Problem with an array of soil moisture sensors

hi all!

I have four of this soil moisture sensors: http://www.dx.com/p/soil-humidity-moisture-detection-sensor-module-blue-black-white-200142#.U9lkrfkhCbg Individually they work perfect. However, i wired all of them to the arduino board to have readings from different points of the garden.

I have a peace of breadboard with the electronics connected ones near the others, connected to the sensors. Then, a 6-wires cable send the power and signal to the arduino. This cable only use one 5v and one GND wires to power the four sensors. At the breadboard, all the 5V pins are wired together, and the GND too. But each out signal from the devices goes to a different signal wire in the cable.

The problem i detected is that the third sensor in the array does not returns "high" when iput it into water (for test purposes), EXCEPT is any of the others sensors also shows a "high". I don´t know if you see what i mean. If i put only sensor 1 into the water, the ligh of the board turn on. If i repeat this action for the other sensors, one by one, all of them works well except the third in the array. If i repeat the experiment but with two sensors inthe water each time, the third sensors also returns "high" when i put it into the water together with any other sensor...

I checked the wiring and the sensors (changing the sensor from one board to the other), and i have the same behavior.

There is not a code problem, because the board of the sensor works independently of arduino or any other device.

Do you imagine what could be the problem? Thanks!

P.D. I am out of home and i am not hable to post a picture of the wiring, buti think i explained correctly

The problem is probbly a miss match between how you think it is wired and how it is actually wired. A schematic is invaluable first and then a photograph.

Okay, these are the pictures from the entire device, the up and down sides of the breadboard.. https://www.dropbox.com/s/i4z9ifnbh5aclqs/SensorsArray.zip 10Mb!

I will prepare something like a wiring diagram with powerpoint in some minutes..

This is a quick diagram of how it is wired: https://www.dropbox.com/s/bipnak3n31ac5rp/SensorsArray-wiring.jpg

The device with problems is sensor 3 in the diagram, (sensor 1 in the pictures of the real world)

Swap just the sensor. Does the fault follow the sensor if so you have a faulty sensor. If not then you have faulty wiring or a faulty arduino.

Thanks,

As i sayd, I changed the sensors, and the problem remains only in same device, independtly of which sensor is connected to it. And i checed the wiring and it is correct.

As i said, the arduino is not a problem, because it only powers the devices, but i am not checing any code. I sayd the devices are independat or arduino or any other microcontroler to work, it justonly need power.

This is way i am coming crazy with this problem. Thanks

Okay, these are the pictures from the entire device, the up and down sides of the breadboard.. https://www.dropbox.com/s/i4z9ifnbh5aclqs/SensorsArray.zip 10Mb!

Please read the how to use the forum sticky, 10M for a picture is just plain stupid. Resize it so that it is no more that 1000 pixels wide and post it.

I changed the sensors, and the problem remains only in same device,

OK so it stays at the current position so it is the wiring or the arduino.

And i checed the wiring and it is correct.

the arduino is not a problem,

A little story, a girl goes to the doctors and the doctor examines her and says, well I have some good news for your husband. She says "but I am not married". "Then" he said, "I have some bad news for your boyfriend". She says "but I I have not got a boyfriend and I have never had one".

At this point the doctor rushes to the window and opens it and gases out. "What are you doing" she said. The Doctor replied "well the last time this happen a large star appeared in the east."

Moral - you are either mistaken or you have a miracle on your hands.

Thanks for your comments.

However, i said, that i am out of home, and i am so limited on connection time and computer access. This is why the images didn´t fit the forum requirements. So, i am not stupid. I know the requirements, but i was not able to made it considering the short pc access and internet connectioni have right now.This is why the wiring diagram was not good enough.

I checked the wiring multiple times. It is simple and i do not have any doubt about it.

If you still want to think the arduino is the problem is up to you, but i said that the arduino is not the problem… because the sensors are still not connected to arduino!!! They work out of arduino. And my problem now is about the devices theyself of how i made the circuit or whatever, but not the arduino.

Anyway, you are right… something is wrong… I think i will start again from zero. However, I don`t want to teach, but i think that in your story there is other solution than a husband or a boyfriend, or a miracle… right? :wink: May be this fourth option is what is causingmy problems.

In summary, thanks so much for all your comments. I really appreciate them. Since i can see the light at the end of the tunnel, i will desolder everything and start again.
Thanks!

i will desolder everything and start again.

Hardware is not a Windows system.

All those comparator lm393 sensors "out there" give a digital output (most active-low). The analog output is really just a voltage divider and bypasses the chip all together. Are you using the comparator output as digital, adjustable by the potentiometer, or the A0 pin?

Without getting into smoothing, averages, and blink without delay. analogRead can be noisy. Just add a delay(50); between each reading. You'll see a difference. If the sensors work one-by-one you're reading them too fast and picking up noise from the other.

-Dan

Just add a delay(50); between each reading. You'll see a difference

No you won't that is just rubbish.

there is a protentiometer on the board to set the Threshold value, to outpout logic High or LOW. try to adjust it .

actually, i suggest you using the analog port of all the moisture sensors. in this way, you can get the relative moisture value of all the sensor, such as this:http://www.elecrow.com/soil-moisture-sensor-p-509.html