go_away

Author Topic: 3Π Robot from pololu.com  (Read 2592 times)

0 Members and 1 Guest are viewing this topic.

Offline izuaTopic starter

  • Supreme Robot
  • *****
  • Posts: 682
  • Helpful? 0
3Π Robot from pololu.com
« on: September 21, 2008, 07:12:32 PM »
Anyone has any experience with the 3PI robot from pololu?
I never got to finish a real robot, due to the lack of dedication/patience/components, or just because i'm not good at mechanical stuff. However, this guy seems nice - a lot of space for electronics experimenting, a nice MCU, and a working hardware platform. The speed seems amazing. Kindof expensive though, for everything it has.

Here's a link. http://www.pololu.com/catalog/product/975
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline JesseWelling

  • Expert Roboticist
  • Supreme Robot
  • *****
  • Posts: 707
  • Helpful? 0
  • Only You Can Build A Robot!
Re: 3Π Robot from pololu.com
« Reply #1 on: September 21, 2008, 11:55:32 PM »
Looks good to me. The only thing I don't like is there is no encoder on the wheels.
Maybe if you want latter you could shoe-horn in two of these? They appear to be the same size...

I don't think it's that pricey. A good plus is it's AVR  ;D We love AVR's around here. IIRC you are a Computer Science guy so GCC and C is nothing new to you, so you should be just fine on the software side, especially with the Polulu Library and the AVRlib. You should have plenty of examples.
« Last Edit: September 22, 2008, 12:02:56 AM by JesseWelling »

Offline izuaTopic starter

  • Supreme Robot
  • *****
  • Posts: 682
  • Helpful? 0
Re: 3Π Robot from pololu.com
« Reply #2 on: September 22, 2008, 11:58:40 AM »
I like this little guy because he's speedy. A stepper with such a reduction would probably kill that speed. Never tried those stepper modules, though.

AVR is a plus, definitely (and no, I have absolutely no problem with them on the software side :D), a lot of roboticists prefer this architecture.
But the position of the chip is quite exposed - under the chassis. A chip with more pins would made me buy this instantly - but with only two user pins, I'm not sure if everything I want can be added.
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline JesseWelling

  • Expert Roboticist
  • Supreme Robot
  • *****
  • Posts: 707
  • Helpful? 0
  • Only You Can Build A Robot!
Re: 3Π Robot from pololu.com
« Reply #3 on: September 22, 2008, 08:00:45 PM »
You could replace some sensors, but if you aren't into soldering it might be a pain :-\

As for the exposed AVR, slap some hot glue on it.

Offline Webbot

  • Expert Roboticist
  • Supreme Robot
  • *****
  • Posts: 2,121
  • Helpful? 108
Re: 3Π Robot from pololu.com
« Reply #4 on: September 23, 2008, 01:57:46 PM »
A chip with more pins would made me buy this instantly - but with only two user pins, I'm not sure if everything I want can be added.
As you've probably noticed there are jumpers that can disable some of the built in stuff - allowing you to claim the I/O for your own use. But yeah - know what you mean!
Webbot Home: http://webbot.org.uk/
WebbotLib online docs: http://webbot.org.uk/WebbotLibDocs
If your in the neighbourhood: http://www.hovinghamspa.co.uk

Offline bens

  • Expert Roboticist
  • Supreme Robot
  • *****
  • Posts: 331
  • Helpful? 3
Re: 3Π Robot from pololu.com
« Reply #5 on: September 24, 2008, 05:18:21 PM »
As Webbot said, you can get a third digital I/O by removing the PC5 jumper.  When the jumper is in place, PC5 controls the IR emitters for the sensors; when the jumper is removed, the IR emitters are just on all the time.  PC5 can also be used as an analog input.  You can get two more analog inputs by removing the ADC6 and ADC7 jumpers.  The ADC6 jumper connects ADC6 to a voltage divider circuit that monitors the battery voltage, and the ADC7 jumper connects ADC7 to the user trimmer potentiometer on the underside of the board.

The two completely free digital I/O lines are PD0 and PD1, which happen to be the UART receive and transmit lines on the ATmega168.  What this means is that you can program the 3pi's microcontroller to function as a "dumb base" that acts in response to received serial commands from another microcontroller (such as a Basic Stamp, Arduino, Orangutan, Axon, etc).  This secondary microcontroller could connect to all of the extra sensors and electronics you want, and it would control the 3pi's motors, buzzer, and LCD through a serial interface with the base.  To help make this possible, we will begin selling expansion decks for the 3pi in a few weeks.  These expansion decks mount just above the wheels using four standoffs.  They provide lots of prototyping space and will give you convenient access to key pads from the lower deck (e.g. the unused or optionally used microcontroller lines PD0, PD1, PC5, ADC6, and ADC7, all of the ISP programming lines, the battery charge port, the power button pads for installing a secondary power button, and LCD lines).  We also plan on providing a program that will turn the 3pi into a serially controlled slave base, but we might not have that ready by the time we start selling the expansion decks.

- Ben

 


Get Your Ad Here