Variable rate using electric motor. Which controller

Operations/Getting Started Getting Started
1

Hi all, from Australia.

I’m looking to implement the variable rate add on to a tyne drill. (Although I just want electric drive, not actually variable rate across a given field as such)
I Have 12 volt electric motors connected via chain drive to the seed and fertilizer shaft on my box.

I’m sure I’ll have many more, but my first question is What would be a suitable motor controller run each motor?
Current draw seems to be less than 10 amps when metering fertilizer.

I assume the motor controller will receive a 0-10v signal from the PCB, and this will be calculated based on some calibration and then corrected based on actual shaft feedback signal (rotary encoder or similar?)

Thanks for any comments

2

SK21s boards are desiged to take the MD13S, wich is rated for 13A. The shaft speed is picked up with a proximity senor. There are different boards in the rate controller folder on SK21s git hub. Calibration is a bit buggy, but other than that it works pretty good. I build a test with 3 motors and fan speed sensor. Each rduino can manage two motor drivers.

In my case i used motor drivers rated for 20a.

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Thanks for the reply and photos, clears things up a little. I also dug a little deeper into the GitHub and found some info that I’d missed first time around.
Looking at your Hall effect sensor for shaft speed, how do you find it for accuracy. At slow ground speeds my fert shaft will only be doing 2-3rpm meaning the pulses might not be frequent enough for Hall effect. I was looking at a rotary encoder with 600 pulses per rev.
My max expected shaft speed is 16rpm so using the above encoder should give me 160hz shaft speed feedback, sound ok?

5

That should work, i used npn sensors. Not sure how the encoder deals with dirt. It might be a bit Overkill though. 160hz means a pulse every 6.25ms. In the app there is a setting for impulses over an under 5ms. You could just use a sproket with more teeth to get the resolution up. And if the sensor fails you don’t have to take the shaft apart. It works good with slow speeds as well. 52ms is no problem for my test setup. There are probably limitations but im not sure what the min. frequncy is.

I want to put a manual together to discribe setup and assembly. But that will have to wait till November and after.

6

On a Cameleon seeding mashine, they made a disc, to mount on the carrying wheel for speed sensing . Wheel is 1,2 m diameter, disc is put at wheel hub, disc is around 40 cm in dameter. Cuts are 3 cm deep, spaced approximate 5 or 7 mm. Sensor pick up from side of disc.
G1031.pdf (135.4 KB)

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Ground speed is looked after through GPS so this is going to be for feedback of shafts to confirm they are doing what they are told.

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Not to use for ground spred, just use idea to get more pulses pr revolutio of your shaft, and show it can last in dirty environment :grinning:

9

Does this look ok for a shaft speed sensor. Looking to aim it at 10b chain so 5/8 pitch.

Any links to something suitable and a bit cheaper would be appreciated. Thanks

10

Just found this amazing item on AliExpress. Check it out! C$1.61 23%OFF | LJ12A3-4-Z/BX LJ12A3-4-Z LJ12A3 Inductive Proximity Switch Three wire NPN normally open

That’s what i used.

Or these will work as well.

Just found this amazing item on AliExpress. Check it out! C$1.42 | Cloweit SN04/SN05/PS-05/PL-05/TL-Q5M/TL-W5/GKB-M0524 5mm Metal Detection Limit Switch 6-36v Inductive Proximity Sensor Switch

NPN - NO normally open