Hobby Servo Question

Sell the servos and use the money to buy used stepper motors as the changes you need to make to the servos for accurate replicable movement will cost more than proper secondhand steppers. You probably need special encoders added. A lack of basic accuracy will kill you later on if you don't do that.....fiddly work.

Servos are very good, if you have the necessary funds and they are bigger industrial types, no doubt in my mind, but model control servos will also have very limited speed and or torque and are small with usually plastic gears.....

Watch out when buying steppers as the best ones (except for some very high end stuff) are Bipolar only and need only a Bipolar driver system which costs more, but gives very good torque - very important.

Some steppers are Unipolar (but they can also be driven Bipolar), and the plus is that Unipolar electronics are slightly cheaper/simpler to make or buy generally, but you do not get as much torque from the same motors as with Bipolar.....

Proper servo control from say a PC costs more than stepper contro due to having feedback., but money can be saved by a self build using fine chips available today from many manufacturers, if you want names and numbers just ask!!

Servos are generally faster.....

Note the stepper motor type on an ebay auction for example and research its parameters and type. The voltages given are seemingly very low, but they are driven using spikes of a far higher voltage to make them quicker and to have good torque. Usually a good steady 24 volts will have most small 6-10 volt motors really humping, but do not overheat them!!!

No feedback needed for steppers (saves on complexity, some high end ones do have it) as long as the motor has enough or more than enough torque for the application.

Motors needing between 1 and 3 amps are usually great for many applications and are easy to find 2nd hand on ebay. I bought 30 x 2 amp motors for slightly over US$20 a few years ago. Only one was defective, but supplied some good spares for the others.....

An old PC with just DOS or Win95 or 98 will do provided it has, or can have a printer port....

USB is also available but due to timing restrains, can be a problem to get running well, stay away from any USB stuff at least in the beginning as the interfaces AFTER the USB port are far more expensive, to handle the timing problems properly, and generally slow down the working of your masterpiece, if they work at all.

A good maker of chips for steppers is Allegro, especially the newer chips, which do not require an external resistor as most of the others do from most companies.....available from ebay usually China or Hong Kong.....for around US$20 each plus post.....

Do join plenty of online CNC Forums for help, tips and assistance as well as cheap/free equipment.

Join Yahoo forums and search out those for CNC.

Search on Google using "DIY CNC", also on YouTube, read watch and learn before spending ANY money, many pitfalls!!!

Start here:-

http://buildyourcnc.com/

CNC does not mean "Command 'n Conquer", but you will get many hits for such games from Google when searching.....sadly!!!

Best of luck.

The servos you have are pwm controlled...the industrial servos are dc bidirectional and usually tied to an optical encoder and servo-amp controlled by a computer. Check out adafruit and Radio Shack, they stock a 14$ hbridge driver w/5v interface that can handle 25w at up to 48v and 2 analog or 1 stepper...the steppers from old 5&1/4 1/2 or full height floppys work great and I used to overdrive Riffa 3770's with a heatsink but at !4$ the adafruit parts are a steal for steppers.