# Someone shoot holes in my wireless pump control idea



## splatz (May 23, 2015)

I have a site that's similar. Stormwater overflow goes into two underground tanks; the tanks are pumped into a pond; the pond is pumped into two spray irrigation systems in two areas. 

We use simple pump controllers with floats in the tank plus an interlock from the pond level. We use a 4-20ma transducer in the pond with a fancy pump controller that runs both spray irrigation systems. 

No PID, no VFD so I am just guessing about extending the analog signal with a wireless link. I am going to bet it's fast enough. After all pond level doesn't change super fast unless your pond is tiny and your pumps are monsters. 

The limiting factor isn't the speed of the radio signal (it's at the speed of light, faster than the electrical impulse) it's the lag introduced by the conversion at either end. But that's not really much lag for something like this. You have some processing lag with any PLC where there's remote IO, especially over ethernet, which may be fast but is not deterministic. 

The challenge for me would be interlocking the big pump reliably with a wireless link, but that's doable. And putting in some SCADA that monitors and logs the whole thing, which could include that interlock. 

The transducer, by the way, was a pain in the ass, least reliable thing in the system, it was from KPSI. Has to be cleaned periodically, yuck. A surge came into the system once over the 4-20ma line and messed the pump controller analog card. I installed a surge protector between the transducer and the controller in the panel and the next time the transducer got wrecked the surge protector got whacked but nothing else. 

I am guessing the reason they monkey with the speed is to guesstimate when they'll drive by later and how much to pump down by then. In other words the PID loop is in their head. With automation, there's no need for a PID loop, the pumps are on standby at all times.


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## JRaef (Mar 23, 2009)

I think your approach sounds good. You can probably experiment with accel / decel rates to create a crude PI control system when you have such a slow response to change like that, but implementing the Sleep function will be a challenge, so I would probably do it with the VFD's PID control just to get that. Forget the D though, you don't need it.


I would probably go with a hard wired analog signal though, or maybe a comm link to get the pond level back to the VFD; 1200' is not that far. Radio and analog can be tricky, i.e. someone keys up a walkie-talkie nearby and you get a spike in the analog value. I've seen that happen, despite all of the radio transmitter people swearing that it would not.


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## MikeFL (Apr 16, 2016)

underground (or aerial) conductors on a farm can be tricky as well.


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## Cow (Jan 16, 2008)

I'd love to run conduit and hardwire it, as 1200' isn't anything we haven't done. Problem is, there is a county road and creek between the pond and pump location that makes that impractical.

Good to know about keying up a walkie talkie potentially causing problems, I will keep that in mind.

I appreciate the feedback from everyone. Thank you!


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## sparkiez (Aug 1, 2015)

Have you heard of our lord and savior, ubiquity network radios? I have not personally used them, but have heard some great things about them. It may be much, much easier to do a setup such as:

Solar at pond for power. You won't need much. Have a radio there, and the little bit of instrumentation you need. This will also be much cheaper than the PC solution. Or, since it looks like you may already have power near the pond, I would do something similar to this:

Fill pond based on level. Use ubiquity line of sight to send signal back to well pumps to start/stop. Use some sort of PLC as intermediary. I'm fond of the P1000 series. You could also integrate your VFD monitoring via data-link into this setup, and with a proper gateway let the guys monitor it from their cell phone.


Then, you can just run conduit to the booster pumps and hard-wire data and/or control wiring if it isn't already in place. For only 75 feet, I would much, much prefer to have a hardwired setup.


Then, it wouldn't take much to do mobile alerts if something went wrong so that they could check it out.


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## JRaef (Mar 23, 2009)

Check this out. Using SMS messaging for the wireless control, so it's not continuous and subject to interference.








Here is the Cellular modem they showed (but not mentioned) in that video.
https://www.inhandnetworks.com/products/industrial-gateway.html


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## splatz (May 23, 2015)

The Ubiquiti products are a very cheap wireless communications but wifi is not the best protocol for something like a PID loop which you want to be as close to real time as possible. SMS would be even worse, way worse. 

There are lots of wireless modems that make a point to point link, you can pick a frequency that's got no other traffic easy enough to avoid interference from walkie talkies, cell phones, wifi, etc. 

Could you just use the discharge side pressure for the well pump control so the well pump doesn't really need to know the pond level irrigation running etc.? I'd just want that interlock going back so that if the pond's full the well pump is interlocked.


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## ElectricMatt (Dec 29, 2016)

I have used an Elpro radio with yagi antenna for a similar application controlling pumps from a lake based on the level of a water tower. Our distance was around 10 miles as the crow flys. 

The antenna at the tower is has about a dozen other antennas mounted to it, and I had no issue with interference. We used a horizontal polarization of both antennas to help cancel out transmission from the other antennas and other small radios. I placed a micro 820 and just used discrete input and outputs over the radio frequency to reduce any conversion lag. 

The communication from site to site is less than a second. I ran several tests in different conditions and never had any issue. The yagi antenna is key in point to point communication over radio. 

http://www.cooperindustries.com/con...ton-datasheets/wir-td-032084-en-905u-1234.pdf


Sent from my iPhone using Tapatalk


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## sparkiez (Aug 1, 2015)

splatz said:


> The Ubiquiti products are a very cheap wireless communications but wifi is not the best protocol for something like a PID loop which you want to be as close to real time as possible. SMS would be even worse, way worse.
> 
> There are lots of wireless modems that make a point to point link, you can pick a frequency that's got no other traffic easy enough to avoid interference from walkie talkies, cell phones, wifi, etc.
> 
> Could you just use the discharge side pressure for the well pump control so the well pump doesn't really need to know the pond level irrigation running etc.? I'd just want that interlock going back so that if the pond's full the well pump is interlocked.



I guess I should specify here that a PID loop is absolutely not needed, nor is it the best solution, or even close to the best solution to controlling the fill rate of that pond. Discrete levels are the best way to keep that pond full. The most you may have to do is pay some extra attention to the rate liquid is leaving the pond in order to verify you start filling soon enough, but that isn't really a problem for a PID either.


Provided that the well heads can provide water at a rate faster than the irrigation equipment can spray water, it will never be an issue, and it sounds to me like that is the current setup.


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## Helmut (May 7, 2014)

Cow said:


> Well pump is 1200' from the pond it fills. Booster pumps are 75' from the pond they are drawing from. They start and stop everything by driving around and pushing start. They control the amount of water filling the pond by eyeballing it and adjusting speed manually on the well pump VFD based on how much they are drawing out of the pond each day. The pond is susceptible to overflows or going dry and starving the booster pumps. Loss of prime functions being added to the booster vfd's is also on the list.


How big and deep is the pond?

Does the main line, and booster pipe lines have gallon meters on them?

Wireless sounds like a neat idea any idea the cost for 2 stations?


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## just the cowboy (Sep 4, 2013)

Keep it simple. 
Pond level into CLick PLC with analog and enet @$150. 
Engenius ENS500-AC access point/bridge. @$99 at pond.
To a enginus 500 access/bridge at drive. @$99
To CLick PLC with analog and enet to VFD reading level from pond @$150 .
Program it like you said with a level to output step control keeping it simple.
You can add a Cmore micro HMI for not much more to change setpoints.

All software is free.

Cowboy


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## Cow (Jan 16, 2008)

splatz said:


> The Ubiquiti products are a very cheap wireless communications but wifi is not the best protocol for something like a PID loop which you want to be as close to real time as possible. SMS would be even worse, way worse.
> 
> There are lots of wireless modems that make a point to point link, you can pick a frequency that's got no other traffic easy enough to avoid interference from walkie talkies, cell phones, wifi, etc.
> 
> Could you just use the discharge side pressure for the well pump control so the well pump doesn't really need to know the pond level irrigation running etc.? I'd just want that interlock going back so that if the pond's full the well pump is interlocked.


The well pump discharge line is a standpipe that discharges above the pond water level. I'm not sure that even if they cut the pipe off below the water line, that I could sense enough of a pressure differential to regulate the pond level accurately. I did think about it though, but it'd be rough to go to the trouble of cutting it off and be wrong.



ElectricMatt said:


> I have used an Elpro radio with yagi antenna for a similar application controlling pumps from a lake based on the level of a water tower. Our distance was around 10 miles as the crow flys.
> 
> The antenna at the tower is has about a dozen other antennas mounted to it, and I had no issue with interference. We used a horizontal polarization of both antennas to help cancel out transmission from the other antennas and other small radios. I placed a micro 820 and just used discrete input and outputs over the radio frequency to reduce any conversion lag.
> 
> ...


Good info, thanks.



Helmut said:


> How big and deep is the pond?
> Does the main line, and booster pipe lines have gallon meters on them?
> 
> Wireless sounds like a neat idea any idea the cost for 2 stations?


Looks to be about 8 feet deep and 50-60 feet across.

No flowmeters.

I estimated around $5k all in, the customer stated he will stick with driving around and pushing start buttons.

I figure I'll keep picking up info along the way about what may work best or better than what they have now as far as automation goes. At some point I'll have them talked into something less manual. I just have to chisel away a little every time it comes up.....:biggrin:


just the cowboy said:


> Keep it simple.
> Pond level into CLick PLC with analog and enet @$150.
> Engenius ENS500-AC access point/bridge. @$99 at pond.
> To a enginus 500 access/bridge at drive. @$99
> ...


You know, I've used clicks before, and looked into this option coupled with some nanostations. 

However, I dismissed it because I thought with the time and money to build the control panel and programming that it'd end up a wash versus the phoenix contact radio's that just need a thumbwheel turned to sync them together for a master slave setup. No programming or control panel to build.

I may end up purchasing some clicks or do-more's at some point and a set of wireless bridges, just to teach myself. I have four do-mores on ethernet with an HMI running a feed mill since Oct of 2015 that hasn't given me any issues. I've just never done wireless. 

Thanks again for the responses.


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## Helmut (May 7, 2014)

Cow said:


> Looks to be about 8 feet deep and 50-60 feet across.
> 
> No flowmeters.
> 
> I estimated around $5k all in, the customer stated he will stick with driving around and pushing start buttons.


Kinda what I thought. It sounds as if the pond isn't big enough.
Might be cheaper for them to dredge it deeper, and install flow meters on lines.


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## splatz (May 23, 2015)

Cow said:


> The well pump discharge line is a standpipe that discharges above the pond water level. I'm not sure that even if they cut the pipe off below the water line, that I could sense enough of a pressure differential to regulate the pond level accurately. I did think about it though, but it'd be rough to go to the trouble of cutting it off and be wrong.


OK but why the analog control? 

Two floats (high and high alarm) and an e-stop, maybe a HOA at the pond - both interlock the pump when floating, high to stop the pump, high alarm interlocks the pump and sounds an alarm, HOA can defeat the high float but not the high alarm float. Arrange the controls to fail safe in case of loss of signal, etc. If it's really critical it's very easy to make the floats redundant, I have had floats fail, but hasn't happened since switching to a better brand. 

You can get all kinds of wireless contact closure devices that will transmit the interlock back to the well pump for cheap, in the $100 to $400 range. You could get one with 4 channels for a few extra bucks so you have room to expand if you need to. 

You can definitely do this with ethernet and ethernet capable PLCs at both ends, but do you need to? The old saying, when you know how to use a hammer, everything looks like a nail? I think now that PLCs and wireless ethernet are cheap, people forget there's other costs involved, writing the program, testing the program, keeping backups, etc. etc. 

If the customer is really "cost sensitive," I'd start with floats to pump down the pond automatically and alert if the pond gets too high. Low float, low-alarm float, high float, high-alarm float, a pump controller, an HOA switch, al alarm light / buzzer, an enclosure, and you're done. When they see there's some value in the time savings and reliability, phase two will be beaming the interlocks bad to the well pump.


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## Cow (Jan 16, 2008)

splatz said:


> OK but why the analog control?
> 
> Two floats (high and high alarm) and an e-stop, maybe a HOA at the pond - both interlock the pump when floating, high to stop the pump, high alarm interlocks the pump and sounds an alarm, HOA can defeat the high float but not the high alarm float. Arrange the controls to fail safe in case of loss of signal, etc. If it's really critical it's very easy to make the floats redundant, I have had floats fail, but hasn't happened since switching to a better brand.
> 
> ...


The reasons I chose analog, over something with a discrete signal like floats or probes, is debris and vegetation in the pond. I knew floats would eventually get tangled up in the tall marsh grass that lines the pond, and the probes would have a similar fate.

It seemed easier to drop a submersible level transmitter into the pond, and hold it off a the bottom a little and go with it.

The other main reason is I know a PI loop would attempt to maintain a constant level and keep the pump running unless it hit the min pump speed and was still overtaking the amount being drawn out, then it would go to sleep. I like the idea of the pump staying running, more than I like discrete setpoints from a low-high or similar float setup that would cycle a deep well turbine pump on and off. 

I have no problem doing floats with say, a sump pump, but not a mission critical 200hp well pump with no backup and crops on the line.

The higher initial cost of the system I proposed seemed like a worthwhile tradeoff in my opinion over the long run.

Like I mentioned earlier, I may have been able to do low, medium, high settings with discrete, but I don't know of a device other than floats or probes that would work reliably in the pond they have.


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## gpop (May 14, 2018)

phoenix contact radio's are easy to install. The ones we use do need to be programmed via a laptop but that's easy to do even with no prior experience. 

To be honest you are just making a point to point wireless bridge so there are cheaper versions that will work just as well as you have no trees to worry about. 

A anolog pressure sensor is cheap and easy if you can find a good place to mount it. (it should be hung so it doesn't touch the bottom of the pond)

The best place would be inside a 6" pvc tube that is 8" from the bottom of the pond. (floats would work just as well using the same type of set-up with a 12" pipe). The down side is you will either need a dock to get to where the you can reach the deep part of the pond or you need to have the farmer to dig you a channel. 

I would probably go with floats to allow the farmer the ability to reset the levels with out having to get to complicated. Use radio's that have simple digital inputs on the float side and digital outputs on the control cabinet side then add a few timer relays and keep every thing hardwired. The only reason i would go this way is to keep the diagnosis as simple as possible for the farmer.

This float turn on this input light on the radio. Go to the other side and you will see the output light on the master radio should now be on.


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