1 Wire pull up resistor

5 replies [Last post]
Joined: 7 Mar 2012

Can someone clear something up for me with regards the pull up resistors on the temp sensors.

Do I need to use 1 pull up resistor per sensor IC, or is it just 1 pull up resistor for the whole array?

Providence, United States
Joined: 9 Jan 2010
That's an easy one.  One pull

That's an easy one.  One pull up resistor per 1-wire bus.   As only 1 bus is provided you need but 1 resistor.

Its value well there is another discussion right there.  It can move around depending on the length and number of devices on your bus.

Joined: 7 Mar 2012
Thanks Brett,The next

Thanks Brett,

The next question is does it matter where it is located along the bus?

Tallinn, Estonia
Joined: 2 Mar 2011
Exact values and location

depend on cabling type, length and quality.  Main target here like I was teached by Derek is to have pullup resistors close to sensors.

E.g. one of the configurations working for me:
- six sensors, cat5 cabling, total length around 100m
- connections are star-like, each sensor on a separate leg
- resistors soldered to sensors are 2k7, 2k4, 6k8, 6k8, 2k7, 1k6 (smaller values for longer legs)
- total resistance is around 480 ohms that is close to limit (maybe over already in some other setup)


Joined: 7 Mar 2012
Hi Aivo,This is in conflict

Hi Aivo,

This is in conflict with Brett's update.

You state having 1 resistor per sensor, but Brett advises that only 1 resistor per bus is required!

United Kingdom
Joined: 31 Mar 2011
It about total resistance

Lawrence. It's not about number of resistors it's about total resistance and bus type. For an unusual and star shape bus individual resistors at each sensor seems to work best for a simple bus 1 resistor will be fine It's a case of trial and error I find! Thanks Garry

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