Hi Dumb question, but here goes...
I need to buy some simple robotics for an Arduino demonstration.
I plan to buy some of these from eBay
But it looks like the kit doesn't come with the drive electonics
I presume that something like this would fit the bill
Or can someone else suggest a better way to source a few of these sorts of things
Note. I have plenty of Uno's, and Mico's and Minis and Mega boards etc, I just don't have the robot hardware stuff
You could make a bot like below using inexpensive servos modified for continuous rotation for the drive motors. Instead of cutting out the drive wheels, use large jar lids, or pie pans from the DollarTree store.
How much money are you willing to spend ?
Those Ebay things might break before the demonstration. You also don't know the stall current of the motors, so the L298N could blow if the robot drives into sand. For demonstration purposes it is easier to use a shield.
Perhaps you can buy a compleet set.
Thanks guys
Budget is low (as low as possible)
Re:Rolly Bot
Very cool, but probably a bit confusing to a lot of people
I’d like to do something more conventional.
Use will be indoors on carpet, so not too much rolling resistance, but if it bumps into something I can see the motor current could be an issue
This is just the 4 wheel version i.e same cheap components but has the Arduino and a Bluetooth, and possible distance sensors, all of which I already have already
I could get the 4 wheel version, but I wasn’t sure about the steering, I thought the 2 wheel version may be easier to program. The 4 wheel one
http://www.ebay.com/itm/4WD-Smart-Car-Chassis-Mobile-Robot-Platform-Compatible-for-Arduino-MCU-DIY-/181329341315?pt=LH_DefaultDomain_0&hash=item2a38122b83
references the same H brdige IC L298, just needs 2 x 2H bridges as each of the 4 motors
Does anyone have any experience of the quality of these 2 or 4 wheel “robot chassis” from eBay etc
Or is it just a question of buy one to see the build quality?
Does anyone have any experience of the quality of these 2 or 4 wheel “robot chassis” from eBay etc
they aren’t that fast and they can be quite noisy.
Probably better off getting a cheap rc, or build one from Legos or an Erector set.
they aren't that fast and they can be quite noisy.
umm.
Thanks.
Noise could be an issue, slow speed, not so much of an issue.
I'll look for some alternatives. I have some NEMA 17 stepper motors for another project that I could borrow for a while, and I have a spare ramps board, but I'd then need 12V and need to get some wheels etc.
Sounds like I need to look for another solution elsewhere.
Thanks
Looks like its a chassis from HobbyKing
Possibly this one
Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking26251__Aluminum_4WD_Robot_Chassis_Black_KIT.html
Looking on HobbyKing I also found a cheaper 4 wheel kit
Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking26250__4WD_Robot_Chassis_KIT.html
and a link to this video
Noise in the video doesn't seem that bad to me
Looks like the 4 motor versions have a lot more zip than the 2 wheel ones. 
I think most of those motors would work with an L293 but the L298 is a better choice due to the higher current. I have a bunch of example sketches I downloaded for both types if you need any. What's the timeframe ?
I need to buy some simple robotics for an Arduino demonstration.
You didn't mention the deadline.
You didn't mention the deadline.
No date set yet, so I, hopefully, have plenty of time to get all the components together, and can buy things online and save myself $$
I think most of those motors would work with an L293 but the L298 is a better choice due to the higher current
Thanks. I'll get a board with L298 . I like a "Belt and braces" approach
Hi Roger,
I’ve build a few robots, nearly all 2 wheeled, their simpler to stear and turn. I even used the ebay bot that your looking at, a bit basic, but does the job. I’m now figuring out how to use the slotted wheel disk to give me a proper 90 deg turn. I also have a tracked Zumo bot and the larger RP-5 chassis that’s sorry not cheap but works well. I have used the L293 it’s not perfect and you loose power in the output transistors, but it’s cheap and does the job, easy to control, etc… My Zumo uses a small DVR8833 driver module that has FET outputs, better power control.
I’ll see what pictures I can post, but if you take a look here: www.melsaunders.co.uk under electronics, you can see my early bots. some build on Vero board.
Hope it helps, Regards.
Mel.
Mel,
Thanks.
The tracked vehicle looks good, but as you know i was trying to go low budget, possibly to buy more than one.
I'm currently thinking of getting one of the 4 wheeled variants, possibly from HobbyKing, but I"m also going to take a look in the local toy stores and places like KMart etc, to see what they have and whether it would be modifiable (probably not)
Cheers
Roger
From what I've seen, modifying the inexpensive rc toys is pretty much a no go. Also, most rc vehicles are made to go too fast to be made in to useful bots.
edit: I've ordered a rebuilt netgear 614 router to pick back with my router bot project below. Something similar might make an interesting class project for an inexpensive networked bot.
modifying the inexpensive rc toys is pretty much a no go.
Why is that? That’s what I did to my RC truck and as far as the speed, you can control that easily with PWM.
But if you want to add things to the RCs, then yea, its a pain in the butt. But if you just want to mod the rc to work with an Arduino, just for fun or to say that you did it, then it is very easy.
I personally prefer to make my robots by hand, from Legos or an Erector set, just so if there is something I want to change or add to it, I can. This also allows me to be creative with the designs too.
Right now I am building a hollow wheel motorcycle with Legos. I am finished with the design, and now I just need to figure out the placement of the electronics. I do still need to work out how it will balance itself.
HazardsMind:
modifying the inexpensive rc toys is pretty much a no go.
Why is that? That's what I did to my RC truck and as far as the speed, you can control that easily with PWM.
I'm kinda curious on this, too - especially since some people have managed to control their RC cars by emulating the output from the receiver (the pulse code provided by the transmitter) - on RX2/TX2 and variant chipset cars:
http://forum.arduino.cc/index.php/topic,86883.0.html
The only thing I can think of that would be objectionable is that on some cars, it can be difficult to find proper solder points, and that some use lower voltages and whatnot for the control of the on-board h-bridge drivers. As such, it can be easy to blow them rendering them useless. There's also the fact that you don't have proportional control of the steering in most cases, either (this could be rectified by substituting a real RC servo for the existing steering mechanism, though.
Worst case (sometimes the best option, sometimes the only option), you strip out all of the control electronics, and then use some other driver circuitry that is easier to control with your microcontroller of choice to control the actuator(s) and drive motor(s).
HazardsMind:
But if you want to add things to the RCs, then yea, its a pain in the butt. But if you just want to mod the rc to work with an Arduino, just for fun or to say that you did it, then it is very easy.
Most toy RC vehicles, once stripped of the outer shell, can be easily modified to add a "deck plate" onto which other things can be attached (sensors and such). This deck can be constructed of plastic, plywood, or other materials as needed (foamcore or coroplast can work well - even cardboard can work).
HazardsMind:
I personally prefer to make my robots by hand, from Legos or an Erector set, just so if there is something I want to change or add to it, I can. This also allows me to be creative with the designs too.
The only problem with Erector/Mecanno is typically the weight issue, being steel, but as long as that is kept in mind, the chassis and other systems can be engineered to work around it. Lego, on the other hand, tends to be very expensive for what you get, but it does lend itself to being a great prototyping platform - provided you are willing to take apart your creations.
HazardsMind:
Right now I am building a hollow wheel motorcycle with Legos. I am finished with the design, and now I just need to figure out the placement of the electronics. I do still need to work out how it will balance itself.
That's a pretty neat chassis - and one that puts lie to my earlier comments; in this case, you couldn't easily make that chassis out of anything else (unless you had access to a good machine shop - or a laser cutter and/or 3D printer) - and you would likely want to make the chassis a "permanent" one. I guess in this particular case, Lego wins!
As far as balancing is concerned, you might want to add the ability for the bike to "put a foot down" - maybe some kind of "training wheels" that can be let down as the bike slows, then raised up (like aircraft landing gear) as the bike speeds up and the gyroscopic action of the wheels take over to keep it balanced. You'll probably also want to add some kind of accelerometer or similar sensor so that your robot can determine how far it is leaning as it turns, among other potential issues related with keeping the bike upright...
Thanks guys,
I'd also considered just buying the motors and the wheels and making my own chassis, but even though i have a RepRap (kit) 3D printer, making the fixings for the motors etc, is always more complex than it first seems
Designing stuff for 3D is often very time consuming, and the max size of any one piece on my printer is a little under 20cm square, which may be a bit too small.
I actually have an old RC car chassis, but is one with steering, and one central motor, which drives all 4 wheels, so modifying it to use separate motors on each wheel would be virtually impossible, and using conventional steering would be a nightmare to program.
BTW
Mecanum wheels (http://en.wikipedia.org/wiki/Mecanum_wheel ) would be ultra cool, and have seen a printable 3D design
but I think I"m now getting a long way from the original brief I set myself, and the cost is rapidly increasing.
So I guess it may be cheap 4 wheeled device from eBay or HobbyKing to start with and look at more complex types further down the line
A simple design that isn’t too complex.
