RE: Dallas temp sensors

["Jon Whiten" <jon@xxxxxxx>]

Just to add to hat has already been said.

The pins on the Dallas part are Ground -- Data -- Vdd.  When using
in
Parasite power mode (i.e. driven from the 1-wire bus only) Ground and
Vdd
should be connected together and connected to ground of the RJ11 
Data
should go to Data.

Secondly, are these the DS18S02?  If so, then there is some error
checking
on-board that, when an error is detected, the device reports a temp of
+85C.
Your software will therefore need to interpret this accordingly.

Additional sensors are wired in parallel on the bus but it has been
recommended that a Schottky diode is added across the bus (at the sensor
I
believe) to prevent bus undershoot.  I have not got around to doing
this yet
despite obtaining the diodes 2 years ago!

Regards,

Jon
http://www.whiten.co.uk/



> -----Original Message-----
> From: Paul Gordon [mailto:paul_gordon@xxxxxxx]
> Sent: 19 July 2002 09:05
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Dallas temp sensors
>
>
> Hi Neil,
>
>
> >
> >I cut up a modem lead leaving an RJ11 on one end.....
> >
>
> Good stuff, that's what I planned to do...
>
>
> >The pins are as follows looking at the rj11 connector with the
> clip facing
> >up....
> >
>
> Would that be with the clip facing up, _and_ the cable entry end
facing
> towards you, and the contact end facing away?....
>
>
> >Assuming pin 1 is on the left
> >
> >PIN 1 = Not connected
> >PIN 2 = Ground (Green on my cable)
> >PIN 3 = DATA (Red on my cable)
> >PIN 4 = Not connected
> >
> >To connect to the temp sensor, assuming the flat side is facing
up
> >PIN 3 (Data) connects to the middle pin
> >PIN 2 (Ground) connects to the Left pin.
> >
>
> Would that be with the flat side facing up _and_ the legs
> pointing towards
> you?...
>
> And the 3rd leg on the 1820 is unused then?...
>
> Cheers.
>
> Paul G.
>
>

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