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Forum Index : EV's : RC lawnmower

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nickskethisniks
Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 159
Posted: 02:08pm 18 Apr 2020
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Hi,

One of my new projects:
https://www.youtube.com/watch?v=CzqItc3o52s

It's still under construction. I will open a topic in the electronics folder soon.

I still need to work on the mowing deck but I'm waiting for parts. The deck will also fit under my sit lawnmower that's also converted to electric more on that later.

The thing is controlled by a 2,4ghz 6 channel transmitter, I hope to use a channel to control the blades from distance. I build 2 bldc controllers for motors with hall sensors. I designed it myself and wrote a program in arduino to decode the receiver signals.

Currently it's powered by a 20ah Lto battery, but I think it will need a better battery, It got warm (maybe 30°C) during a test so I don't know, I first need to finisch the bms for it.

I'm not finished with the construction of a 14 cel li-ion 100ah battery, it's exactly half finished, it's the same as the sit lawnmower.

That's for now, soon some pictures from what's under the hood.
Edited 2020-04-19 00:39 by nickskethisniks
 
Ralph2k6

Senior Member

Joined: 24/09/2017
Location: Australia
Posts: 129
Posted: 10:42am 21 Apr 2020
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Impressive start  
Ralph
 
Davo99
Guru

Joined: 03/06/2019
Location: Australia
Posts: 473
Posted: 12:01pm 21 Apr 2020
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Very impressive.  I have seen RC mowers on Yt that use a petrol engine and are used on  steep inclines because of their Low COG.
Is that going to be the platform size or will you expand the base more? Be interested to see what you use for  cutter motors.

As much fun as the RC may be, I'll stick to my Diesel Ride on.
I have too much fun on that reliving my younger days pretending I'm driving a go kart.

I just made a 3 Point hitch for it and Now I'm going to build a loader bucket for the front to make it a mini tractor.

Now all I need is about 5 ton of sand and I'll be able to live out all my unfulfilled childhood dreams as will you with the ultimate big kids remote car.

" But Honey, I'm not playing with my RC toy, I'm mowing the lawn for you...." :0)
 
nickskethisniks
Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 159
Posted: 02:12pm 02 May 2020
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I will use a goldenmotor 5KW 48V, I just did a test ride on 24V and it was actually just enough to cut the long grass with sharp blades. No load was 20A, I think around 60-70A when cutting the high grass. It is used in combination with a Kelly kls6035.

I replaced the old mosfets in the diy motordrive with Hy4008, they were hot after 20min but I was not ecoriding. So I need active cooling in the future, or use parallel mosfets. There is something wrong with the left hubmotor, there something loose in it. So I need to fix that, could be there is one hall sensor loose…

It was not the plan to use the goldenmotor, I wanted to use 2 stiga 48V 1500W (don’t know about that is you look at the size of them compared to the goldenmotor). The goldenmotor was for the traction in the sit mower. But I need to wait for parts (hub to mount the blades on) for another 2 months....

I will soon post another video.


Here is a picture of the mowingdeck under construction.








Edited 2020-05-04 17:42 by nickskethisniks
 
nickskethisniks
Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 159
Posted: 07:15pm 06 May 2020
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Disaster struck, I was talking about a strange noise in the left wheel previous post, so I discovered there were magnets loose…. 5 of them… And after opening the wheel it was an easy job to loosen all the other magnets….  It’s a mystery how that can, what I did notice was that I didn’t positioned the hall sensors optimal last time.

The controller is acting badly as well, timing is bad, and I think that’s why my controller ran hot after 20min. Thinking about that it’s a wonder I didn’t blow mosfets… I think the current limit is working well. The wheel was not spinning properly, and no load current would be extremely high I guess.

So since it will not be a joy to put the magnets back in I spent a whole afternoon putting hall sensors in another wheel. I have 5 hubmotor wheels like this… But they don’t have the hall sensors in yet, there are, but only 2, I use 3. It’s possible they are cos sin for more accuracy.

I now put 6 sensors in, 3 with the right position in my opinion now, and 3 with the position the other wheel had. That I put in when I first started with my “learning curve”. That way I can learn some things.

Here you can see the loose magnets:





Removing all magnets of the rotor:





Clear view on the stator:




Preparing the hall sensors: (I use TLE4905 )





Finding the right position for the hall sensor:





What I think would be better (NOT):





All wired up:



Edited 2020-05-07 05:21 by nickskethisniks
 
nickskethisniks
Senior Member

Joined: 17/10/2017
Location: Belgium
Posts: 159
Posted: 07:29pm 06 May 2020
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Ok when it was all put back together...

I had fun finding the right phase for the right hall sensor. Especially because I swapped 2 hall sensors in the 2 sets… Turns out, the hall set that I thought were right weren’t so I kept the old position. So the wheels are turning again, both have about the same no load current (+-5A, so +-100W of losses).

I tested with great success, I was a bit rough sometimes @ the throttle sticks although everything was fine now, the mosfets are getting hot to the touch. So I need to mount them on an actively cooled heatsink, or just a bigger one. Maybe I go to more parallel mosfets in the future, but for now I'll stick with 6 single mosfets/controller. So all I need to do is make a new controller pcb with all stuff combined to have a smaller footprint. And less messy!

Mowing performance is good, but I mis a few rpm’s, the motor is now getting about 2200rpm with a 24V battery. But you hear and feel the difference between a fully charged (28V) and a more empty battery @ 24V. I think about 3000rpm will be optimal. So I still need to go to 48V, but that was the plan on the beginning. Not sure if I will power the motor controllers with 48V, that is way to high for my aplication. I limit the speed already in the software with 24V and I only have a 8 bit output.


Although it’s good it’s not good enough for me, the mowing deck needs some further adjustments, it’s not level. The back of the deck needs a proper mounting system, and not those griptie’s. The front of the deck is hanging on a horizontal M14 threaded rod, on the side there are plates with 4 holes, so there are 4 base heights, Simple.

I’ll need to sleep about it for one night, I must remember to make it interchangeable with my sit lawnmower as well.
If I hit an obstacle it needs to go back a bit and go up to minimize damage to the construction.


And last the powered wheels are slicks so not the best on grass, but they could use more weight on it to have more grip. It could be easy because I can position the battery more to the back of the thing.


Hopefully my wife will give me some extra time, because need it with all my never ending list of projects...
 
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