1-Wire Sensors

[SirMaple]

I'm having issues connecting DS18B20 1-wire sensors to my GEM.

I'm able to get 1 to work but when I go to add the next it doesn't work.

How do I add 8 of them to the GEM?

Do I only connect 1 at any given time when adding them?

Tried looking for a step by step guide but couldn't find one.

Any help would be greatly appreciated.

[Teken]

I'm having issues connecting DS18B20 1-wire sensors to my GEM.

I'm able to get 1 to work but when I go to add the next it doesn't work.

How do I add 8 of them to the GEM?

Do I only connect 1 at any given time when adding them?

Tried looking for a step by step guide but couldn't find one.

Any help would be greatly appreciated.

Yes, enroll one sensor at a time once done you can wire them all to the network.

[ben]

I recall some customers needing to use a strong pullup resistor when wiring multiple DS18B20s. Take a look at Maxims notes here: https://www.maximintegrated.com/en/app- ... mvp/id/148

[SirMaple]

Is it possible to somehow get the ROM code in linux? I have them all connected to a raspberry pi right now.

It's an extreme pain to remove some of my sensors so I can hook them directly to the GEM one at a time.

[ben]

Is it possible to somehow get the ROM code in linux? I have them all connected to a raspberry pi right now.

It's an extreme pain to remove some of my sensors so I can hook them directly to the GEM one at a time.

There's guides for the RPi, such as this one you can try:

http://www.modmypi.com/blog/ds18b20-one ... spberry-pi

for 1-wire sensors.

[ben]

The GEM can also scan/save all sensor codes, but you might have an issue if there's any problem with communication.

[gosmond]

Separate question about 1-Wire sensors --

What is the maximum supported bus length for attaching up to 8 sensors?

In my situation I would like to have a bus length somewhere between 100 and 200 feet total, with sensors spaced anywhere from 10 to 30 feet apart along the bus.

Is that going to work? WIll it help if I use UTP (twisted pair, 24-AWG) cable? Pull up resistor?

Assume for this scenario all brand-new wire with well-made connections, in a relatively low noise residential environment.

[ben]

Separate question about 1-Wire sensors --

What is the maximum supported bus length for attaching up to 8 sensors?

In my situation I would like to have a bus length somewhere between 100 and 200 feet total, with sensors spaced anywhere from 10 to 30 feet apart along the bus.

Is that going to work? WIll it help if I use UTP (twisted pair, 24-AWG) cable? Pull up resistor?

Assume for this scenario all brand-new wire with well-made connections, in a relatively low noise residential environment.

This is something we unfortunately can't really know as it's very environment dependent.

I would read up on the Maxim guide here: https://www.maximintegrated.com/en/app- ... mvp/id/148.

Definitely use twisted-pair, shielded cable as it'll help with filtering out any noise.

If I remember correctly, Teken has some pretty long runs, he might be able to give some advice.

[Teken]

Key things in no specific order of importance for a successful and reliable 1 wire network is the following.

1. Use high quality 1 wire sensors and don't purchase them based on price alone. Brultech sells 1 wire sensors at a reasonable price so that is an option for those not wanting to take a chance on quality. I was very fortunate that I purchased cheap and reliable sensors on EBAY. But also have to affirm one batch I purchased were less than stellar.

2. Wire Diameter: is important if long runs are going to be seen. So if you intend to use Ethernet cable I would suggest you pay extra and use CAT-6 wire. Its important to note this wire comes in both 24 vs 23 AWG diameter.

Please use 23 AWG wire and it must be pure solid copper and not CCA (Copper Clad Aluminum) as its not in wall rated or NEC / CEC approved. Ideally you should purchase 22-4 alarm wire as its thicker but offers no shielding if that is required. Using shielded Ethernet cable is a must for noisy environments and must be grounded on one end.

3. Topology: If you read the Maxim white paper it describes the pros / cons of each topology and how it will add *Weight* to the network. In basic English if you have uneven runs or long runs a star topology may impact the system.

4. Noise: Do not run any 1 wire cabling in parallel to 120 / 240 VAC wiring. Doing so will cause untold grief when random loads are called to duty and you won't be able to track it because these loads are intermittent / seasonal etc.

5. Termination: Always use the best termination possible from soldering to field proven crimps.

I have two separate 1 wire networks in my home and one of them spans more than one mile. The GEM spans more than 500 feet so believe you will be more than fine for your short run. I haven't personally had to use a pull up resistor on my network at all.

My ongoing installation thread offers lots of insight and pictures of my 1 wire network so take a look in my signature. Lastly, I used fully encapsulated SS probes as it offered me easy install and long term reliability.

Last but not least if you use the probe style like I did please consider using some kind of isolation material like a rubber O ring / gasket. This will decouple as best as possible the material its installed into vs wanting to measure the temperature of interest.

For direct contact areas like pipes I used Arctic Silver thermal compound and aluminum HVAC tape to make a solid and intimate bond.

[gosmond]

Key things in no specific order of importance for a successful and reliable 1 wire network is the following.
....

Fantastic reply, thank you.

In fact I am thoroughly familiar with the 1-wire specs, network topologies, etc, and aware that distances of 1000 feet and more are easily possible. I just wanted to verify that the GEM implementation of 1-Wire is compliant and not (as far as distance goes) limited or hobbled to a shorter length for some reason.

Speaking of hobbling -- there is a great deal more potential in 1Wire integration if
A) MORE devices can be included, i.e. say 20 to as many as 100. (As I've seen on other 1Wire host devices, such as the HA7NET & OWSERVER devices from Embedded Data Systems)
B) A wider variety of 1Wire devices can be included, e.g. light/dark, humidity, pressure, switch contacts, etc.

In older forum threads here I've seen people request more temp sensors, and also saw the reply from Brultech that it's possible, perhaps, but not a high priority.

As a person who is considering (but hasn't yet purchased) a GEM kit, part of what has me on the fence is that as things stand, to meet my 1Wire temp-reading needs I will probably have to buy a separate HA7NET and/or OWSERVER 1Wire host to get the number of sensors I require. It would be a big incentive to buy if the GEM supported 25+ 1Wire temp. sensors.

Any comment from Brultech on that?