Re: Any 1-wire experts around ???

[Stephen McGarry <stephen@xxxxxxxxxxxxx>]

Reading the guidelines from maxim shows your network weight is about
50m so=
Appendix B should apply. So you need to=20
insert a 62 Ohm resistor in the data line and add a small capacitor of
betw=
een 1 and 4.7 nano farads (nF) to ground. I=20
would definitely change to external power as this is more reliable.
Looking=
at the power injector board you should be=20
able to cut the pcb trace for the data line and insert the resistor and
cap=
acitor on the pcb.

HTH
Stephen

On 20/07/12 21:29, Kevin wrote:
>
> I've had a network of 23 1-wire DS18S20 temperature sensors as well as
a =
couple of DS2423 counters running for while=20
> now, talking to Homeseer through the mcs Temps plugin via a DS9097U
seria=
l interface.
>
> It's been OK but I get an increasing error count and the the readings
can=
be 10-15 mins old before they update again=20
> (depending on sensor). They're connected using CAT 5e on a linear bus
app=
rox 40 metres long (23 temperature sensors=20
> and 2 dual counters.)
>
> I've been doing a bit of research into how to optimise the network and
re=
duce the error count but I'm getting more=20
> confused by the conflicting advice. I've variously been advised to:
>
> 1: Move to external vs parasitic power. Not a big move, when I
installed =
the network I used RJ45 sockets with the vdd=20
> shunted to the gnd - easy to remove. I bought a power injector from
Hobby=
boards at the same time as the sensors and=20
> in true HA style it's sat in a box for the last couple of years.
>
> 2: Place a 100-120 ohm resistor between the DQ and the network - not
so e=
asy as it would involve removing each sensor=20
> and resoldering the connections.
>
> I've read the Maxim Guidelines for Reliable Long Line 1-Wire=AE
Networks=
=20
> http://www.maxim-ic.com/app-notes/index.mvp/id/148
but am still none the =
wiser.
>
> So any advice - Resistors a good idea or just for for external power ?
Bo=
th or neither ? anything else ?
>
> Cheers
> Kevin W
>
>
>=20



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