Hi! I'm new to the forum but love to build projects to help my farm. I'm working on a LoRa relay system to control a remote low voltage latching solenoid for an irrigation system. The solenoid needs a very short pulse to latch on or off (based on polarity). My design is working well, but I'd find it handy to have some simple indicator on the receiving circuit as to which what was the last polarity pulse so I know if the valve is on or off. Any ideas on how to accomplish this? I'd prefer not to use anything that would require constant current.

 

I'd find it handy to have some simple indicator on the receiving circuit as to which what was the last polarity pulse so I know if the valve is on or off.

I'd prefer not to use anything that would require constant current.

The first part is likely doable with a CMOS latch memory (two latches per CMOS chip).

An indicator that draws no power is more difficult.
Perhaps something like this. which has 4 LCD indicators (can be easily expanded) and would run a long time (2-3 years) on three alkaline D batteries.

 

Maybe a mechanical valve position indicator fitted to the valve?

 

What is the value of the "low voltage"?

 

If a zero-power-consumption VISIBLE indicator is what you want, a mechanical flag indicator driven by a solenoid,magnet linkage could work. The solenoid, in parallel with the valve, would push one way or the other to indicate which polarity was last applied. Sort of like a railroad "flag semaphore" arrangement. If an electrical signal were required, magneticly held polar relays have been around for many years. one of those would serve very well.

 

I recall seeing indicators on aircraft that consisted of a magnetic ball inside a window. One side of the ball was painted yellow or green or some other color and the other side of it was painted a different color. I don't know what they're called, nor can I find anything like that today, but the way it worked was a charge was sent to an electro-magnet to flip the ball one way or the other. Once the ball was in an orientation it would stay in that position until a reverse magnetic field flipped the ball into the other position. It took only power to switch it from one state to the other and would use no power to hold an indication. It only used power when switching the indicator. Something like that would be a useful solution to your indicator requirements. Hopefully someone here with greater experience will be able to identify it and help you find what you might be looking for.

 

Found something:

 

Here's another; called a Flip-Dot Display

 

https://pdf.aeroexpo.online/pdf/l3-technologies/ruggedized-status-indicators/176050-15909-_3.html

 

Maybe a mechanical valve position indicator fitted to the valve?

6-9 volt. I plan on 8v.

 

How about a latching relay in parallel with your solenoid?

 

One more consideration is that the control signal is two-wire reversing polarity. So most CMOS would be destroyed unless there was some serious isolation.
I am guessing that the "PICKERING" company has a polarity sensing latching reed relay that would serve to hold the state last sent quite well.

 

6-9 volt. I plan on 8v.

The one I'm thinking of is fully mechanical, doesn't need power, and is moved by the existing valve armature.

 

The one I'm thinking of is fully mechanical, doesn't need power, and is moved by the existing valve armature.

Certainly monitoring the actual valve position will be the most effective method, but it will also require the most invasive installation activities. Given that we have no hint about the actual valve arrangement, it may not be possible, OR, it might be quite simple.

 

The question is, does he need remote monitoring?

 

The question is, does he need remote monitoring?

I think the answer is "He WANTS remote monitoring". Or to be more precise:

I'd find it handy to have some simple indicator on the receiving circuit as to which what was the last polarity pulse so I know if the valve is on or off.

NEED? No. "Find it HANDY"? I get it. He wants to know what state the valve is in when he (probably) applies water pressure to the solenoid.

love to build projects to help my farm.

This doesn't sound like any farm I'm familiar with. But then again, I'm not a farmer, son of a farmer, related to a farmer, know a farmer or anything else related to farming other than those systems where they have a well sunk in the middle of a field with a pump and one of those circular watering rigs. Farms - as I can imagine - would have some major source of power for pumping water. A solenoid valve like what's on my Drip Irrigation garden that is powered by a battery has the type of solenoid valve that uses a pulse to open and a pulse to close. One year I had old batteries in one of those timers. Barely enough power to open the valve but then just not enough power left to shut the water off. I had to go out there and manually shut the water off.

OK, so you want to know the state of the valve at the last pulse. It's not likely there's any kind of lever or manual valve on the solenoid to get a sense of what the position is in. So your idea of a "Last Pulse" circuit that doesn't continuously require power makes sense to me. Those magnetic indicators I posted in posts # 7, 8 & 9 seem attractive to me. IF the solenoid valves are like what I think then this is the only way I can see having a chance to work at all. But there's always the possibility of a pulse failing to be read by the indicator, possibly leading to a false indication. Since you would find it "Handy" then it's not necessary for any real conditions you may encounter. Your last reply:

6-9 volt. I plan on 8v.

seems to indicate battery operated; which makes sense that you don't want a continuous draw of power. It also suggests to me your definition of "Farm" is not the same as I would define. But that's OK. You can call it whatever you want. I just see it as one of those drip irrigation systems that run on a 9V transistor battery. I think, and this is purely my personal opinion, you're going to have more trouble wiring in any kind of indicator, regardless of the consideration for continuous power drain or not. I still have a few battery powered drip irrigation systems somewhere in a drawer along with other drip plumbing equipment. Currently, my wife's gardens are all run from a 24VAC sprinkler control valve. The valve is only open as long as there is power applied to it. Remove power and it's off.

So I leave you with a question: Is this "Farm" nothing more than a garden with a drip irrigation system that is battery powered?

 

I have worked on control systems that included valves with two and three inch ports, driven by air-powered pilot valves. that were controlled by momentary action smaller valves. so it could just as easily be a very large farming operation. OR even vertical farming with LED lighting.
My point being that just because you are not familiar with it does not mean it does not exist.

 

This doesn't sound like any farm I'm familiar with. But then again, I'm not a farmer, son of a farmer, related to a farmer, know a farmer or anything else related to farming other than those systems where they have a well sunk in the middle of a field with a pump and one of those circular watering rigs.

My point being that just because you are not familiar with it does not mean it does not exist.

Never said it doesn't exist. Admittedly I'm not familiar with the likes of what you describe. There's myriads of things I'm not familiar with. Including things I've never heard of. That's why I pointedly asked:

Is this "Farm" nothing more than a garden with a drip irrigation system that is battery powered?

But:

I just see it as one of those drip irrigation systems that run on a 9V transistor battery.

And that doesn't sound like big farming to me. TO ME! Maybe farms DO run on 9V batteries. I always dreamed of an electric car that ran on a single 9V battery and went a thousand miles on just one battery. I was younger then. MUCH younger.

 

Never said it doesn't exist. Admittedly I'm not familiar with the likes of what you describe. There's myriads of things I'm not familiar with. Including things I've never heard of. That's why I pointedly asked:

But:

And that doesn't sound like big farming to me. TO ME! Maybe farms DO run on 9V batteries. I always dreamed of an electric car that ran on a single 9V battery and went a thousand miles on just one battery. I was younger then. MUCH younger.

About 65 years ago I DID make a dragster that ran on a single 9 volt battery. My cousin wanted a car that would beat the others. It was a model about 7 inches long, originally built to be powered by two AA batteries. I changed that setup to use a single 9 volt battery. It did win races but it also had poor battery life. His winnings easily paid for the increased battery consumption, though.

 

Hi guys,
The TS's query topic is:
My design is working well, but I'd find it handy to have some simple indicator on the receiving circuit as to which what was the last polarity pulse so I know if the valve is on or off.

Please keep on topic.

Moderation.