1-Wire Modules.

[StuartP]

Following on from the 1-Wire thread on the mailling list, I've created a post to allow discussion about purchases of my 1-wire temperature modules.


More pics here: http://bit.ly/c5Rkxj

[SiliconPixel]

Looks good

what controller(s) do you use for your 1-wire? Oh, and what part is the sensor?

Paul.

[StuartP]

what controller(s) do you use for your 1-wire? Oh, and what part is the sensor?

I'm using a USB to 1-wire converter then linux with OWFS, the sensor is a DB18B20 which I recommend is used in powered mode rather than parasitic.

[SiliconPixel]

Thanks Stuart

[bmcomp]

Hi Stuart,

I've always been interested in these 1-wire sensors but never got a round to doing anything with them. I just have a few questions on the module.
I assume these can 'daisy chained' along a network (hence the dual RJ45) and use a usb to 1-wire to read them all on my PC?
Also if I was to use the terminals for an external sensor can it read the external sensor as well as the temp sensor on board or is it just one or the other?
And finally I assume if the on board temp sensor was left off it will work fine with a sensor installed on the terminals?

Oh and would you have any problems posting them to Ireland if i got a few off you?

Cheers
B

now to go and actually do some reading up on 1-wires!

[StuartP]

You are correct the RJ45 connectors simply provide the ability to daisy chain.
You can use both the screw terminals and the onboard sensor at the same time, you can also only use the external sensor if thats a requirement.

No problem with posting to Ireland.

[Simon300]

Schottky diode?

I see that Stuart's PCB has a space for a Schottky diode.

There's a mention on the digitemp site about putting one at the end of the network. I also found it described in Maxim's AN108 MicroLAN In The Long Run which says:
"If it is not possible to stretch the timing, a Schottky diode placed across the bus at the far end is suggested to clamp the inductive generated voltage overshoot. Connect the diode across the cable with the cathode on the data line, and the anode on the return. Only one diode is required for each length of MicroLAN with problem inductance."

How often do people need to add this diode in practice?

[StuartP]

I've stopped using diodes on the end of branches and have had no problems.
Best advice I can give is to not use them, if you start seeing problems then remove the last sensor from the chain.
If removing the last sensor works, try adding the diode to the last sensor and re-instating.

I think in reality, the use of properly terminated cables really makes a difference, and removes the reflections you see with other sorts of cable termination.

[Simon300]

...I think in reality, the use of properly terminated cables really makes a difference, and removes the reflections you see with other sorts of cable termination.

Thanks for the reply Stuart. When you say "properly terminated" you mean only use RJ45 (or RJ11 I suppose) connectors and not, say, plastic electrical terminal strips?

[bmcomp]

Hi Stuart, sent you a PM.

[StuartP]

Ok.

Looks like there's a slight delay on getting DS18B20s.

Anyone else interested in either full kits of parts, or individual bits, let me know.

Once I've got all the bits, I'll update and ask for payment before shipping.

[StuartP]

Ok.
Looks like there's a slight delay on getting DS18B20s.

Ok. Weather strikes, looks like shipment of the RJ45 sockets I need to the supplier has been impacted by the poor weather as well as the DS18B20's.

I'm now NOT expecting items to arrive in time for me to dispatch anything prior to christmas. More news when I get it.

[StuartP]

Ok. No RJ45 connectors, so time to re-order.

Can you confirm your interest buy replying to this thread with details of what you'd like.

For those joining us from twitter, details in the first couple of posts in this thread.

[Simon300]

Can you confirm your interest buy replying to this thread with details of what you'd like.

Stuart

Can you put me down for a couple of complete kits please.

Also how much are the double jacks likely to work out at? I could probably use half a dozen of those for less important sensors and just solder the chip straight on (I've done that with an RJ45 coupler but it is pretty fiddly!).

Thanks!


Simon

[Simon300]

I might be interested in the jacks (and maybe boards) for this little possible project too:

http://www.navitron.org.uk/forum/index.php/topic,12588.msg142872.html#msg142872

I'll see what happens in the next day or two.

Simon