Leaf Wetness

[epierre]

From this document here is the caracteristic of the leaf wetness response to events:

[epierre]

I'll try to power a 3.3V mini pro with a 3xAA batteries holders, and have it lowered to 3.3V with an AMS1117.

Sensor resistance seems to lower when there is humidit on the holder as expected. I have 735 as analogRead when it is dry.

[epierre]

First test yesterday, device is well powered, device presentation ok, but afterward nothing was mesured... to be investigated on connexions...

[epierre]

hmmm... difficult to make it work on batteries... AND the gas sensors overloading the radio.... now I have it functional.

[RJ_Make]

@epierre

What do you mean the gas sensor overloaded the radio?

[epierre]

@ServiceXp just that I have a Mega sketch with 7 sensors reporting too frequently one one side, and on the other the weservice call was too slow, making me think of no transmission, but it was delayed in fact...

[epierre]

Some experiments:

• I left it on a window border, it varied by one ohm on the night.
• radio close is ok with the basic antenna.
• i'll try to see to put it further outside, at the moment there are more than 10°C difference along with wet cars on the morning. I fear the rain drop may not be enough sensible...

There is an alternative to the expensive davis one: LEAF WETNESS SENSOR

I'll modify the sketch to report a percentage, as other humidity sensors would do.

Some interresting discussion:

• 200 KOmhs = very dry leaf
• 20 KOmhs = slew fog
• 5 KOhms = heavy rain

About oxydation, dfrobot has one ground probe with this explanation:

Immersion Gold which protects the nickel from oxidation. Electroless nickel immersion gold (ENIG) has several advantages over more conventional (and cheaper) surface platings such as HASL (solder)

[epierre]

some returns:

• from Sept 11th to 15th, the batteries (3*1.5V) went from 4.5V to 3.2 as mesured today, it stopped emitting on sept 15th
• the leaf sensor shows heavy signs of oxydation without any rain during the period... this is a real problem with all those copies around... that is not a very viable solution...
  

I've seen another product from Spain at Liebllium that I guess I will test for I haven't found any other item...

[Yveaux]

@epierre said:

heavy signs of oxydation

You're definitely not the first to report this.... I've read many negative reviews of these cheap sensors.

[epierre]

@Yveaux but finding good one seems to be .... very difficult... I've spoken of immersive gold... will try to see if those are better....

[Yveaux]

@epierre any idea why your sensor lasted this short?
How often did it report its value to the gateway? Was it sleeping in between? Any other sensors connected?

[epierre]

@Yveaux several ideas:

• it reported every 10000
• it has no other sensor (this was my first try on batteries...)
• I had an AMS1117 in entry but I didn't needed it
• I haven't hacked the 3.3V core with the websites @a-lurker ideas

I'm waiting for the batteries from my other post because using so fast batteries is not environment friendly...

Has there been simulation of energy usage for those arduini ? e.g. for a spark core it isadvertized at 500mW

[epierre]

I've finally received from cooking hacks the leaf wetness sensor board that should be better than the one from china...

It is the one from hobby boards:

I guess I can recycle the lectronic from the cheap one on this one ?

[hek]

It doesn't look much different that the china-ones. Is it gold-plated or something?

[epierre]

yes it is, from the hobby board site it is $2, but it is a quarter the china's size.

sorry I missed your point, it is gold plated, immersion gold.

[epierre]

Ok, so I made some adjustments from my last try:

• hobbyboard immersion gold sensor
• I kept the comparator from the other sensor to facilitate work with the arduino
• I've added a 18650 LiOn battery (5000mAh) to have an extended life cycle

Here is the sketch:
https://github.com/empierre/arduino/blob/master/LeafWetnessSensor.ino

What I can say, is that it is very sensitive. It is now outside live in the cold.

This could be used for a leak sensor easily.

[epierre]

so my 5000mAh lasted outside... 4 days... btw I didn't remove all leds from the comparator that could be an improvement and the outside weather is quite cold.

I had a reading every 30 secs, way to quick surely...

@hek is there a way to power the radio only when necessary ? I guess the gw.sleep could be a gw.sleep and a gw.wakeup and manage the delay outside ?

[hek]

@epierre

gw.sleep() sleeps the radio as well. What do you mean by power down radio? Like cutting power using digital pin?

[epierre]

@hek said:

@epierre

gw.sleep() sleeps the radio as well. What do you mean by power down radio? Like cutting power using digital pin?
yes, now you combine sleep for the radio and delay, what I mean is to have loop() run without radio, and if a transmission is needed to have a command that power it.

If you have a long dry period, a device on battery will consume a lot of power having the radion on and off, if it is always off until a sensor finds something, that would save more power, no ?

[RJ_Make]

Wake only on interrupt?