Made a 4x4 Lego RC Car...without Power Functions!

[Crtlego]

So its not purely Lego..

..But for my robotics class at my high school (and just out of fun), I put together an RC set that consists of a laser-cut Arduino remote control and a Lego 4-wheeler that has all-wheel drive and all-wheel steering. That's where things start to stray from what most have done with their Lego RC MOC's: it doesn't use Power Functions. Instead, the entire car is driven by four hobby servos--two regular one (180 degree turning) and two continuous (full rotation) ones. And instead of using a Power Functions IR Receiver, I used two XBEE radios. To control everything on both the receiver and the controller end, Arduino Leonardo microcontrollers are used. These are handy little boards that make for a lot cooler projects than anything the NXT can offer.. but don't take my word for it..Here's a video!

I also have an article about the construction process of both the controller and receiver on Instructables.com (http://www.instructa...-Control-and-L/)

Compared to designing the remote control from scratch and programming everything, the Lego part isn't that hard. The front and rear axles I used (they're identical) had been in development for a while as a part of my effort to develop a more robust and compact drive system (and just happened to be near completion around the time of this project) so the only thing I had to make were the modifications and chassis necessary to house the servos.

Despite my use of non-Lego electronics and servos (and the Lego PF wire I had to cut to use the PF battery box), I consider myself a Lego "purist." That being said, it took some tinkering before I got the servos to fit nicely. I was able to do it rather well in the end with the right positioning of the small blue or gray pins, but it does require you to design the chassis around the motors (at least the motors themselves don't take up that much space).

The next challenge Lego-wise was attaching the rotating part of the servos to the axle. I did this with the original servo mounting kits and a Lego cog or wheel (as long as you have that hexagonal orientation of holes around an axle-hole any part works).

As far as performance goes, I'm glad I experimented with Arduinos and XBEE radios. Its not as convenient a setup as Power Functions, but, besides the great feeling of designing the whole thing myself, it does pay off to be able to customize everything, and to have tons of inputs and outputs (unlike what we are used to).

[tbird8057]

I bet that impressed you teacher. Great job!

[Dorino]

Epilepsy after watching movie :)

[piterx]

ahhah i agree with dorino XD

but hell yeah man! good job...to me all that eletronics is japanese lol

[DLuders]

@ Crtlego: I like how you have integrated Lego Technic and Arduino -- that's what the MINDS-i System attempts to do with Lego-like components. Lego Mindstorms is meant to be a bridge between toys and realistic robotics, but it may not be as fun as directly "driving" your own creation! I would imagine your RC components don't have the range limitations that Lego Power Functions (PF) elements do, or the problems with infrared signal interference from the sun. Are the RC components significantly more expensive than comparable PF elements?

[Crtlego]

I bet that impressed you teacher. Great job!

Thanks!

and I sure did

Epilepsy after watching movie :)

I know!!

Maybe I should put a warning in the video..

ahhah i agree with dorino XD

but hell yeah man! good job...to me all that eletronics is japanese lol

Thanks! And don't worry, I get the feeling sometimes too..

@ Crtlego: I like how you have integrated Lego Technic and Arduino -- that's what the MINDS-i System attempts to do with Lego-like components. Lego Mindstorms is meant to be a bridge between toys and realistic robotics, but it may not be as fun as directly "driving" your own creation! I would imagine your RC components don't have the range limitations that Lego Power Functions (PF) elements do, or the problems with infrared signal interference from the sun. Are the RC components significantly more expensive than comparable PF elements?

Thanks David! Yes, the Technic and Arduino combination has been something I've wanted to do for a long time.. but it was not until recently that had the resources and opportunity to try it out. I must say I do like the two together..

I had seen the MINDS-i System and liked its "heavy-duty" approach and its integration of more "standard" electrical components, but my love for Lego prevented me from even looking into it deeply

And you're right about the increased range. Since they are RF and don't work on IR like the PF elements do, they have really great range and perform in conditions you wouldn't even consider trying to use IR in. I haven't done rigorous testing (maybe I should--if I do I'll let you know), but I've heard that the XBEE models with external antennas (the one on my remote has an integrated antenna while the one on the car has an external antenna) can perform so well that they can be used on RC planes and quadcopters!

As for cost, the radios are a bit more expensive depending on which model you buy. They only vary by $10 or so and the cheapest model is only a little bit more expensive than a PF IR receiver, but since you would need at least two to get started and a couple of other components if you want to attach them to a breadboard or configure different settings through the serial ports on your computer, it easily becomes 2 or 3 times the cost of a PF remote control and recceiver.. Good thing I have these parts on loan from school

[chorlton]

I have a raspberry pi but have often thought about getting into arduino programming.

Do you have a rough breakdown of the cost of the non-lego components? Arduino, XBee, servos, etc.

[aqaz]

Despite my use of non-Lego electronics and servos (and the Lego PF wire I had to cut to use the PF battery box), I consider myself a Lego "purist."

Really?

[Doc_Brown]

great project! :thumbup: I like the editing at the start but not the flashy stop motion, (feel sick) haha

Good luck with the competition.

[Crtlego]

I have a raspberry pi but have often thought about getting into arduino programming.

Do you have a rough breakdown of the cost of the non-lego components? Arduino, XBee, servos, etc.

Strange. I have an Arduino but have often thought about getting into raspberry pi Do you like it?

Prices obviously vary a few dollars depending on the exact model of the components and how you purchase them..

but you'll probably end up with something like the following-its not exactly cheap.

Arduino .. $25-30 (and to get a two-way thing going you would need two boards..)

Standard Hobby Servo .. $10-20 (x4)

XBEE .. $20 or $30 each (and you would need two..)

XBEE breakout board .. $2-3 (you would also need two..)

Wire.. $2-3

Breadboard.. $3-10

The ability to not suffer after cutting a Lego PF wire.. priceless

Optional: XBEE to computer board for configuring beyond factory settings..$25

For my remote control the price of the other electronic components (so everything minus the XBEE and Arduino) is at least $50..

Yeah so to get started you're easily paying the equivalent of a new flagship technic set or more..

..But you can also think of it this way: its better than paying for the NXT!

Really?

So maybe I'm not the purest purist, but yes, really.

I say that because every other time that I build with Lego...I'm building just with Lego and building it with the proper techniques-no bending, stretching, improper spacing etc.

With this build, it was not meant to be a Lego.. it was built as a platform for an electronics-based project. Even so, I still use the proper technique. I could have used anything to power the car.. it didn't have to be Lego and I didn't have to cut the PF wire, but using a PF battery box meant I could mount it on the car with Lego pieces only (if I had used something else I probably would have had to use non-Lego straps or adhesives )

great project! :thumbup: I like the editing at the start but not the flashy stop motion, (feel sick) haha

Good luck with the competition.

Thanks!!

And sorry about that flashiness..

My brother told me the same thing and I agreed, but I had already produced most of the video before he did so I didn't go back and change it

(due to the timing with the competition, it was my quickest production to date)

[timslegos]

How do the non lego motors perform in comparison to an xl or other pf motor?

tim

[Crtlego]

How do the non lego motors perform in comparison to an xl or other pf motor?

tim

Hey Tim!

I haven't done any speed tests or direct comparisons (yet), but if my recollection of the XL motor is any good, the servos are roughly on par with it. I think the XL might be faster, but they both seem to have the same torque.

...maybe Philo has done some tests?

[chorlton]

Strange. I have an Arduino but have often thought about getting into raspberry pi Do you like it?

Yes but I've not done any GPIO programming yet. Media Centre, VPN Host. Learning "Linux from Scratch". i'm mostly interested in the software side. I think the Arduino will always have it beat for this kind of thing. (Although the new beagle black boards look interesting)

Cheers for the info.