This guide about the DS18B20 says a 4,7 k ohm pullup resistor should be used between the 5V power source and the signal pin. The sensor can also operate at 3.3V, but do I have to use another pullup resistor at this voltage to get the correct readings?
The data sheet does not say anything about changing the pullup based on voltage. It only says about 5K - see page 10
https://www.analog.com/media/en/technical-documentation/data-sheets/DS18B20.pdf
If you do the math that works out to about 1mA on a 5 volt system. I use 1mA as my starting current and about 3mA as the max depending on the devices on the bus. The more items on the bus the more current is required. I use a scope to be sure the rise and fall times are within range.
Here are the specifications:
| Power Supply | 3V to 5.5V |
|---|---|
| Current Consumption | 1mA |
Since it spec's 1mA I'd suggest using a 3k3 pullup
See figures 6 and 7 in the data sheet.
if using parasite power, you will need more than a pullup resisor.
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.