Go Down

Topic: Yun and TMP36 strange behavior (Read 1 time) previous topic - next topic

aboudou

Hello everybody,

I've setup an Arduino Yun to provide the following graphs :
- ambient light, with a photo resistor and a voltage divider, which work well : http://malheur.goddess-gate.com/light/
- ambient temperature, with a TMP36 sensor, which has a strange behavior : http://malheur.goddess-gate.com/temp/

As you may see, there is a regular temperature / voltage drop which happens every 31/32 hours, and I can't explain it, and this voltage drop only happens with temperature measure, not light measure.

The photoresistor and TMP36 are powered by the same +5V pin, photoresistor output is measured with A0 pin, and TMP36 with A1 pin. There's a 100 µF capacitor near VCC and GND pins of the TMP36 sensor.

Light and temperature values are gathered every 10 minutes by a cron job on Linux side via a REST query. Arduino sketch just wait for the REST query and return A0 and A1 values. Temperature measurement is not a single shot : when temperature is asked, I take 10 measure each 1 second, then return the median value.

I can't really explain :
- Why the voltage drop
- Why it only happens to temp measure
- Why it happens regularly, every 31/32 hours.

If someone here have an idea, (s)he's welcome :-)

Thanks
https://goddess-gate.com/
http://raspberrypi.goddess-gate.com/
https://twitter.com/boudouarnaud
http://www.fablab-sud31.fr/

thombrooks

I'm sorry I don't have an idea on how to help you with your problem, but would you mind if I asked you how you made sure that cron is running when the board boots up?

I have created a crontab entry, but don't see cron in the ps (process) list. I can see a script for it in /etc/init.d which is linked from /etc/rc.d .... 

HANG ON!

I love answering my own question:

found here, http://wiki.samat.org/CheatSheet/OpenWrt

/etc/init.d/cron enable
/etc/init.d/cron start

Now hopefully the next person to google this will find the answer quicker.   :)

Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy