Author Topic: A bit of help in designing  (Read 561 times)

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Offline SushiKittenTopic starter

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A bit of help in designing
« on: April 09, 2013, 08:16:33 AM »
Hello!

I've been playing around with robots the past few months. My work term job this semester involved working with robots like the Pololu 3pi, Thymio II, and with different applications of the Arduino, such as building a small two wheeled robot. I've ended up with a bit of an interest in robotics and I want to try stuff on my own. My big goal is to create a biped robot, similar to the Bioloid, but slightly simpler and cheaper since tbh I feel like I can make something similar without paying an arm and leg for their design and software.

I was considering slowly getting each piece I need by making smaller robots, deconstructing them and building up to my biped design. However, as a student, I cannot afford the $40 servos that the Bioloid uses. Are there any cheaper alternatives?

And as for designing a biped robot, I would need a servo for each joint that I want to move, correct? Also, are there any larger microcontroller boards that you would recommend?

And lastly, for someone just starting out in DIY robotics, what would you suggest is necessary to have in your arsenal of equipment?

Offline newInRobotics

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Re: A bit of help in designing
« Reply #1 on: April 09, 2013, 08:39:55 AM »
And as for designing a biped robot, I would need a servo for each joint that I want to move, correct?
Yes.

Also, are there any larger microcontroller boards that you would recommend?
You have to define Your requirements first in order to know what microcontroller to get. Things like: how many sensors (analog or digital) You are going to use, how many general IO pins You require, are You going to do some serious number crunching requiring a lot of cycles, or maybe requiring high precision, do You require ability to communicate with PC, or another uCs, etc etc., have to be answered before getting microcontroller , because there is no ONE perfect chip to fit all applications. However, as You are a beginner, something like Arduino or Axon will do nicely for some time, or if You fancy to learn building MCU and how all of it works, get prototyping board, pack of mixed resistors, caps and LEDs and something from ATMega series (my choice was ATMega48 as it was cheapest ATMega uC on eBay at the time).

And lastly, for someone just starting out in DIY robotics, what would you suggest is necessary to have in your arsenal of equipment?
Soldering iron, prototyping board, multimeter and jumper wires (and some wires in general, they can be scavenged from dead appliances and PCs) are A MUST in my opinion. If You can afford oscilloscope and lab power supply, then they are great tools as well and can save You loads of development time.
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Offline jwatte

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Re: A bit of help in designing
« Reply #2 on: April 09, 2013, 03:37:32 PM »
Multimeter: Definitely! Also, some kind of power supply with wire or banana ends. Get a 9V / 1.5A supply from some piece of electronics you're no longer using, and cut off the plug, perhaps; it's a good start. For stronger motors, you'll want more power, though.

I'd get a logic analyzer ahead of an oscilloscope. Something like the Saleae Logic has been great when debugging robot control systems for me.
If you do more analog things, an oscope is of course crucial! But, one thing at a time.

Another thing I'd get early is an Atmega serial programmer, like the USBTinyISP. This lets you get cheap Atmega and Attiny chips and program them without needing the extra overhead of the Arduino boards.

Regarding servos: It is possible to build bipeds with hobby servos. It won't be as robust as using robot servos, but it's possible. About the cheapest I would go would be the Solar Servo brand from HobbyPartz; $17.50 for a Solar D772, which probably has enough torque for a walking biped. (Smaller servos like the Hitec 332 or whatever don't.) http://www.hobbypartz.com/33p-solarservo-d772.html

Also, walking robots use a lot of power, no matter what the servo. For hobby servos, use 2S (7.4V) LiPo with at least 1500 mAh capacity. For robot servos, use 3S (11.1V) with at least 2000 mAh.

Offline SushiKittenTopic starter

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Re: A bit of help in designing
« Reply #3 on: April 09, 2013, 03:53:51 PM »
Thank you very much, guys! I'll definitely save up for the items you guys mentioned. For now I have access to most to all of those things as an engineering student, but I'd like to have a set of my own. Definitely will start with a handheld multimeter.

I'll consider trying to build my own MCU. I am doing a course in the summer on microprocessors and microcontrollers, and perhaps working on my own MCU might help me with said course.

And thank you for the help on the servos. I was going to try a $15 one on SparkFun but I didn't really want to buy it without knowing if it would work.

 


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