I just got my thermocouple up and running today..
It seems to do the right thing, so that's good. it seems off by a couple
degrees C at room temp, but it's hard to really know :)
it's a TypeJ (Iron/Constantan). The only wierd thing is that the SNS pin works
'right' when the positive lead of the thermocouple is connected to gnd, and the
negative lead to SNS. otherwise it returns neg voltage.
My only concern with it is that i'm running it off my main 5v 1-wire bus, and
the spec says it should be max 4.5v
Works OK so far. I'll eventually throw a couple diodes in i suppose, to lower
the voltage.
you want me to send pictures/schematics in off-list?
Here's it measuring the air just above a candle flame:
$ cat vis
0.00572031
...
$ cat typeJ/temperature
197.026
(measurements were not taken at the same time)
-tmk
----- Original Message -----
From: "Paul Alfille" <[email protected]>
To: "OWFS (One-wire file system) discussion and help"
<[email protected]>
Sent: Wednesday, January 20, 2010 3:52:12 AM GMT -08:00 US/Canada Pacific
Subject: Re: [Owfs-developers] bug in ds2780 (ow_ds2760) code, plus patch
Wonderful, I'll apply the patch. I think you are the first to report on using
OWFS with the DS2780.
By the way, if you have a picture or schematic of your thermocouple, I'd like
to post it on the website.
Paul Alfille
On Wed, Jan 20, 2010 at 1:20 AM, < [email protected] > wrote:
Hi folks,
I was able to find a DS2780 on eBay, and decided to have a go at making my own
thermocouple reader. great fun.
Anyhow, after soldering the tiny TSSOP onto a breakout board, i was afraid i'd
zapped it!
The temperature reading was constantly 0. Other functions worked, voltage, PIO,
etc.
I sucked down the memory, and was able to look at the datasheet and figure that
0x0A and 0x0B held the temperature. To my delight, the temperature was there
and seemed accurate!
OWFS still returned it as 0 though.
I scanned through the code and found the problem. There's a typo which is
making the DS2780 use the memory offset for the DS2760.
here's a patch. Tested and working. This is against owfs-2.7p27, btw.
Cheers, and thanks for a great package.
-tmk
--- broken/module/owlib/src/c/ow_2760.c 2010-01-19 22:11:16.000000000 -0800
+++ module/owlib/src/c/ow_2760.c 2010-01-19 22:05:04.000000000 -0800
@@ -832,7 +832,7 @@
switch (pn->sn[0]) {
case 0x32: //DS2780
case 0x3D: //DS2781
- off = _1W_DS2760_TEMPERATURE;
+ off = _1W_DS2780_TEMPERATURE;
break;
default:
off = _1W_DS2760_TEMPERATURE;
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world's best and brightest in the field, creating opportunities for Conference
attendees to learn about information security's most important issues through
interactions with peers, luminaries and emerging and established companies.
http://p.sf.net/sfu/rsaconf-dev2dev
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