circuit humidity sensor

Archiver

Hi Dr Patel,

This is very much like the hysteresis topic discussed a few days ago.
The main program loop could be something as

drylimit con 5000 'example values
wetlimit con 25000
pin_relay con 2 'relay controlled by P2
hum var word

Mainloop:

gosub readhumidity 'get reading from humiditysensor into variable hum
if hum < drylimit then relay_on 'turn realy on to start watering plants
if hum > wetlimit then relay_off 'turn relay off to stop watering plants
goto mainloop 'keep checking hymidity while relay is on or off

readhumidity:
hum = input from sensor 'code depends on sensor
return

relay_on
out pin_relay,1
return

relay_off:
out pin_relay,0
return

end

This is just a global layout. You could also use a single limit value (too
dry) and
then start watering for a fixed amount of time. In that case a simpler
sensor may be
used (if available).

For sensors take a look at http://www.smartec.nl/index.htm?/smart3.htm
It describes a Univeral Transducer Interface (called UTI) with RS232 in/out
and connects
to all kinds of sensors, including temperature and humidity.
Or download their application note directly
http://www.smartec.nl/pdf/apputi01.pdf

Hope this helps.
Success.

Greetings peter