Let's Make Robots!

Building Stair Climbing Robot and have power question.

I am building a stair climbing robot for a class that will carry a basket full of rubber stamps to the top of a staircase.  My robot will be loosely based off of this robot --->http://letsmakerobots.com/node/8355.  I am planning on using an Arduino Duemilanove for the microcontroller.  I am planning on using 5 dc motors to power the four wheels on the ground, and 1 continuously rotating servo to power a wheel rotating at the front of the robot which comes into contact with the stair first and projects the device upwards.  My problem is wondering how to power 4 motors and a servo continuously? I also need to have the front pair of motors and the back pair of motors to rotate in opposite directions initially and then stop and rotate in the same direction.  

What is the best way to go about this?

Sorry I am very new to robotics.

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If you have a choice then start by buying a board like GuiBot's Motoruino or my Magician controller. These are Arduino compatible boards with motor controllers built in as well as servo connectors.

If your motors need more current then try a Romeo board which can drive up to 2A per motor.

Using one of these boards means you only have to worry about building the robot body and programming it. The electronics is already done for you.

(As to how to make the motors rotate in different or the same directions, while it is possible to make the motors switch direction using individual transistors and logic gates, it will be better if you use a micro-controller chip.)

You mentioned using an Arduino, but if you are new to robotics, my advice would be trying a very simple controller like a PICAXE chip. They are only a few dollars (US), and in general are easier to understand and program. The simplest picaxe chips (the 8 pin ones) will not be able to run 4 motors and a servo due to not enough individual pins.  Personally I would probably use nothing less than the 18M2, which sells for £2 in the UK (www.picaxe.com) or $5.95 US (www.solarbotics.com). That has two pins for battery and ground and 16 in/out pins. 8 x "B" pins and 8 x "C" pins. Using 2 pins each for the motor controls and one for the servo leaves 7 pins for other things like leds or sensor inputs. My personal favorite is the 28X2 chip (AXE010X2 is the 28X2 new style and sells for $8.50 US), but there is a variety to chose from. Also, just as with the Arduino, you will need a connecting cable so you can program the chips from your PC or laptop.

If you already know how to program in languages like C++, then the Arduino will be fine, but if you do not, I would advise the picaxe. It has its own programming language that is fairly easy to learn. The programming (and how to connect the hardware) is available as free, downloadable manuals.

---(and No, I don't have anything to do with the company. I just like them and use them myself.)