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Barbie Web Rover


aloishis89
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Me and 2 of my friends have been working on a large web rover based off of a kids PowerWheels car. We aren't completely done, but it is drivable from anywhere in the world right now. It still has a couple bugs to get worked out. I had wanted to build a web rover before, but it was always too much money. The major design feature of this rover is as low cost as possible. Hopefully this will help other people who want to do the same. Because of the scale, we had to use different electronics and code which is all documented on the site I built for it. You can find that below. I would appreciate any feedback on the project and any suggestions for fixing the last couple bugs or ideas for a better UI for driving it (right now its just PHP buttons like the one Darren did). Sorry for the crappy website, but I'm still working on my web designing.

site: http://www.prism.gatech.edu/~hscott7/rover/

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The main problem right now is torque.

I remember seeing somewhere the a person tookt he motor out of a hand drill to put in an RC car. I imagine the torque of a strong hand drill should be more than powerfull enough to push this around. Maybe use two, one for each side, front and rear, so you then have 4-wheel drive, so its more stable and can go off road a bit more. Not sure how you would mount or include it in the project, but just an idea I am throwing out there. You would need to create some sort of gear mechanism to interface with the drill motor to the wheels though.

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You're right, I had thought about doing that but we did some more tests and it looks like the motors we have can put out enough torque, but they are being limited on the amount that they can draw. We bought motor controllers that, at the time, we thought could handle our maximum current draw but they ended up not being enough. Buying higher rated ones is too expensive, so we had to use resistors to limit that. Right now we have 2 ohms of resistance, but we are going to try to bring that down to 1/3 or 1/2 an ohm and that should help some. Really, with the motor controllers we have, there will be a limit to how much current we can squeeze through (unless we spend another $100-120 for new controllers) and we are trying to get as close to that limit as possible.

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Is the power you are reducing going through the arduino and then to the wheels/motors?

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What about the traction? You could take a bike tire and strip it down into strips to get better traction. But then we got traction vs torque.

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(unless we spend another $100-120 for new controllers)

you should be able to find speed controllers that can handle 10amps continuous shouldn't cost you that much more like 30. I could build you two controllers that could handle 9amp spikes for $10. You don't need a victor or jaguar speed control for a little banebot motor :P if you were to switch to the fisherprice motor / gear box you could probably have more control over your torque problems, and they were originally designed for these little kid cars.

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@thedude: Treads will help for driving off road, but right now I am almost positive that it is the current draw that is causing the problem. We connected the motors directly to the battery and it had plenty of torque.

@Dead_Already: We were actually pretty curious as to how our motor controller worked. I would be interested in building my own if I could. I'm not sure what our current draw is exactly, but I think a 15 amp peak should be enough (its a 3-12v motor running at 18v). Is building my own worth attempting?

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What kind of gear box are you using? I think 15amp peak is way over kill, but i will look into it and get back to you. I always like to build everything myself, so you might want to look into making your own but it would involve some programming.

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We are using the stock gearbox. It was designed to be used for ~50 pound kids, so we figured it would suffice. Yeah, let me know about making my own controllers. You mentioned that it would involve programming and if by that you meant writing code, then thats no problem, but if you meant buying a chip programmer, then I may need to wait until I get back at college to use one.

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  • 3 weeks later...

A couple of tips:

With plastic tires traction is bad, so I would recommend either getting rubber tires or painting the tires with a liquid rubber for more traction.

If you have a cell with a usb plug, I would recommend getting internet for your phone and using it as a modem. That would give you a much longer range than the wireless modem you are currently using. I don't think it would cost too much. On my cell plan it is only $10 extra a month for internet.

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Does it have to be proportional or not?

If it doesn't, go for something like an H-bridge, if I remember correctly, there is a way to make a proportional speed controller using an lm-386 opamp or an octal buffer chip, I was reading up about it from a book in the public library. I'll see if I can find it again.

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After considering building our own, we decided to buy one. Its a little pricey at $125, but its 2 channel, and has a continuous current rating of 25 amps with a 50 amp peak. This is WAY more than we are letting it draw right now, so the rover should go much faster and have much more torque. The new motor controller is a Sabertooth 2x25. We decided to buy one because we knew that it would work off the bat, we could get it soon, and it has features like the ability to recharge the battery when the motors slow down or go in reverse.

The parts should be coming in next week, and once we get them hooked up and working, I will update the website with pictures and video. I have also been through a couple more version of the code, so I will get that up once we test it.

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  • 4 weeks later...

I agree with Stacked. You should teather your cell phone to the laptop so your using the cell network and not wifi via the linksys. This way finding hotspots / loosing connectivity is not a big a problem.

Also you should maybe build some armor on top of all the equipment so someone has a harder time snatching your laptop if you drive it farther down the street.

I'm excited to see the new build!

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  • 4 weeks later...

@VoodooTorture:

We would like to be able to tether a cell phone for internet, but we don't really have the budget for that. Me and 2 of my friends are the ones working on it, and we all go to separate colleges during the school year, so the only time we have to work on it is during breaks or over summer. So paying for an unlimited data plan over an entire year would be kind of wasteful at this point. As for protecting the laptop, some sort of armor would be a good idea. We have speakers on the rover, so we joked that if someone got too curious, we could drive in the bushes and play dog barking audio and scare them off :D. I updated the site with some new writeups for the latest version, but I won't have pictures or video for another couple weeks.

@stacked:

Good to know, we'll try it.

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I found something that would add that will increase your range immensely. (3-5 kM) And incredibly cheap too.

It is known as wifry, wokfi, etc. Essentially you use asian cookware to magnify the wifi signal, similar to a satellite dish.

Info here:

http://www.usbwifi.orconhosting.net.nz/

http://www.instructables.com/id/%22Poorman...-cookware-refl/

http://en.wikipedia.org/wiki/WokFi

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  • 3 weeks later...
I found something that would add that will increase your range immensely. (3-5 kM) And incredibly cheap too.

It is known as wifry, wokfi, etc. Essentially you use asian cookware to magnify the wifi signal, similar to a satellite dish.

Info here:

http://www.usbwifi.orconhosting.net.nz/

http://www.instructables.com/id/%22Poorman...-cookware-refl/

http://en.wikipedia.org/wiki/WokFi

Wow, that's a really good idea. I had thought about making a cantenna, but I didn't think of using something like a wok instead. We will definitely look into that, there's a pretty high chance we'll make one. I am on a BattleBots team, and I also happen to know that a big steel wok makes a great housing for a robot (google for Blendo) and is way cheaper than buying a big steel hemisphere. Asian cookware can be very versatile!

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This is what I use.. has anyone tried putting tin around it like this, does it really double the signal? I currently have a 8dbi antenna on it instead of the factory

alfawind.jpg

that wok antenna looks pretty awesome too, i would like to get the most range that I can get for cheap

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