
I use 3.3V for pull-up (and 1-wire voltage level), but 5V for external power.
Bit-banging is not the best way to realize 1-wire master, but i have a test unit (ESP12E) and two DS18B20 running reliably with 20m UTP cat 5e cable
I use NODEMCU which is 5VDC powered and delivers 3.3V internally. A 5V 1A power supply is more than enough
If you use two, you may use 1A for 3.3VDC (overkill) and the smallest possible for 5V. each one DS18B20 draws 1.5mA max during temperature conversion (this is where you need the 5V assistance)
but back to the cable, 3 meters might be long enough to cause signal degradation… so much depends on how you run them, direct power, parasitic power, where is the resistor, are the cables shielded, the gauge of the wire, 5v or 3.3v…