Robot chassis

Im trying to build a robot, i have and arduino board already so i need a chassis, wheels and motor… where can i buy this as a kit?? that will work with the arduino board… Thanks :slight_smile:

btw i like this one: http://www.makershed.com/ProductDetails.asp?ProductCode=MKOMT1 alooot but i dont really want to pay that much… is there something like that that includes the acrylic, wheels and motors for alot cheaper??? thanks again

when i messed with it, i would just go down to the local rc hobby shop and load up

still expensive tho

i live in tampa, FL we dont have an RChobbyshop here :frowning:

maybe something like this : http://superdroidrobots.com/shop/item.asp?itemid=484&catid=68 umm but not sure

No experience myself, but saw this link a while back:

Seems to have pretty wellpriced motors, gears, wheels etc.

will this combination work with the arduino: http://www.pololu.com/catalog/product/114 + http://www.pololu.com/catalog/product/64 ??

Not directly - you can’t run motors directly off the arduino digital pins.

Luckily there are motor shields like ladyada’s designed to do just this!

Also you’d need some sort of chassis to hold the arduino + gearbox - tamiya make one that is designed to mate with the gearbox, andd you can use two of the holes in the arduino to also mount it to the chassis.

Do you have access to a band saw or similar? Make your own chassis out of wood! Obviously, it’d be best to buy the wheels, but you should be able to get those cheaply.

you taking abut this one: http://adafruit.com/index.php?main_page=product_info&cPath=17_21&products_id=81 ??

which wheels and gearbox you recommend?

Your link is improperly formatted - there is an extra “h” at the start.

But yes that would be an appropriate shield.

fixed…

btw which wheels and gearbox you guys recommend?

SuperMiguel,

I have had good success using the Tamiya Twin Motor Gearbox and Track and Wheel Set to build simple robots (see links below):

http://www.tamiyausa.com/product/item.php?product-id=70097
http://www.tamiyausa.com/product/item.php?product-id=70100

Even if you have only limited access to a shop full of tools, you could use a simple (inexpensive and easy to cut) piece of thin hobby plywood or basswood that should be available at your local craft (e.g. Michael’s) or hobby store.

Here is a video of a robot that is similar to the one that I built:

Additionally, there was a very nice (simple) Arduino based robot that included ultrasonic sensing published in Make magazine #17
http://makezine.com/19/makey/

Dig in . . . make some saw dust then type some code and have some fun!

and to turn they one use one motor right?

I made my on chasie out of pelxiglass, it was really easy to work with, I cut the wheels on a router table and made the servo mounts with a dremel in the router base. I used 2 continous rotation servos for the drive wheel’s and I have 2 IR sensors to avoid objects and 1 to keep it from driving off the edge of a table. It’s also set up to light led’s when objects are detected. I’m still working on the code as I’m not very good at coding. The whole project has cost around $100 US dollars. I hope this helps…

If you want a really cheap chassis, go down to your local thrift store (here in the US try Goodwill) and find an old radio-controlled car/truck/tank/etc - real easy to find, and you shouldn’t spend more than $5-10.00 (US).

Before you buy it, make sure everything seems mechanically sound from the outside:

  1. Turn the drive wheels slowly and listen to the gearbox (don’t turn the wheel fast, you can strip the gears) to make sure it sounds good. Rotate the drive wheels fully a few revolutions to ensure that there isn’t any stripping of the gears (the wheel will slip or “freewheel” if there is).

  2. If the vehicle uses a differential drive system for the driving wheels, remember to lock up one side, turn the other, then lock that side, and turn the other - to check all parts.

  3. If the vehicle uses Ackerman steering, check to make sure that the servo or whatever it is using seems like it works (stay away from the real el-cheapo models that use an electromagnet or such to click-clack the wheels back and forth). If it seems too loose or broken, you may want to pass on it (unless you think you can fix it by using a cheap hobby servo).

  4. Don’t worry if it doesn’t come with the remote - you won’t need it.

Once you decide on a device, and bring it home, you’ll need to put on your hacker’s hat. Carefully open it up, and inspect everything again. If you can, clean and re-lubricate the gearboxes and such (use something like SuperLube or in a pinch, petroleum jelly).

Find the wires from the motors and/or servos and trace them back to the control board. On that board, for the drive motors (and perhaps the steering servo/motor), near where the wires enter the board, you should find them connected to a series of small transistors (or if you are lucky, a darlington transistor array like a ULN2803); basically, these transistors will form (in some manner) an H-bridge (unless you get really unlucky and happen upon a drive scheme like they used in the old Milton Bradley Big Trak - it was some weird two transistor half H-bridge scheme that split the battery box in two; probably saved them a ton of money in manufacturing, though); you’ll want to lay out a schematic for what you find.

Once you have a rough idea of the schematic (the inputs and outputs of the bridge, power, and ground), try hooking up some batteries to the vehicle; then attach a separate 5-6 volt DC battery pack in parallel to act as a “signal source”, and touch the positive wire lead (the negative is hooked to the chassis ground) to the input (base lead bias resistor) of the suspected H-bridge; if all goes well, it should spin the motor in one direction.

If you get lucky, no magic smoke will be lost. If you don’t get anything, no matter what you try, either there is an issue with the circuit, or with the motors; try disconnecting the motors from the control PCB (label the leads first so you can re-connect later if needed), and applying power to see if the motors run. You might find it cheaper and easier to build your own h-bridge circuitry (very easy to do) to drive the motors directly and by-pass the control board. If you do get the control board working, you will want to cut the traces leading from the R/C circuitry outputs to the h-bridge inputs to bypass the circuitry (as well as eliminating other potential problems) - these inputs you would want to buffer (using a hex-buffer chip or similar), then drive the buffer with the Arduino’s digital outputs.

If there are steering servos involved, it is likely that (if it isn’t a cheapo setup) that the servo feedback system is “on-board” the R/C control board; I wouldn’t bother trying to figure it out (its possible, but it could be a nightmare, especially if you don’t understand how a servo feedback circuit works) - instead, hook into the h-bridge or build your own like above, then take the feedback potentiometer and run it to one of the analog inputs on the Arduino. As you control the motor for steering, check the analog values (ideally, you would set up an interrupt on these pins, and check it that way), and when they match up to where you want the angle to be, stop the motor. Alternatively, you could replace the system with a hobby servo. Cheap hobby servos can be found here: http://www.hobbycity.com/hobbycity/store/uh_index.asp

All in all, the idea is to repurpose that which has already been built; this kind of system can (and should) be scaled up as you go along (the same techniques can be used to control a PowerWheels, a small quad, or even a full-size vehicle; of course the control system gets a lot more complex the bigger the vehicle involved, not to mention the safety systems).

I hope this post helps you out!

the same techniques can be used to control a PowerWheels

Oh dang! I have an old PowerWheels in the garage. Hmmmmmmmmmm

The thing about a PowerWheels that you have to realize is that the drive motors and the eventual steering motor are both going to pull some serious amperage, especially once you start adding weight.

I am in the process of building a robot based on PowerWheels H2, using a 328 Arduino to act as a controller for the drive and steering motors, and as master controller to a Pololu servo controller (which will be interfaced to servos actuating a custom PT camera/LIDAR mount). I have designed and breadboarded an h-bridge to control the steering gear-motor using 2N3055 NPN power transistors in TO-3 package; properly heat-sinked, they should give me enough current to drive the motor without burning up. For the drive motors (there are two in the H2, one per rear-wheel), I am going to initially use Bosch relays or similar in an h-bridge to control them, until I can know the actual current draw, then I intend to either build my h-bridge drivers, or purchase a commercial unit; most seem to hover around $100.00 for one that can source the kind of amps I am looking for - but if my guess for the amount is wrong (I have a feeling it may be), and after I do some measurements with the entire system on board, maybe it will be on the low side and a homemade h-bridge is possible?

Of course, I still have yet to design the power-distribution system for it (mainly because I don’t know exactly how many batteries I will have on-board; I am also toying with the idea of an on-board gas-powered gen-set)…

http://letsmakerobots.com/start check out part 2 too.