Hardware needed for sprinkler plus water pressure monitor

Official Hardware MKR Family MKR GSM 1400
1

Hi all. This is my first post from Spain and haven't even received my hardware yet, so please, be understanding on my mistakes.

I am looking to build an sprinkler control plus pressure monitor for my family farm field irrigation system.

I chose the Arduino MKR GSM 1400 because I need the wide range of voltaje input due to the solar powered nature of the available electricity, and also a GSM interface to control the board though SMS commands and let it report with some more SMS sent to my phone.

For the board I found the box named ArduiBox MKR Standard with transparent lid very convenient since it provides further aid with incoming voltage and a nice package to put my devices before attaching it to the DIN rails.

Also I expected to use a relay to open and close a 12 volt LATCH valve, and this one named Grove - Relay feels ok.

But here start the doubts. That relay uses a connector that seems to be expecting the shield Arduino MKR connector carrier - Grove compatible. Isn't there a better way? I do not think that will fit into the nice looking box, would it?

And finally the mother of doubts. Isn't there a water pressure sensor I could use? I need it to use a 1/4" slot to attach the sensor into the pipes, but that is likely secondary since an adapter could always be used.

Any help would be very much appreciated. I have seen and already read the sprinkler thread (not fully read, it is quite long). Also read some info about opensprinkler, but that one uses 24VAC and that simply does not fit my scenario with my 12 VDC power sources.

Thanks a lot for your aid and the time you took to read this far.

Regards,
Jose

2

What is your scenario? How long are the 12 volt wires going to be? There is a good reason for the 24 VAC or they would not be using it! Do you understand about wire resistance and voltage drop?
What material are your "pipes" made of? Metal or plastic?
Spend some effort on describing your power supply system for the sprinkler system.

3

Hi, @Paul_KD7HB.

Thanks for the time reading my questions.

Yes, I do understand how voltage and resistance works. My valve is about 2 meters away, so I shouldn't loose much voltage even using a thin wire.

24VAC would be much better and would let me place more valves around the farm without too much trouble and no electricity changes. Probably with just one more relay to be closed when needed and that would be it.

The thing is that there is no electricity at the farm. All we have comes from a small solar panel with a 25w driver combined with a 70Ah car lead-acid battery that provides those 12 VDC I was talking about. More likely something between 12 and 16 volts depending and how charged the battery is. But with the board/case I mentioned it should work just fine since it reads 8-35 volts input (I hope I read it right).

We could purchase an inverter/oscillator to "make" the 24VAC supply but it would defeat the purpose of simplicity and trial run we want. Also, I could not find any at a reasonable price point while capable of working under the hard sun of Spain for a long time and some reliability, so I would rather focus on solving the current problem with the valve at 2 meters than to think about the maybes of the future expansion or accommodate the OpenSprinkler that also lacks GSM support. If in the future I need another valve too far away for DC current to work reliably, I will just add the inverter and another relay for that valve. Also, 24VAC are active valves, meaning the must use power to keep the valve opened or closed, so in my low power design I rather use a 12VDC latch valve that does not require 24hours powered controllers. The current valve could still work on DC even then keeping the inverter as unused as possible for longevity.

The pipes are made of polypropylene and the plug-in where the pressure sensor is connected to is made of polyethylene. Both able to withstand pressures above 6 MPascals. The "hole" for the pressure sensor is screwed female with a quarter of an inch in diameter. I currently have attached an analog manometer, but that cannot be read from any device that I know of to the meassurement report it over the internet or the GSM network.

I probably forgot to tell that irrigation water comes from a valley wide distribution system we joined recently, providing us unfiltered water though some 4" wide pipes (metal made) that end up 2 meters away from the solar installation (that is not coincidental).

I hope I explained all you were expecting. Please, ask me again if not. English is not my mother tongue but I shall do my best.

4

really?? more than 800psi..
was going to recommend..
Gravity: Analog Water Pressure Sensor
but it will not do that pressure..

Normal Operating Pressure: ≤2.0 Mpa

good luck.. ~q

5

I hope they are NOT light transparent because algae will grow, otherwise.

Your English writing fooled me. Must have been around Americans a long time!

One thing on pressure sensors. Are you aware that any type pressure sensor can be mounted vertically above the water pipe/tube so it has an air column to keep water away from the sensor mechanism, will work for you. I have had a regular air pressure gauge that way on my irrigation system for 15 years and still works perfectly.

Is all your water pressure coming from the 4 inch delivery pipe? Do you have an agreement that the water pressure will be a fairly constant value?

For unfiltered water, I would recommend at least a screen with small opening to protect your system. Your system won't work well is the valve is plugged or sprinklers are plugged.

What is your altitude? We are at 2800 ft and experience frost on the ground when there is NO wind and the air temperature drops to 42F. The evaporation from irrigated ground cools the air to freezing.

6

@qubits-us, thanks for reading. And apologies for my mistake. I was trying to provide understandable pressure units since I could not convert into PSI from the top of my head and I messed up. I meant 6 bar, usually around 4 bar. I have been told the water hammer here is pretty rough since other people on the same pipe close their valve without care and the overpressure generated peaks pretty high. I guess I should use a pressure limiter valve before the sensor so I do not need a monster unable to measure the normal changes in pressure. So 4 bar, maybe 6 bar at full scale should suffice. Awesome website to look for sensors, OI just hope they can work with Spain in Europe too. Thanks!!!

@Paul_KD7HB, thanks for your interest. The pipes are carbon black made so they can withstand the UV radiation under the sun. They in exchange expand and shorten quite a bit because of the heat they absorb and radiate, but surely last a lot longer than any other.

I am not sure about the dry measurement though. Did you have a chance to compare the proportions of the air pressure compared to the actual water pressure? I do have a unused filter on the pipe that uses a vertical column usually filled with air since there is no way out for the air trapped inside. I could work on the tip may be to attach a air pressure sensor there if it was air-tight (we do not want the water rising up to reach it I guess).

Unfortunately there is no guarantee in the contract. They assume that water will just flow out of the pipe. Sometimes the pressure is as low as half a bar. Others it rises to 4 bar without notice. And they advice to protect any sensible system agains water hammer effect. In the end, they provide with 10 litters of water every second, and that is it.

Also, yes, I was planning on adding an small filter before the pressure sensor to prevent damage. It complicates things a lot with adapters, closing valves for cleaning, and a few smaller pipe segments, so I wanted to give it a first run without, but you are probably right it is not worth damaging the sensor and then doubting the measures taken. From the valve down to the irrigation system there are like 50 filters already, so the droppers do not become obstructed. Also the latch valve requires a couple of them too since the control section cannot be obstructed either. Too many filters though. It becomes really messy to deal with them all.

On winter there are some month when the ground frosts on the surface, but it is very superficial and by then the irrigation system is empty. We can only use it from spring to autum. We are at around the same altitude above sea level and similar temperatures in spring and autum, sometimes no wind because it is placed on a not so wide valley, but so far we felt there was no freezing to worry about other than the superficial frost on the ground and pipes. Why does it bother you? I am not sure I understood the issue you are providing advice for? Could it be because of the sensors I was planning to set up? I cannot place the pressure sensor in a case like I can with the power source and Arduino, but I was expecting those sensors to be IP65 rated or more. Please, explain if you can spare the time.

Thanks a lot to both of you. Any word you could come up with regarding the sensor connector shield and the selected casing?

Thanks!

7

Well, I had a feeling it was off, no worries..
Sensor should work and yes, it works in spain too.. :slight_smile:
This all reminds me of when I had a well for water at home..
Curious, would a well pressure tank help with the non constant pressure and hammer affect??
In florida, no freeze either, was born up north..
pipes tend burst when they freeze with water in them..

good luck.. ~q

8

Since a liquid is NOT compressible, it has NO pressure, but TRANSMITS the pressure of it's source throughout the entire volume of liquid. That source pressure DOES compress the air that contacts the water.
Water hammer is caused by steel pipes or other metal that cannot expand when the pressure front hits the pipe. Since you have plastic that is very flexible and will easily expand when the pressure wave hits it, you will have no problems. Old homes plumbed with steel pipes had to have air pressure tanks to absorb the pressure wave and stop the "hammering" or movement of the pipes. Modern homes all use plastic tubing and know nothing of water hammering. Same with frozen pipes in the winter. Plastic tubing will expand and contract. They also will not allow ice to form on the inside surface of the tubing, like steel pipes do.

Sounds to me like you are all set to go with a usable system.

Good luck!

9

@josiin “ I am not sure about the dry measurement though. Did you have a chance to compare the proportions of the air pressure compared to the actual water pressure?”

The pressure of the air will be the same as the water pressure. No conversions necessary.

The affects of water hammer can be mitigated by using a gauge damper. I did a quick google search and found lots of references. I used the phrase “pressure gauge damper”

As far as water having no pressure I worked in the industrial instrumentation field and measured water pressure on thousands of systems. I guess if you want to get esoteric about it you can worry about whether the water has pressure, but i guarantee that your sensor will not be concerned in the least about the question.

10

You measured the pressure of the pump or whatever was moving the water. Remove the pump and no pressure.

12

Like I said, if you want to get esoteric about it. You don’t even need a pump. If on the other hand you want to live in the real world, a pump only creates flow, the resistance to that flow creates pressure. (Dynamic head) Also if that pipe runs downhill there will be static head even with no flow. Please don’t tell a dam operator that there is no pressure. Or the crew that has to plug a leak on the penstock.

Anyway, this discussion will not get us anywhere closer to the pressure monitor that we are trying to create. So if you choose to reply then you have the last word.

13

That implies that as long as I can keep the air column air-tight, I can use an air pressure sensor that cannot get wet to meassure the lets say water pressure. I will look into those too.

I also had a deeper look at the sensor provider for the water sensor and it does not look simple to purchase from there here in Europe. Import taxes are not dealt with and purchasing can become a nightmare in those cases. I will look for another vendor that already takes care of the import stuff for me.

All issues but one have been addressed. Can you please advice on the compatibility of the connector board with the casing of choice? Do any of you guys have any first hand experience with the casing or the connector board? Any piece of advice? They still seem incompatible to me, so perhaps I should purchase the casing only and solder in the connectors to the included board. What do you think?

Thanks a lot!

14

Be aware that the air in the system is going to be very humid and possibly saturated with water. Any sensor you use will have to tolerate those conditions. Also the air in the vertical tap will eventually dissolve into the water. You should use a sensor that is compatible with water. The price cannot be all that different.

15

True. I will look for both just in case, but the installation of the water pressure sensor would be pretty straightforward since the filter case already provides the 1/4" connector.

Still nothing on the connector shield vs the ArduiBox? Pretty please with cherries on top...

16

Digging deeper into the professional area I found this Arduino Edge Control — Arduino Official Store. Looks awesome and expensive. Would you recommend it?

17

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.