RC Lawnmower Ideas

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ptribbey
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RC Lawnmower Ideas

Post by ptribbey » Tue Feb 23, 2010 7:46 am

Hi all,
I am gathering parts and ideas for an RC lawnmower. The base will be a cheap push mower from the big box home mart. The front wheels removed and big casters installed. I purchased the 12V right and left hand gear motors from All-Electronics. I will either attach a sprocket to the big back wheels and run a #25? chain up to the gear motors, or possibly a cogged timing belt and pulleys. A small 12V LA battery will be charged by an additional coil mounted under the shroud adjacent to the flywheel magnet. (I could use help with optimum coil design also)

I am writing this thread wondering if anyone has used the IR3220S 60 Watt H-bridge? It has tons of features, like overload protection. My favorite!

I was planning to interface a Futaba RC setup to a pic to drive the h bridge. In the past, I have used Bob Blick's indestructible h bridge design from the 'net. Below is a link to the IR 3220 datasheet. A Google search for "RC Lawnmower" turns up a rugged design by Terry Creer.
http://members.iinet.net.au/~tnpshow/RCLM/intro.htm

All comments appreciated.

Paul


IR 3220
http://www.irf.com/technical-info/white ... meur02.pdf

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jwax
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Re: RC Lawnmower Ideas

Post by jwax » Thu Feb 25, 2010 6:56 pm

Save yourself the grief of a gasoline engine. Waste of energy. Electric motors are capable of wacking that 4" grass down to 2" with much less noise, pollution and energy. Plus, it's elegant.
There are many electric-based mowers out there, have been for years. (Mowbot-1970?)
Convert an existing electric mower to RC.
WA2RBA

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Re: RC Lawnmower Ideas

Post by SETEC_Astronomy » Thu Feb 25, 2010 8:47 pm

Are you committed to this being a DIY project or is this a case of I don't care how I get there but I want it? If the latter is true there are several ready made robotic mowers that range in price from $275 to $3000+. The features range from simple bump detection for a fenced yard and you need to keep the batteries charged to bury a boundary wire and self charging loop for hands off operation. Other features include alarms if someone tries to make off with the mower, tilt switch which stops the blades to keep kids (and adults) safe if they attempt to pick it up and timer operation which sets a mowing schedule.

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dacflyer
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Re: RC Lawnmower Ideas

Post by dacflyer » Fri Feb 26, 2010 8:16 pm

i seen a real simple one before somewhere,, youtube probably, it was just radio controlled.
a R/C radio, 3 ch. 2 channels controlled 2 motor controllers. and the 3rd was the throttle/kill
but as you mentioned, you can make it complex also.

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Re: RC Lawnmower Ideas

Post by jollyrgr » Sat Feb 27, 2010 9:05 pm

In engineering school a team of EEs and MEs tried making a robotic mower. It "sort of" worked. Still don't see it on the market.

As far as RC mowers go I've read several designs on these. If I were doing this here is what I'd do:

Gasoline engine for main power. Despite the fact that electric motors can do the job and much quieter, the fuel weight will be too high.

Front wheels, casters like you stated. But go one better. Get a "mobility" scooter, like those for people that have difficulties walking. The electric design is done as far as controls is concerned. The wheels can more than push a mower. To control the speed and direction only requires small servos to move a joystick. The front caster(s) will likely come with the scooter. These are not as expensive as you would think ($150 used) if you don't mind Craig's List or eBay.

As far as frame goes, build something that will allow you to raise and lower the deck lid. Pipe in pipe (either round or square) and pins to hold it in place. Maybe springs to allow for bumps. Or have the pin at the top of the pipe so the mower can bounce up and not bottom out.

Fasten an alternator to the shaft in some fashion so you can go with a smaller battery. Mowers with a self propel feature already have a belt and pulley going to one set of wheels. Just remove the belt from the self propel wheels and cludge in an alternator.
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Re: RC Lawnmower Ideas

Post by dacflyer » Sun Feb 28, 2010 6:45 am

i found a few links on break.com

heres a couple..

http://www.break.com/findvideo/remote-c ... wn%20mower

http://www.break.com/usercontent/2010/1 ... er-1704233

there is some good designs..maybe morph a few to customise what you like..
1st thing i'd do is find a good donar mower with a sturdy frame and a good engine.
you do not want anything thats going to be 1/2 worn out or flimsy or smokes a lot.

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Re: RC Lawnmower Ideas

Post by jwax » Sun Feb 28, 2010 7:31 am

You'll end up with a standard, noisy but wireless dangerous robot with a gasoline engine.
Go all electric. Think energy. You don't need 6.5 horsepower to cut grass.
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Re: RC Lawnmower Ideas

Post by dacflyer » Mon Mar 01, 2010 5:44 pm

hehehheh, have you ever delt with bear grass or bahiya grass ( AKA hiway grass )
that stuff is horrible here..wears blades out fast as if you were cutting in sand.
and bear grass will stall a engine quick..
feels like you need 10HP some days..and you can almost watch it grow..up to 12" a week here if there is no dry spell.. 6" if its really dry.

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ptribbey
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Re: RC Lawnmower Ideas

Post by ptribbey » Tue Mar 02, 2010 11:07 am

Thanks for all opinions.
I was specifically looking for advice on the IR 3220 H bridge IC.
Paul

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haklesup
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Re: RC Lawnmower Ideas

Post by haklesup » Wed Mar 03, 2010 5:45 pm

You don't need 6.5 horsepower to cut grass.
Depends on how long you wait and how fast you move. Since this isn't human operated, mowing at a slower velocity will reduce the HP needed to get the job done without stalling.

Have you considered hacking the control boards from a roomba? Nobody ever said you have to mow in any systematic pattern. Replacing the drive transistors should allow it to power a bigger drive motor. You would also need to craft a larger bumber sensor (and tolerate the mower feeling its way on the edge of the lawn (not great for street frontage w/o a fence)

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Re: RC Lawnmower Ideas

Post by CeaSaR » Wed Mar 03, 2010 7:36 pm

haklesup wrote:Have you considered hacking the control boards from a roomba? Nobody ever said you have to mow in any systematic pattern.
I'd love to see what that lawn looks like after "Lawnba" was done! "Hey, look Fred! Harry's lawn is post modern art! HAHAHA!"

CeaSaR
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ptribbey
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Re: RC Lawnmower Ideas

Post by ptribbey » Thu Mar 04, 2010 9:04 pm

Interesting idea Hacklesup, but I think I will stick with sitting in my lawn chair mowing with the Futaba in hand and mower in full view. - well possibly in a monitor with a camera - .
I will use the venerable Bob Blick Hbridge boards. I've built four of them for various things like my lawn chair that always faces the sun for instance. They are virtually indestructible. I'm working on coding a picaxe 08m for the translator. The motors I bought from All electronics are Denso 12 Volt 730556-7030 and 730557-7030 (right and left handed.) I found bike chain sprockets for both the wheels and motors at my local surplus outlet. The motors are 180 rpm no load. 17/32 ratio on an 8" wheel gets me around 2.25 mph tops (no load) . (95 rpm * 25" circumference)
Should work.
I will post progress. I am buying a new house and moving right now so it may be a while. That is why I'm building this in the first place. My current lawn is around four acres and 2 + hours on the rider. plus lots of expensive gas. New lawn is 60' X 135' and perfect for an RC mower.

PT

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Re: RC Lawnmower Ideas

Post by CeaSaR » Thu Mar 04, 2010 9:20 pm

Radio location and some G code should get you completely automated. I wonder what the resolution would
need to be to get that to work???

:mrgreen:
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Re: RC Lawnmower Ideas

Post by jwax » Fri Mar 05, 2010 3:55 am

Paul- My only concern with those motors is their ability to run in continuous duty mode. Their design is for intermittent duty, and they may not do well in a constant-use mode.
I'm hoping too that the electrical motor noise/PWM switching does not affect your RF control signals. I trust the RF is an encoded digital signal.
Do keep us posted! :grin:
John
WA2RBA

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ptribbey
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Re: RC Lawnmower Ideas

Post by ptribbey » Fri Mar 05, 2010 11:04 am

Jwax,
Of course you are correct on the duty cycle. That was a concern, but I made a jig on my bench and ran one 8 hours with a brake on the sprocket and it seemed to not get especially hot.
These may be a little undersized though. I have been looking at the Futaba website, trying to decide which TX/RX to buy. Digital spread spectrum 6 channel looks ideal, but a little spendy.
PT

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