Overwater timer for center pivot irrigation

inwo

Joined Nov 7, 2013
2,419
The first one shot timer assures time out if stopped in any position.

Switch or interval timer failure still times out.

The same circuit works with an encoder. A standard encoder is just a switch with many pulses per revolution.

The one I linked to is 200P/R at 1-1 gear ratio to pipe.

Depending on the specs an encoder may not need the one-shot/interval timer. It may not "hangup" in an on or off position.

In that case, just connect output of encoder to "reset" of a delay timer relay.

edit
I would keep the pulse count low. It's easier to tune and trouble shoot if you are watching a timer set to 5 seconds or more. In your case 5 minutes minimum.

I believe you know this as per mention in first post.;)
 

inwo

Joined Nov 7, 2013
2,419
96H X 60 = 5760M

5760/5M =1152 pulses per rev

24H X 60 = 1440 or 288 pulses per rev.

So shoot for 200 - 1000 pulses per rev. IMO

I like 200 - ~7 minutes on the fast one ~28M on the slow.
 

Bernard

Joined Aug 7, 2008
5,784
I was thinking of a 5 mm pitch rather than 1/5 in because I have a strip which gives about 129 pulses / rev. @ 96 h time delay about 1 h. Not too hard to use a small gear, around 2 in dia to give a 4 to 1 boost X nunber of holes in small wheel, say 5; 129 X 4 X 5 = 2580 pulses/ rev. or 2.2 min/pulse = alarm after 5 min?
If one wrap does not come out even, then a thin shim strip can be added first, of a thickness about 1/6 of the overlap, also counting glue[ epoxy] thickness.
What electrical power is available??
There is no problem with high centering counter wheel as cog will generate a short pulse to reset 555 timing cap.
A coarser timing belt might be more reliable with its taller cogs.
 

inwo

Joined Nov 7, 2013
2,419
Last edited:

Thread Starter

djreiswig

Joined Aug 8, 2008
120
Any encoders like that available from a US seller? I don't buy things that ship from Hong Kong. I don't know the specs on them, so I don't know what to look for.
 

inwo

Joined Nov 7, 2013
2,419
Here is a 600 P/R one.

I don't know your mechanics. I'm guessing an increase 4X coupling.

That would be 2400 pulses in 24-96 hours.

A pulse every 2.4 minutes to .6 minutes.

That seem too fast for your suggestion.
Can you do a 1-1 coupling?

I don't want to pick for you.:cool:

Look for a voltage your comfy with. 24vdc seems good.
The P/R for the timing you want. 5min-1hr- 100-200 P/R seems good.
And an open collector output.

I hope someone double checks my math.:p I'm not spending a lot of time on this.

Edit
midnight
I worry too small a step will give false alarms from jitter.
 
Last edited:

MikeML

Joined Oct 2, 2009
5,444
If you believe the claims made by the manufacturer, why is this even necessary???

T-L’s hydrostatic drive delivers numerous advantages electrically driven center pivots can’t: Continuous machine movement, which is critical to uniform water distribution, especially in low-pressure situations; Improved traction reducing the chances for getting stuck; and a constant-pressure-variable volume hydraulic pump ensuring full torque at any speed.

Our center pivot’s unique alignment control valve will stop the system if the system gets stuck or seriously misaligned. A sensor will shut off the water at the same time. Structural and crop damage are avoided. T-L drive units, unmatched in strength and traction, receive continuous power to each wheel from hydraulic motors that are directly coupled to the final drive gear assembly.
 

Thread Starter

djreiswig

Joined Aug 8, 2008
120
Yeah, that would be all set up on a new one. This one is about 30 years old (and still running), but it doesn't have all of the cool gadgets on it. The OEM sensor to shut the water off is about $500.

inwo,
I appreciate all of your help. For that matter, I appreciate everybody that has posted to this thread.

I'm not sure about the encoder. I don't know much about them. I was thinking a wheel on the encoder shaft with a large o-ring running against the 8" pipe should work. I could make the wheel any size, but 3" or 4" seems reasonable. I'm not sure what that does with your ratios.

As far as the voltage. The sensors on the unit are all 12vdc as it is run by a diesel engine. Are there any encoders that will work with 12vdc?

I agree that the short pulses might cause a missed shutdown if there is vibration. Probably should shoot for less pulses. An acceptable shutdown would be under an hour. Probably closer to 1/2 hour if possible.
 

inwo

Joined Nov 7, 2013
2,419
All the encoders I've seen will work on 12vdc.

Using your 1/2 hr guide line. 96 hrs = 192 1/2hrs. That would be 192 P/R

Your gearing is in the X3 range so 192/3 = 64 P/R

Or only 16P/R for the 24 hour model.


I'll keep looking as time permits.

This would all be moot if you used a "smart" controller. Then you could count pulses.

I still like to keep it simple, but then, the P/R will control the alarm time.
 
Last edited:

Thread Starter

djreiswig

Joined Aug 8, 2008
120
"Smart Controller"? What are we talking about cost for doing it that way? Sounds complicated, but if it is more reliable, and easier to set up. As long as it isn't really expensive, that could be an option. But since I don't know anything about them, that would take even more help on your part.

Thanks.
 

inwo

Joined Nov 7, 2013
2,419
Here is a supplier of encoders down to 100 P/M

http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Optical_Rotary_Encoders/Light_Duty_Incremental_Encoders_%28Quadrature%29

Could be I've been thinking of this the wrong way.:p

Should be no reason that the alarm timer couldn't be set to 1/2 hour even receiving pulses every 10 seconds.

It would just reset more often. Yet still alarm with no pulses in 1/2 hour. duh!

Too sensitive would still jitter.
I'd go with the 100 P/R

Now the next thing. Find 12vdc timers!

edit:
The Omron link shows (24-48AC/12-48DC) models

Should be good to go!
 
Last edited:

Thread Starter

djreiswig

Joined Aug 8, 2008
120
So, with your knowledge, pick the 2 you think I should order. You know about as much about my application as I do, and more about the electronics.

How do I go about wiring this up. Just connect the pulse wire from the encoder to the reset terminal on the timer? I have used timers before, and have seen encoders, just never paired together.

Thanks for all of your help.
 

inwo

Joined Nov 7, 2013
2,419
"Smart Controller"? What are we talking about cost for doing it that way? Sounds complicated, but if it is more reliable, and easier to set up. As long as it isn't really expensive, that could be an option. But since I don't know anything about them, that would take even more help on your part.

Thanks.
If only "Strantor" was available, he uses smart relays all the time? I use small plcs.

I'm not ready to change horses now. You can research if you like.
 

Attachments

Thread Starter

djreiswig

Joined Aug 8, 2008
120
I skimmed the manual. Looks intriguing, but looks like about $200. I think your way will be less expensive, and work just as well.
 

inwo

Joined Nov 7, 2013
2,419
So, with your knowledge, pick the 2 you think I should order. You know about as much about my application as I do, and more about the electronics.

How do I go about wiring this up. Just connect the pulse wire from the encoder to the reset terminal Pretty much. on the timer? I have used timers before, and have seen encoders, just never paired together.

Thanks for all of your help.
I'm not going to go so far as to pick the exact models. Not because I don't want to be helpful.:D

I'm prone to mistakes.:( Most of my projects go to the 2nd or third try.

Just so we're on the same page.
I'm suggesting a two timer solution.
The first outputs a single reset pulse for each step of the encoder.

From my Omron universal timer link. Pick:
12vdc power
no-voltage input
contact output
11 pin

The second timer sets the alarm time.
My diagram uses an 8 pin delay on timer 12vdc

A second universal 11pin timer could also work if you want to use the same timer in both positions.

I would just have to redo schematic.

I would be happy to critique your selections.
By posting them, others might catch our mistakes! :D
 

inwo

Joined Nov 7, 2013
2,419
I just tested a 11 pin timer for use as the second timer.

It works fine, replacing the 8pin simple timer, by just jumping the start pin and cycling power to reset.

So two of the 11 pin timers will be fine.
 
Top