multiple DS18B20 reading 85°C

[pjakobs]

Hi all,

I have an application where I have numerous DS18B20 sensors on one single esp-01.
The general setup works well, but there's always one pesky sensor that reads 85°C - and it's not always the same!
The 85°C is basically the startup value on the scratchpad and usually what you get when you try to read the sensor before the conversion is done.
The original code waits for 800ms, the datasheet sais the conversion should be done after no more than 750ms but still I get 85°C

I have modified _P004_Dallas.ino to include

Code: Select all

  pinMode(Plugin_004_DallasPin, INPUT);
  //digitalWrite(Plugin_004_DallasPin, LOW);
  delay(100);
  uint8_t retries = 200;
  do  {
    if (--retries == 0) return false;
    delay(5);
  } while (!digitalRead(Plugin_004_DallasPin));
  

as suggested for sensors that are not parasitically driven but this still doesn't fix the issue.

Does anyone have any suggestion on this?

pj

[BerndJ]

Hi,

this is the first reset value which is sending from these part.

check yr power supply (best linear driven, not switched), the bus (cable lengtht, R at the end of the line) or better, use NOT the parasitar modus and spend the power line 100nF at each 18B20.

If this not help, reduce the polling interval.

another idea: each 18B20 has his own task, could it be that there are sometimes conflicts on the bus?

i use here on one esp module 5 pcs, but my software (symcon.de) ignores the resetvalues.

[tozett]

please be so kind an report any progress in getting these multiple 1-wire sensors to work on the espeasy..