Index of /dallasharddrive
Hard Driving a Long Chain of DS18B20 Temperature Sensors
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Hard Driving a Long Chain of DS18B20 Temperature Sensors
Richard Lamb
July 2021
To effectively communicate with a large number of Dallas DS18B20 one wire temperature
sensors along a long wire I needed not only 5 volts and 3-pin (vcc,gnd,i/o) operation
but also a higher current driver.
Solved the problem with an old SN74LS241 bidirectional bus driver connected to the
3 volt GPIO ESP8266 pin (running Espurna or whatever). Had to slightly modify the code
to toggle the direction of the '241 (see OneWire.cpp. My mods are "#ifdef RICKTRISTATE").
Schematic, picture of device, and typical installation here:
Yeah, a big cap (330uF) across the USB +5 seemed necessary for the PS I was using.
Draws 100ma@5V but large ripples w/o cap.
I hope this is useful to somebody.
-Rick
References
[1] Maxim Integrated. DS18B20 Programmable Resolution 1-Wire Digital Thermometer. https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf