user41638: I'm attempting to connect 6 DS18B20 temperature sensors to an Arduino GPIO pin in a topology that looks something like this:

Conceptually, it's a star network with two star subnets.
The GPIO pin on the Arduino is connected to point "E" through a 4-inch wire, a JST connector, and another 4-inch wire.
The 3 wires (shown in green) connecting sensors "A", "B", and "C" to point "D" are approximately 3 feet long (and are, in fact, the original ~1-meter wires that came pre-attached to the sensors when I bought them). Segment ED is ~4 feet long.
The 3 wires (shown in blue) connecting sensors "G", "H", and "I" to point "F" are approximately 20-30 feet long (including the original 3-foot wires attached to the sensors when I bought them). Segment EF is ~8 feet long.
No parasitic power is involved. Every DS18b20 has 3 wires... +5v (probably closer to 4.5v by the time it gets to G/H/I), ground, and 1-wire data.
So... where would YOU recommend putting resistors (feel free to describe points besides the ones I labeled with letters), and what values would you use?
And... would it actually be any better to take advantage of the fourth (presently unused) wire in the cables I have connecting G, H, and I to F as a 'return wire' to turn it into a much longer daisy chain (E to F, F to G, G back to F, F to H, H back to F, F to I), or something even more radical (say, ED, DA, AD, DB, BD, DC, CD, DE, then continuing the daisy chain with EF as described previously)?
For what it's worth, I presently have a single 4.7k pullup resistor sitting at point "E", and it seems to work... but after reading Maxim's AppNote about "Building reliable long 1-wire networks" (Appnote 148), I'm feeling like it shouldn't work, and that I really ought to do something more sophisticated for the sake of long-term reliability.

user313: I have a linear network with three thermos at roughly 5', 20', and 40-50' from the micro (a 5v '328p), as well as being parasitically powered. The physical bus is a twisted pair from a Cat-5 cable. The pullup is 4.7KOhm on the processor board.
I've tested this network using a 3.3v '328p and it wasn't as reliable, but reducing the pullup to 2.2K (IIRC) fixed it.
I find Maxim's App Note 148, "Guidelines for Reliable 1-Wire Networks" to be very helpful and is my go-to for 1-wire network questions.

41638: <p>I'm attempting to connect 6 DS18B20 temperature sensors to an Arduino GPIO pin in a topology that looks something like this:</p>
<p><a href="https://i.stack.imgur.com/o0JZE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o0JZE.png" alt="enter image description here" /></a></p>
<p>Conceptually, it's a star network with two star subnets.</p>
<p>The GPIO pin on the Arduino is connected to point &quot;E&quot; through a 4-inch wire, a JST connector, and another 4-inch wire.</p>
<p>The 3 wires (shown in green) connecting sensors &quot;A&quot;, &quot;B&quot;, and &quot;C&quot; to point &quot;D&quot; are approximately 3 feet long (and are, in fact, the original ~1-meter wires that came pre-attached to the sensors when I bought them). Segment ED is ~4 feet long.</p>
<p>The 3 wires (shown in blue) connecting sensors &quot;G&quot;, &quot;H&quot;, and &quot;I&quot; to point &quot;F&quot; are approximately 20-30 feet long (including the original 3-foot wires attached to the sensors when I bought them). Segment EF is ~8 feet long.</p>
<p>No parasitic power is involved. Every DS18b20 has 3 wires... +5v (probably closer to 4.5v by the time it gets to G/H/I), ground, and 1-wire data.</p>
<h4>So... where would YOU recommend putting resistors (feel free to describe points besides the ones I labeled with letters), and what values would you use?</h4>
<p>And... would it actually be any <em>better</em> to take advantage of the fourth (presently unused) wire in the cables I have connecting G, H, and I to F as a 'return wire' to turn it into a much longer daisy chain (E to F, F to G, G back to F, F to H, H back to F, F to I), or something even more radical (say, ED, DA, AD, DB, BD, DC, CD, DE, then continuing the daisy chain with EF as described previously)?</p>
<p>For what it's worth, I presently have a single 4.7k pullup resistor sitting at point &quot;E&quot;, and it seems to work... but after reading Maxim's AppNote about <a href="https://pdfserv.maximintegrated.com/en/an/AN148.pdf" rel="nofollow noreferrer">&quot;Building reliable long 1-wire networks&quot; (Appnote 148)</a>, I'm feeling like it <em>shouldn't</em> work, and that I really <em>ought</em> to do something more sophisticated for the sake of long-term reliability.</p>
 313: <p>I have a linear network with three thermos at roughly 5', 20', and 40-50' from the micro (a 5v '328p), as well as being parasitically powered. The physical bus is a twisted pair from a Cat-5 cable. The pullup is 4.7KOhm on the processor board.</p>
<p>I've tested this network using a 3.3v '328p and it wasn't as reliable, but reducing the pullup to 2.2K (IIRC) fixed it.</p>
<p>I find Maxim's App Note 148, &quot;<a href="https://pdfserv.maximintegrated.com/en/an/AN148.pdf" rel="nofollow noreferrer">Guidelines for Reliable 1-Wire Networks</a>&quot; to be very helpful and is my go-to for 1-wire network questions.</p>
