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geared servos and stepper motors and plain servos


 I've just joined couple minutes ago, searching the net came accross the drummer bot and then this site. First, greetings to all the beautiful minds here :)


ok. here goes:

1. what is the difference between a geared servo, stepper motor and a plain servo like ones found in simple toys or cooling fans.

2. Can anybody recommend a book on electronics or robotics generally that will get the unitiated started?


I used to have an nxt kit, which is now lost, which I believe is the best toy ever but not as flexible when you have some wild ideas for a project. So any ideas and starters are much appreciated.





and another thing, how do you control position. how would it be possible get feedback on the position of the servos at a given time?

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A good all purpose electronics book

Practical Electronics for Inventors 9780071452816

I'd recommend:

Absolute Beginner's Guide to Building Robots (0789729717)

Programming Robot Controllers (0071408517)

Building Robot Drive Trains (0071408509)

Those are ISBNs for UK editions you may get local editions cheaper.


A servo is a motor that has a feedback to tell the processor what position it's in. That is a broad term as different feedback mechanisms can be used. The servos commonly used on this site are RC servos that use a pot for feedback. I'm not sure there is a difference between "plain" servo and "geared servo" as almost all servos have a gearbox.

A stepper motoris a specially designed motor. When power is pulsed in a certain pattern through it's winding the motor "steps" by a precise amount. A common stepper motor usually has about 48 steps per revolution allowing the shaft to turn in increments of 7.5 degrees but industrial steppers cand have 200 or more. This ability to move by a precise amount can eliminate the need for a feedback mechanism but a "home" switch is usually a good idea as the processor does not know what position the motor is in when it is first turned on.

There are some books called "The robot builders bonanza" which have good basic information for beginners covering everything from power supplies to designing and building robot arms.

The second edition shown in the link also covers Lego Mindstorms which my 1st edition doesn't.