One Wire temp sensor wiring question

[EuBrew]

I will be running 6 probes off the one wire card on my brewtroller in a daisy chain.

Google seems to be all over the place for resistor placement. Does each DS18B20 get a resistor on the power line? Or is it one resistor at the one wire card power. I've also seen the resistor wired across the data and the power line at the one wire card.

In short, where the heck does the resistor go???

Thanks!!

 

[Aerobrew]

You will need a 4.7k pull up resistor tied between the + bus and each of the data legs. It is used to essentially stabilize the data feed. Some newer type of probes may not need it, but i have used them on all my sensors.

Now since it is a pull up resistor you only need to add it to the data side. If you are putting all the sensors on one gpio pin then one resistor will work on that line.

 

[atoughram]

Thats one 4.7K resistor between the + and data leg. One between each of the data legs is not correct, if you add more resistors in parallel, the resistance drops. So, even with six DS18B20's - you only need one resistor.

 

[Aerobrew]

That is correct as long as they are tied together. Think of it as one resistor on one data bus. You can connect multiple probes to the bus with one resistor. If you build 2 data buses you would need a resistor on each bus.

 

[atoughram]