rjnusbaum:
I've wired it up 3 or 4 different ways on two different breadboards. Same result. Any 4 sensors works fine. Add any 5th sensor and they all disappear.
Solved. Was using 4.7k pullup resistor as recommended. Too big for 5 sensors as when they all pull power during conversion they drop voltage below minimum. 1k resistor seems to make things work.
I rather suspect something else is going on. Reducing the pullup is common practice when using long cable runs to the sensor, which is probably not the case here, and even in that situation, 2.2k is about as low as I have ever heard of.
Nick_Pyner:
I rather suspect something else is going on. Reducing the pullup is common practice when using long cable runs to the sensor, which is probably not the case here, and even in that situation, 2.2k is about as low as I have ever heard of.
If there is I haven't figured it out. The sensors I am using are the waterproof ones with the 3' cables. I have tried a bunch of different wiring configurations on two different breadboards. I tried 3.3V and 5V (both of which should work). I then tried the resistor change. 2K made the sensors appear to a scan but would not work reliably when actually getting the temp. 1K makes everything work.
I have not found a single example documented online that used more than 4 sensors on a single bus. It definitely should work but I haven't figured out why it isn't. Oh and I have tried both a UNO and a Mega board. I am going to try them with my Pi too and see what happens there.
I can't comment other than that I hope you aren't using the parasitic power mode. I only use four at a time myself, all waterproof 3m, but there have been instances on this forum of people using more, and with no problem. Using waterproof sensors with cabling means you have gotten round one DS18B20 problem - using cheapskate cabling. The type of sensor per se is irrelevant, and the only issue that might come up with Arduino is whether it is 5v or 3.3v, which is not relevant here. I believe the sensor only uses the pullup when it is actually passing data, which rather suggests that the number of sensors has no bearing on the size of the pullup. I think this is one for el Supremo, who is rather supreme on these matters..
Nick_Pyner:
I can't comment other than that I hope you aren't using the parasitic power mode. I only use four at a time myself, all waterproof 3m, but there have been instances on this forum of people using more, and with no problem. Using waterproof sensors with cabling means you have gotten round one DS18B20 problem - using cheapskate cabling. The type of sensor per se is irrelevant, and the only issue that might come up with Arduino is whether it is 5v or 3.3v, which is not relevant here. I believe the sensor only uses the pullup when it is actually passing data, which rather suggests that the number of sensors has no bearing on the size of the pullup. I think this is one for el Supremo, who is rather supreme on these matters..
Nope not using parasitic power mode.
Good - and at least you have something that works. I guess the how can wait, and that will show up eventually.
I love these sensors with only one exception. Each sensor has its own ID and I have a project that has 60+ sensors in a chain. There are destined to be 10 chains so thats some 600 sensors. lol... luckily each chain has its own ESP. however that a lot of sensors and once the chains are built I then need to record the ID of each and every sensor 
At present I am deciding if I should store the ID on the Arduino in a table and assign a number to it from top to bottom so as to reduce the logging overhead. To make life even harder the supplier has not supplied the sensors on a strip so the numbering is not incremental.
There is a small temptation to write a routine that allows me to sort the sensors so when they are installed they can be inserted in the chain from the lowest number to the highest.
Any one else have any great ideas as to how to handle this?
Oh and to make matters more interesting when the units are deployed if they cant fit all the sensors they will just cut off the excess so a chain may end up truncated to between 30 ~ 60 sensors then the excess will be used on the next chain.
vangalvin:
I love these sensors with only one exception. Each sensor has its own IDAny one else have any great ideas as to how to handle this?
One possibility is that you start with coming to terms with the individual addresses being more an asset than a liabilty.
Nick_Pyner:
One possibility is that you start with coming to terms with the individual addresses being more an asset than a liabilty.
lol. there are up to 30 chains being deployed in this project. The big bonus is that recording each one's ID is going to allow for quility control at the same time 
Okay, I got the principal of setting multiple Dallas DS18b20 up with my Arduino. Now my question: how can I Display the readings on my pc in a drawing of the Sensor location?
Info: this is for 8 geothermal wells, 100 m deep, one sensor every 10 m =168 (one at the bottom, then one on every leg, cold & warm pipe)
Thanks, Joerg
kslfarms:
Okay, I got the principal of setting multiple Dallas DS18b20 up with my Arduino. Now my question: how can I Display the readings on my pc in a drawing of the Sensor location?
By paying somebody a motza to write a graphics programme that does this. It may be doable in HTML, or even Excel. The gigs and collaboration forum may be worth a look.