Lawnmower project

First off I am a complete noob. I have an Arduino and made an LED blink and fade so keep that in mind.

I have a little bit of programming experience. higher level languages.

I have very little electronics experience. Can read a resistor.

I want to make a remote controlled Lawnmower / ice fishing shanty mover. I know! "What?" -- In the summer I want to push/pull my mower around and in the winter I want to push pull my ice fishing Clam Shell hut around on the ice.

Lawnmower -- I have a push mower to tear apart and use.
Motor -- I have an old three wheel scooter(older than the ones you find at stores etc.) It has a working 24 VDC motor (don't know the amps) It also has a 12VDC type of magnetic brake - I think. If I apply 12vdc to the one wire it releases the brake. If I apply 12vdc (I don't have two batteries yet for 24VDC) to the motor it moves the one wheel. The electronics on the scooter (controller) are fried or at least don't work.

The cool thing about the scooter is that the platform (seat, foot rest, front wheel, steering pole, etc.) is removable which leaves just the motor attached to a 1" square metal frame with a short 4" piece sticking out the front that goes into the front part and is secured with a pin. I think it was designed to be taken apart into two pieces to put in the trunk of a car for transport. It seems powerful enough for what I want to do.

The Idea:

1. So here is the idea that came to mind. I don't want to destroy this thing but rather hook up the Uno to it to control it (eventually from my iPad/iPhone) you know; forward, reverse, stop, speed. Then after I get motor control I want to drive it around sitting on it. Next, I want to build a 1" metal receiver to hook it to a push lawnmower. and drive that around. Lastly, I want to unhook it and hook it to my ice fishing shanty which will also have a 1" receiver as well.

A regular all around helper bot with controls I know how to use. This seems the easy part.

The Hard Parts:
2. For the Mower and unmanned riding I want to come up with a way to steer this thing. So I am researching gears and motors etc. I do have a cordless screwdriver to tear apart first and see if it has enough torque to turn a gear (forward/reverse) and if it is sensitive enough to gain good direction control. I think the screwdriver has variable speed so I think it is slow enough.

3. Once I have steering I want to look into unmanned or at least remote control. Being familiar with a Roomba i.e. (The "it doesn't know where it is, it only cares if it bumps into something and the sensor tells it to back up and turn slightly and try again" part.) I know it does more than that to cover areas decently but for now I just want to emulate that part.

3a. For unmanned control I was thinking of four posts to quadrant off an area with some type of beam (light, laser, sound, etc.) then when the mower hits the beam it stops and reverse x amount of time/distance then turns and tries again until it has free movement. I will start out with squares for now so that this is simpler. In effect using the beams as the bumpers/sensors.

3b. For remote control I was thinking of video fed to my iPhone/iPad and then I can steer it myself from in the house. I actually suffer from heat intolerance severely and can die if exposed too long to the sun in hot weather so this would be great to cut the grass from an air conditioned environment. So far I know that the remote control can be done with some combination of OSC and maybe xBee or something for controlling and I thought I saw a video board but haven't researched that yet.

So, I really would appreciate any suggestions on number 2 and 3a. I'm going to document each step of this project. Even though I think this is a lot to shew on being a total noob I am not duanted by the task and plan on doing the best I can to reach all of these goals.

Any help and suggestions are greatly appreciated.

Tom
:o

Wow, Tom! you are ambitious. looks like you'll have a lot of fun.

Do you have a way to fabricate parts, machining, welding, etc?

I can tell you I started with similar skills about 1 year ago and have progressed some but nowhere ready to tackle something as big as what you are doing. I bought a few reference books...my favorite so far is Electrical Engineering 101 by Darren Ashby. This book plus what I have learned online and from Electrical Engineers in my office.. .is what I have to go on so far.

My guess is that your cordless screwdriver will not come close to the torque you need. sorry.. i am trying to think of an alternative and nothing comes to mind immediately. I think you would want to do a lot of research before committing to which parts to use.

Remote control of a power lawnmower, what could go wrong with that! ;D
Kidding aside, good luck with your project.

Lefty

First off I am a complete noob. I have an Arduino and made an LED blink and fade so keep that in mind.

Well, you're off to a good start!

I have a little bit of programming experience. higher level languages.

That will come in handy!

I have very little electronics experience. Can read a resistor.

Then you'll want to get some; I recommend picking up a copy of Grob's "Basic Electronics" (some older edition, this is a textbook, and new editions can be expensive); its basically the book for EE101 type courses. Plenty of explanation, theory, math, and practical use regarding, well, "Basic Electronics". Starts with "what is an electron" and moves from there.

I want to make a remote controlled Lawnmower / ice fishing shanty mover. I know! "What?" -- In the summer I want to push/pull my mower around and in the winter I want to push pull my ice fishing Clam Shell hut around on the ice.

Ok - not to dissuade you, but what you are about to try to build will not be an easy project; really its not a beginner's project, but if you are willing to take some time on it, you likely can do it. Realize that you will be working with powerful motors, and batteries that can pack a punch, so you need to think "how can I prevent this thing from going out of control"; think manual kill switches, heartbeat monitoring, watchdog timers, and dead-man switches. Realize that you need to design this up front, before any of your other control systems, if you want this to be somewhat safe...

Also - in addition to the above book, I could also recommend a host of robotics books that could help you along the way...

Lawnmower -- I have a push mower to tear apart and use.
Motor -- I have an old three wheel scooter(older than the ones you find at stores etc.) It has a working 24 VDC motor (don't know the amps) It also has a 12VDC type of magnetic brake - I think. If I apply 12vdc to the one wire it releases the brake. If I apply 12vdc (I don't have two batteries yet for 24VDC) to the motor it moves the one wheel. The electronics on the scooter (controller) are fried or at least don't work.

Ok - if you plan on having any kind of PWM speed control of the drive motors, you will -have- to buy a motor speed controller. For your motor, you need to find out what its current needs are for stall current (shaft locked) and running current (free shaft - also called a no load current; this would be the motor only). Hopefully there's a sticker or something on the side of the motor that gives this information; you need to find this out.

You will want to size your motor controller to be at least (plus 10-15 percent) the size of the greater (stall) current needs. Say the motor stalls at 100 amps; you would want a controller that could handle around 110-120 amps. Hopefully your motor won't pull this much - high-amperage controllers are not cheap (neither will the batteries) - for instance:

(note that I have no stake in this company, nor have I ever ordered from them - its just an example; I encourage you to do your own research on motor controllers)

Depending on the amperage requirements of the motor, you may be able to use relays to control it, provided that the "top speed" isn't anything crazy (because with relays you can't really control the speed of the motor); the relays you will need to use will once again depend on the current required by the motor - this will determine what the relay's "contact rating" will need to be. Hopefully you can find 12 volt relays that will work, but if not, you could get larger 24 volt DC contactors (if you need to handle a LOT of current).

Regardless of the controller, you will also need to design the power distribution system; you'll need to take into account how much power the motor uses, plus whatever you use for steering (more on this below), plus whatever for the controller system (the Arduino and anything else - though compared to the other parts of the system, this will be tiny; figure 2-5 amps max). Once you know this, you'll be able to size your battery.

You will want an inline-fuse/breaker for the whole system, and if the 24 volt system is two 12 volt batteries in series (likely), you may want to have both a 12 volt rail and a 24 volt rail, along with your ground rail. Use bus-bars for AC circuit-breaker cabinets, and color code with dabs of paint on the ends (you might also want to match color coding with your wires; it will help immensely to sort future issues). From the rails to circuits, add secondary inline fuses/breakers.

The cool thing about the scooter is that the platform (seat, foot rest, front wheel, steering pole, etc.) is removable which leaves just the motor attached to a 1" square metal frame with a short 4" piece sticking out the front that goes into the front part and is secured with a pin. I think it was designed to be taken apart into two pieces to put in the trunk of a car for transport. It seems powerful enough for what I want to do.

Once again, please realize that this power can cause bodily or property damage should it go out of control; please think about your safety/recovery system first, before anything else. This is one piece of the puzzle that many people neglect until after they need it (or until the end of the design), at which point it is very hard to put into place in an already running system (this is true for just about any system you can think of, hardware or software based, by the way!).

The Idea:

1. So here is the idea that came to mind. I don't want to destroy this thing but rather hook up the Uno to it to control it (eventually from my iPad/iPhone) you know; forward, reverse, stop, speed. Then after I get motor control I want to drive it around sitting on it. Next, I want to build a 1" metal receiver to hook it to a push lawnmower. and drive that around. Lastly, I want to unhook it and hook it to my ice fishing shanty which will also have a 1" receiver as well.

When testing this thing, once you get it to the point of rolling, I recommend you start with "wheels-off-ground" to verify the operation of all systems (including all safety systems) as you work on and debug your code. Doing so will help prevent unexpected surprises (which may still occur - which is why you build in the safety systems first).

A regular all around helper bot with controls I know how to use. This seems the easy part.

;D

The Hard Parts:
2. For the Mower and unmanned riding I want to come up with a way to steer this thing. So I am researching gears and motors etc. I do have a cordless screwdriver to tear apart first and see if it has enough torque to turn a gear (forward/reverse) and if it is sensitive enough to gain good direction control. I think the screwdriver has variable speed so I think it is slow enough.

Unlikely, but you can try it; you'll probably strip any gears it has, unless it has a clutch mechanism of some sort. My advice would be to cut your losses now, and buy a linear actuator (with whatever extension length needed to move the front wheel in the full left-to-right arc) - for instance:

Remember that you may have to either buy one with limit switches, or implement limit-switches yourself to prevent end-of-travel jamming; you may also want to get one with a built-in potentiometer or other sensor to determine where along the length of travel the actuator is (and hence, what direction the steering wheel is pointed, thus the angle of turn).

There are other options available (Servo City has some interesting geared systems), but really a linear actuator, or some other kind of heavy duty geared motor and transmission system is going to be needed.

Had to break this up - I'm writing a novel here!

;D

Regarding the steering motor (and needed controller): It shouldn't consume as much amperage as the drive motor, but it may, so keep that in mind so you can build or buy the controller needed.

Something else: Why am I telling you to buy motor controllers? Because you don't have the skills yet to build such controllers (neither do I!) - and you likely waste more money trying to build one (and learning the hard way) versus just spending the money on a controller. Fortunately, a controller for the steering motor or linear actuator likely won't need to be as beefy as the one for the drive motor, so there's that. But you need to be aware of the specs of the motor (stall/running current needs), and design accordingly.

3. Once I have steering I want to look into unmanned or at least remote control. Being familiar with a Roomba i.e. (The "it doesn't know where it is, it only cares if it bumps into something and the sensor tells it to back up and turn slightly and try again" part.) I know it does more than that to cover areas decently but for now I just want to emulate that part.

You said you were going to tow the mower behind the 3-wheel scooter, right? Have you thought about how you would get such a thing to back up properly? Unless I am misunderstanding you, you are going after a trailer-style linkage, right? So to back up, you would have to somehow get the robot platform to understand how to "back up a trailer", just like a driver would...

If you can figure out how to automate that, you will have an invention worthy of the name!

3a. For unmanned control I was thinking of four posts to quadrant off an area with some type of beam (light, laser, sound, etc.) then when the mower hits the beam it stops and reverse x amount of time/distance then turns and tries again until it has free movement. I will start out with squares for now so that this is simpler. In effect using the beams as the bumpers/sensors.

This probably won't be reliable to detect or such, or you will have false positives, or you will need some kind of interface from the beam-break (RF or such) to the robot. I understand what you are trying to get at (ie, getting the robot to "see" or "hear" the beam of light or sound it is "breaking"), but such a scheme likely won't be reliable...

I would instead suggest a buried or staked-down perimeter fence wire, which you run a modulated and coded signal through using an amplifier, the output of which can be picked up by the robot. One of these:

...suitably hacked could certain work, and its cheap enough.

Alternatively, you could bury magnets spaced so far apart along the perimeter, then use a hall-effect sensor to detect them...

3b. For remote control I was thinking of video fed to my iPhone/iPad and then I can steer it myself from in the house. I actually suffer from heat intolerance severely and can die if exposed too long to the sun in hot weather so this would be great to cut the grass from an air conditioned environment. So far I know that the remote control can be done with some combination of OSC and maybe xBee or something for controlling and I thought I saw a video board but haven't researched that yet.

I would actually use something like 802.11 wifi - something like this Arduino:

http://www.robotshop.com/productinfo.aspx?pc=RB-Asy-02

So, I really would appreciate any suggestions on number 2 and 3a. I'm going to document each step of this project. Even though I think this is a lot to shew on being a total noob I am not duanted by the task and plan on doing the best I can to reach all of these goals.

Any help and suggestions are greatly appreciated.

Though it may not seem like it, I have barely scratched the surface of what this project is going to entail for you to build, at least properly for a safe operating device. Given its size and what you plan on doing with it, plus the need/want for remote control, I once again want to impress upon you the importance of a safety system. The last thing you want is a small child or dog running into this machine's path, and having no way to stop it.

With that said, there's a lot to do here, if you want to do it right without throwing good money after bad. It won't be cheap, but at least you have the most expensive part out of the way (the scooter - I'm sure you know how expensive they can be, even used). Take your time on the project, design, plan, and build one component at a time, and it should work out. I would also suggest bench-testing using smaller components and/or "stand in" systems; if you can build a model of the system (maybe a scaled down version), it might help to work out some of the control system bugs without danger of injury or other destruction while testing.

Good luck, and I hope it turns out successfully for you!

heartbeat monitoring

OH PLEASE!!!
Of course you should have a safety system in place especially with something with a spinning blade but you, me and the OP know that such a device would cause more harm then good (false readings, complicated implementation).

(because with relays you can't really control the speed of the motor);

This is false.
I have PWM'd relays to control motor speed.
It works ok but its noisy and the speed control is alittle rough.
Other then these, the advice is sound.

FWIW Sending video over wireless with arduino sounds challenging.

You may want to search the forum for lawnmower to see previous post on similar projects.

OH PLEASE!!!
Of course you should have a safety system in place especially with something with a spinning blade but you, me and the OP know that such a device would cause more harm then good (false readings, complicated implementation).

First off - this doesn't sound like the OP's going to use a deck mower, but rather an old-fashioned push mower (manual mower, no engine/motor) dragged behind.

Furthermore, it is better to have false readings than damaged property and/or bodily injury. A machine this size can and will cause harm if it is not properly controlled. A safety system can and should be built as part of the initial design.

You can be cavalier about it, but I consider safety in such larger-scale robots (and this is a larger scale robot) to be paramount. It's nothing like an SRL robot, surely, but you should have at the very minimum some kind of manual on-board cutout switch, as well as a remote-controlled one. Such as system is cheap and easy insurance.

Quote:
(because with relays you can't really control the speed of the motor);

This is false.
I have PWM'd relays to control motor speed.
It works ok but its noisy and the speed control is alittle rough.

You might be able to get away with that on small motors, but I think at the size motors being discussed (power chair motors), you would quickly wear out (or weld the contacts - but we have a safety system in place for this, right?) the relays in short order due to arcing.

FWIW Sending video over wireless with arduino sounds challenging.

I would hope the OP isn't planning on having a first-person view camera on this thing; line-of-sight operation should be the plan, with constant monitoring while in operation, in case of any possible hazard (the proverbial child or small dog) that gets in the way - then the "all-stop" system can be activated.

This isn't paranoia - this is proper system design for a device of this nature. Take all the shortcuts you want, of course; I am only making recommendations based on "best practice" for safety. Note that in the overall cost and complexity of the system, trying to save a nickel (and time) by not implementing such a backup seems foolhardy to me, at best. YMMV.

I am not saying safety is not VERY important.
I am just saying a heartbeat monitor is guaranteed not the way to implement it.
It is not the normal way to monitor safety and is plain inaccurate.
Set too low and the excitement of trying it shuts it off immediately, set too high and its useless.
FWIW, You should have a LARGE relay on the main power to the motors and in case the safety system is triggered, it will kill all motor power even in the event of the relay or mosfet controlling the motors short.

hmmm heartbeat monitoring is of the machine, not the person, correct?

good idea. I did an investigation of my car's cruise control module last year and it has such a device. the premise was that if the computer's clock stopped oscillating, it shut the system off... rather than leave the accelerator pedal pressed or worse yet 'accelerating'!

I am not saying safety is not VERY important.

Good - we agree!

I am just saying a heartbeat monitor is guaranteed not the way to implement it.
It is not the normal way to monitor safety and is plain inaccurate.
Set too low and the excitement of trying it shuts it off immediately, set too high and its useless.

Something that I didn't make clear in my post was that the suggestion of "heartbeat monitoring" was something to be investigated (along with the other items), not that it was necessarily needed; only the designer/builder could determine that. If the OP were only using a single controller (aka Arduino), then it wouldn't help. If, however, multiple controllers were used (say separate ones to monitor/control steering and other functions), then some form of "heartbeat" or check between the controllers could help to determine if one or more have failed, and if so, activate the "full-emergency-stop" functionality.

FWIW, You should have a LARGE relay on the main power to the motors and in case the safety system is triggered, it will kill all motor power even in the event of the relay or mosfet controlling the motors short.

That's a good idea; ultimately it will be up to the OP to determine how far to take the safety system, depending on where and how the device is planned to be used (and the level of supervision given to it).

@mk3 -- Thanks. I do have both an oxy and mig (metal sculpture). I will check out the book 101. Thanks for that. research - will do.

@retrolefty -- Yeah! That's what I thought. But then nobody died with the hovercraft project but it did sink into the river. Should have tried the lake first. But that's another story.

@cr0sh -- Thanks so much for all of your ideas. I will do my due diligence first and of course I am researching now. Manual unkillling switches, got it. check. ;=) seriously, as i progress I plan to draw up plans, hack a little, research, draw up more plans so I will be asking alot of questions as I progress this spring and summer.
I will start with the motor and research that thoroughly - good point. Actually there may be working parts on this scooter that are not fried so I will use that as a starting point to get an idea of what 'was' used to control it before. I will also ry to plan from the beginning a safety system. In fact That will probably be my first set of questions as I research this.
Wow, you really have given me a lot of advice. I have printed out your reply and have read through it a couple of times and I'm sure I will again as I proceed. (12vdc 24vdc rails and such with paint dabs, inline fuses, etc. - good ideas).
Actually, this may be a push and/or pull thing but I have to see how much wait it can push first. 'IF' things get to the point of backing up the shaft will make this connected to the mower/fish sled and not a tongue system like a trailer. so I was thinking it would be 1 turn wheel 2 reverse motor for x time 3 turn wheel 4 forward motor etc. rinse and repeat until sensors are not getting triggered. We'll see, hopefully by then I will know a lot more.
CABLE TRACKER ! yes that seems probable.
Thanks again for 'bringing me down to earth' as it were and I agree safety has to be my first order of business and throughout this project. That said, I am almost giddy with the thought of this maybe working. It has been a long time dream of mine to tackle something like this.

Lastly, as for video, I have a half dozen wireless cameras and as such can monitor this from first person, third person, and across the yard as well as from the roof of my house. I live in a semi secluded area with an acre of 'grass' to cut. I have in the past hooked up my video cameras to RC cars and had a track outside and my friend and I inside racing around the track on TV so I know how hard it is to do it that way but it was great fun. This project is completely different and of a scale that that would be dangerous to attempt and I do not expect to do that here. But video would be very cool, none the same.

Off note: I did consider that this might work best with more than one Arduino controlling each system. And the idea of monitoring the whole system seems prudent.

Good ideas all.

I will post/ask as I progress and judging from the responses so far I think this is the perfect forum to proceed with.

Back soon....

Tom

Maybe this would be easier.

Well, life just got easier (harder?). I just bought a used Roomba with a bad battery. Bought a new bat on ebay and it is fully functioning. SO, I already can control the Roomba via IR from my Mac using irTrans and iRed2. Very cool but limited control. The next step is to hook up the Arduino to the Roomba via the Roomba's serial port.

Then it looks like more control and responses from the roomba's sensors and fully autonomous as well (with bumber control and maybe converting the cliff sensors to another sensor type). Now if I can find either a used electric wheel chair or some very cheap motors I can replace the connection to the roombas wheels with the bigger motors and I should be half way there.

Roomba Brain with Arduino Controller. Then maybe OSC via iPhone to Xbee or something...

More as i collect more hardware...

Very cool.