Re: gEDA-user: temperature logger/sensor

[Kipton Moravec <kip@xxxxxxxxxx>]

I probably would have gone with the Atmel Data Flash as opposed to the
memory chips you are using. (But it uses SPI Interface.) For example:
http://www.atmel.com/dyn/resources/prod_documents/doc3500.pdf


As far as the Power Supply goes, replace the 470 pF cap. Either you
accidentally put the wrong on on, or something is bad with the solder
joint. Take what you have off, and put a new one on. Clean the board
with Alcohol if you are using no clean or rosin core solder, or wash it
if you are using water soluble solder flux.

The other problem may be the C101 470 uF capacitor. Usually switchers
need very low ESR capacitors in this position. So two electrolytic in
parallel, or a Low ESR Tant. and add a ceramic 10 uF and 1 uF help
ensure a low ESR with the big cap.  

Kip

On Sun, 2008-11-30 at 18:18 +0100, Levente Kovacs wrote:
> Hi,
> 
> 
> In the last few weeks, I've been busy designing and bulding a temperature
> sensor/logger. The second version is out and can be found here.
> 
> http://logonex.eu/~leva/projects/temp_collector/
> 
> There are a few pictures of it.
> 
> http://logonex.eu/gallery/tns/1043.html
> 
> There is no firmware yet, I am planning to write it in the coming week.
> 
> Originally, I was asked to make some temperature logger, which logs the data
> of samples taken every half 30 minutes in a half of a year. I planned using
> KTY temperature sensors. However, if you change the gain of the INAs you can
> use it with PT100 sensors. I am planning to replace my reflow oven design with
> this circuit. BTW INA. I know that one can buy INA in a single IC, but, AFAIK
> they are quite expensive, and they are too sophisticated for this application.
> 
> It is equipped with I2C eeproms to store the recorded data. The RTC with the
> supercap maintains time and date data even with power supply loss. I am
> thinking to use a battery instead of the supercap.
> 
> The power supply gives me lot's of head scratching. I placed a 470pF capacitor
> to produce the 50kHz switch frequency, but according to my measurements it is
> only 6kHz. I replaced the cap, but stiill the frequency is low. Despite this
> fact, it is working good, and it has only 30mV ripple. If anyone could give me
> a hint what is going on here, that would be fine. In my first sample, I used
> the same circuit, with the same cap, and the frequency was 50kHz. Very odd.
> 
> 
> Cheers,
> 
-- 
Kipton Moravec AE5IB
"Always do right; this will gratify some people and astonish the rest."
--Mark Twain




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user