External Power Supply on RF 315/433 MHz Transmitter-receiver Module

I just tried to find one on the internet but no luck so far. The name of this sensor is the YL-69.

But the analog pin can deliver 5V too?

Edit: I found this doc : http://eie.uonbi.ac.ke/sites/default/files/cae/engineering/eie/MICROCONTROLLER-BASED%20IRRIGATION%20SYSTEM.pdf

It says 35 mA. Should I use a transistor to give more current ?

alex52:
I just tried to find one on the internet but no luck so far. The name of this sensor is the YL-69.

But the analog pin deliver 5V?

Why would you use an analogue output? A digital pin supplies 5V. (Absolute maximum 40mA, so up to about 30mA would be fine. (I'm assuming that the sensor needs a 5V supply voltage.)
You just need to ascertain how much current the sensor uses. You could use a 1Ω to 10Ω resistor in series between the +5V and the sensor's Vcc pin, then measure the voltage developed across it to determine the sensor's current consumption. I = V / R

Edit: Where did you buy the YL-69? They might have the specs.

I just got a diagram for the YL-69, (attached). I expected an analogue output, but it looks like a digital output, set around an adjustable threshold.
If your's is the same, (using an LM393 comparator, and with two LEDs), you will be fine to use an Arduino digital pin to power the module via it's Vcc connection.

It has two LEDs, but they have 1K series resistors, so will only use roughly 3mA each. The rest of the circuit uses negligible current.

YL-69 Circuit.JPG

Oups, yes Steve I meant the digital pin, I didn't know it supplies 5V. I've edited my previous message, I found a source. I bought it in the chinese market directly at a small shop ^^

I'm not sure its the same, mine has a comparator with VCC, GND, Analog and Digital output (Same than the one on the doc I've posted)

alex52:
Oups, yes Steve I meant the digital pin, I didn't know it supplies 5V. I've edited my previous message, I found a source. I bought it in the chinese market directly at a small shop ^^

And yes my sensor is the same with the comparator

Good, no problem then. Use one digital pin as an output to power it, and another configured as an input to receive the sensor's digital output.

You edited your reply and now say your's is different. This is getting confusing.

I see, you also went back and edited an earlier post to include a link to the 56-page pdf document of someone else's project. I'm not interested in searching through that to find information.

Just measure the current consumption of your module. If it uses 30mA or less, use a digital pin as suggested to power it, then an analogue or digital pin to read it's output, depending on which you want.

I can't see how it could be damaged as you claim, by keeping it permanently powered.

Yes, sorry... I bought exactly the same than this one in the tutorial : http://www.instructables.com/id/Soil-Moisture-Sensor/?ALLSTEPS

I'm new to this, I'm a bit confused too, I've started recently.

alex52:
Yes, sorry... I bought exactly the same than this one in the tutorial : http://www.instructables.com/id/Soil-Moisture-Sensor/?ALLSTEPS

I'm new to this, I'm a bit confused too, I've started recently.

You keep sending me to read other people's projects. I can answer simple questions, but don't have the time to do an in-depth study. Just do as I suggested in my last reply. That's the best solution.

It could be damaged by corrosion, that's what I've seen a lot in other projects, a lot of people advice to do that from what I've seen.

Ok, I see, thanks a lot for your help! I'll try what you said :slight_smile:

Sorry for the bothering OldSteve. I'm trying my best on this!

alex52:
It could be damaged by corrosion, that's what I've seen a lot in other projects, a lot of people advice to do that from what I've seen.

Right, I guess that's possible, from electrolysis.

I'll try what you said :slight_smile:

That's the best thing. Only takes 1 minute, and then you know exactly how much current it uses.
More than likely it will be under 30mA, but better to be sure than sorry. :slight_smile:

(I don't have a lot of time right now because I'm working on my project, preparing to make some PCBs. I need to get two PCBs made, then drilled and assembled today ready to use tomorrow. That's why I couldn't read the pdf document and go through the instructable you linked.)

If you keep the sensor powered all the time, it will be destroyed in under a month.
I learned that from experience. :confused:

Whandall:
If you keep the sensor powered all the time, it will be destroyed in under a month.
I learned that from experience. :confused:

Whandall:
If you keep the sensor powered all the time, it will be destroyed in under a month.
I learned that from experience. :confused:

That quickly!
A good argument, then, for only powering it when needed. When Alex first mentioned damage if the unit was left powered, I was thinking in terms of the circuitry, hence my comments. Completely overlooked electrolysis. :frowning:

I saved the destroyed headers, but I could not find them right now to show you the remains.

After less than a month only the pcb remained, the copper including plating was gone.

Whandall:
I saved the destroyed headers, but I could not find them right now to show you the remains.

After less than a month only the pcb remained, the copper including plating was gone.

Ah right, I hadn't realised the probes were just normal copper-clad PCB. (I just had a close look at the pic that Alex posted, and his is the same.) Knowing that, I can see how the life would be short. I've seen electrolysis used for etching PCBs, too, and it's fairly fast. I forget exactly what voltage was used, but I have the circuit here somewhere in my magazine collection.

I guess that something more substantial would be better for the probes, then, especially if it was to be continually powered. Short lengths of copper rod, maybe, like the rod that's driven into the ground for an electrical earth rod.

Platinum, gold, nickel or stainless steel would be much better than tin plated copper, or a copper wire.

The dissolved copper could probably even damage the plant you are monitoring.

My bonsai survived one dissolved sensor as yet. :wink:

Whandall:
The dissolved copper could probably even damage the plant you are monitoring.

Possibly, if enough sensors were dissolved into the soil, but I think that many plants are reasonably tolerant to copper, since it's sold as a fungicide for use on plants:-

ACTIVE CONSTITUENT: 93g/L COPPER (Cu) present as Copper Ammonium Complex

Whandall:
Platinum, gold, nickel or stainless steel would be much better than tin plated copper, or a copper wire.

Sad that all they'd need to do is spring for ENIG and the sensors would stop destroying themselves...

DrAzzy:
Sad that all they'd need to do is spring for ENIG and the sensors would stop destroying themselves...

I thought about that, but wouldn't such a thin layer scratch easily when pushed into and removed from the soil a few times, especially if there were sharp, hard pebbles, then begin to corrode from the scratches?

I think you can do moisture sensing by measuring capacitance. Then you don't have to expose metals to the soil.

aarg:
I think you can do moisture sensing by measuring capacitance. Then you don't have to expose metals to the soil.

But doesn't something metallic still have to be in contact with the soil to measure capacitance?