AgOpenGPS - adding rate control - Page 2 - The Combine Forum
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post #11 of 211 (permalink) Old 11-01-2017, 09:37 PM Thread Starter
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Originally Posted by Wedge View Post
Line 57 in get_ppm() you were thinking about disabling interrupts while running that routine but mentioned noise. How much noise were you getting?
I don't think I saw any noise at all, honestly. It's all about averages anyway. I don't think disabling interrupts is necessary, since the get_ppm() calculations are fairly short and quick.
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It looks really similar to any of the other examples for reading flow meters I have seen. You mentioned that it had difficulties with a garden hose supply, but your valve had slop? What valve were you using?
I just used a 3/4" banjo valve fixed in a metal frame. I removed the plastic handle and stuck on a metal handle that I drove with a 2" linear actuator driven by a mosfet h-bridge driver using pwm input from arduino. It actually worked all right. As I mentioned, I couldn't even get a good flow rate with my hand on the valve, and humans are actually very good at PID control. I can't remember what flow rate I was actually shooting for... maybe I was trying for too low a rate that couldn't be done with the pressures my line was under. I recall I did use a nozzle to make sure I had back pressure.

Anyway, some time I'd like to try again!

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post #12 of 211 (permalink) Old 11-01-2017, 10:45 PM
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Why do you think you require 2 arduinos? I've attached the latest AutoSteer module. It does IMU readings, inclinometer readings, full pid, motor driving, communication to and from AOG, Kalman filtering.... I think its uses about 5% of its capacity, the rest of the time it just loops doing nothing.

Would you like me to chop out all the autosteer stuff and leave the basic routine of the timed loop and communication to and from AgOpenGPS?
Fair points Brian! I should have checked the amount that the arduino is currently doing(or not doing!). I guess my current brainblock is finding a reliable way to mesh flow control in without affecting what is there. More play time I guess!

I think I can gut AOG and give it a whirl. Need to get a stable flow version together then find a good way to patch back in to a stable version of AOG.

Hmmm I see rain in the forecast heheheh....

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post #13 of 211 (permalink) Old 11-01-2017, 10:48 PM
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Originally Posted by Beerwiser View Post
Just some thoughts on the physical mounting. Any sprayer I have built with different brands of controllers all want the flow meter some distance away from the flow control valve. Wanting to make life easy and a bit lazy I did mount the flow meter and flow control within 12" of each other on a turf sprayer. The teejet controller could not keep any sort of accuracy. Separate them 24" and all works good. I am just wondering if that could be causing grief when doing anything home made.
I am going to hazard it might be due to valve-induced swirl in the water pattern affecting the flow readings? Probably a good sciency explanation out there.......... all of our meters are about 10' down the way so that shouldn't be an issue!
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post #14 of 211 (permalink) Old 11-01-2017, 11:17 PM
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Have you thought about using PWM nozzles? Feed a constant pressure, use the flowmeter to just confirm volume delivered.

AOG is all metric in the background, so it will be spitting out liters/hectare. Not many countries use non metric so it just makes sense to keep all the calcs in all programs in metric and just display the not metric as a final step.

Last edited by BrianTee; 11-01-2017 at 11:28 PM.
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post #15 of 211 (permalink) Old 11-01-2017, 11:51 PM
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My father is still head sprayer operator and getting him to accept technology upgrades is....challenging. He still insists on the foam markers even though we have the gps guidance and auto shutoff and all that. Frustrating. PWM nozzles are going to be a tough sell with him. If I get something working for this, then maybe have an alternate configuration for PWM?

Good point on the conversions. Less manipulations, less chance for errors.

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This technology is for myself when I run the equipment
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post #16 of 211 (permalink) Old 11-01-2017, 11:51 PM
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Wedge, i think i misunderstood you, when you said you were going to use "another" arduino for rate control did you mean two for rate control or one for rate and one for autosteer? I'm thinking the latter. I'm kinda slow!

AgOpenGPS started out with the goal of turning a relay or two on or off for my air seeder. Never dreamt it would need 3 or 4 USB connections and multiple arduinos. Maybe there is a better way.
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Last edited by BrianTee; 11-02-2017 at 12:20 AM.
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post #17 of 211 (permalink) Old 11-02-2017, 12:24 AM Thread Starter
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Well when you can show him that precise control of the nozzles and sections can literally save chemical and money, maybe he'll go for it. Just like auto steer has become second nature to us, I'm sure he can get used to automatic section control as well. It sure has revolutionized our operation just to have what we have!

Relating to what Brian said about PWM nozzles, even with normal nozzles, spray rates are dictated primarily by pressure. It doesn't matter how many sections or nozzles are turned on, if you maintain a certain pressure, you'll get a certain gal/ac rate at each nozzle. But of course no one calibrates their nozzles, so as they wear, things do get out of spec and most guys never know.

What beerwiser said about separating the flow sensor and the valve makes a lot of sense. I think I had my flow sensor about 1.5 ft from the valve. I tried it on either side of the valve and still had problems! I guess I need a better test stand than my bath tub. Next year when I have a nice heated shop all winter, I might give it another attempt. Having a general, open source rate controller is another piece of the replacing-proprietary-technology puzzle. Be it liquid rates or shaft speed rate (a drill). It goes hand in hand with what AOG does and the next step once you get a functioning rate controller is variable rate. Every section really needs its own rate controller. Even if you do per-nozzle shut off control, I think having a 10 foot group of nozzles controlled overall by a dedicated rate controller is probably sufficient.
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post #18 of 211 (permalink) Old 11-02-2017, 09:44 AM
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Are you all using ball valves for flow regulation? Surely a Ramsey valve would be easier to regulate as it relies upon air pressure and 2 solenoid valves, rather than a mechanical linkage. They are used on most sprayers around here.
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post #19 of 211 (permalink) Old 11-02-2017, 11:01 AM Thread Starter
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Interesting. Never heard of that before. My sprayers use ball valves driven by a gear motors. Most sprayers use that kind of set up as far as I know. Like this: http://www.sprayerdepot.com/Shop-by-...lectric-Valves. There are two kinds of valves, on-off, and regulating. The rate controller runs a regulating valve. And some older sprayers use a three-way regulating valve, which diverts excess flow back to the tank to keep pressure from building too high.

Ramsey valves look very interesting. I wonder why they aren't more widely used in North America?

Last edited by torriem; 11-02-2017 at 11:15 AM.
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post #20 of 211 (permalink) Old 11-02-2017, 11:10 AM
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Originally Posted by BrianTee View Post
Wedge, i think i misunderstood you, when you said you were going to use "another" arduino for rate control did you mean two for rate control or one for rate and one for autosteer? I'm thinking the latter. I'm kinda slow!

AgOpenGPS started out with the goal of turning a relay or two on or off for my air seeder. Never dreamt it would need 3 or 4 USB connections and multiple arduinos. Maybe there is a better way.
One for rate and one for the autosteer(and everything else that it is currently doing)!

Then it just becomes necessary to grab speeed and width information, either from the autosteer arduino or directly from AOG. If I move pins around I should be able to find enough space to run a comm line between arduinos.

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