what is difference between ac & dc motors?

[dseeber]

I know this may sound stupid, but I'm a new user and I'm doing the 50$ robot tutorial. When i looked online for the HS-311 servo they were all
really expensive, so i want to buy two ordinary motors and use them instead. thing is, does it matter if its AC or DC and once i know how do i wire them up to the circuit board?

[TrickyNekro]

Well..... Kinda huge if you ask me.... although some AC motors are reported to work with DC.... I haven't confirmed that myself.....
You need DC motors.... But.... IF you get DC motor you also need something to "drive" them aka to use them with the microcontroller...
Cause the microcontroller can not handle the current a motor requires to work... and thus will burn itself....

So... You need an motordriver..... The most common is a H-bridge that allows bidirectional control.... Check the site itself.... Should you see
a lot of info and schematics..... especially on userpages



Regards,
Lefteris

[dseeber]

when you talked about "checking the site" did you mean this site? and how do i get to userpages??

[TrickyNekro]

Of course I mean this site!!! It pretty much has everything for a beginner and intermediate user!!!
Hit the big label which says "Society of Robots"
And take a look around member pages and tutorial.... I hope you know how to surf the net....

[dseeber]

thank you very much =)

[Metal Slug 2]

Just google the difference between DC and AC motors:

http://ecmweb.com/mag/electric_differentiating_dc_ac/

In order to use any DC motors on your robot you will need a motor driver, as stated above by TrickyNekro.

You can find some motor drivers here:  http://www.solarbotics.com/

Perhaps this motor driver kit may work for you:  http://www.solarbotics.com/cad/products/k_cmd/

To view "userpages", what TrickyNekro meant was the Member tutorials (or "member pages" - the link is found on the left sidebar of the main page, under "misc"), which may be found here:  http://www.societyofrobots.com/member_tutorials/

you can also find a whole bunch of help on previous forum topics relating to your troubles, such as these:  http://www.societyofrobots.com/robotforum/index.php?topic=3244.0 , http://www.societyofrobots.com/robotforum/index.php?topic=6868.0 , and http://www.societyofrobots.com/robotforum/index.php?topic=3669.0  (there are many more)

Also, if you want to make your own H-bridge (another device used to control motors), check out this schematic made by Admin : http://www.societyofrobots.com/schematics_h-bridgedes.shtml

[Webbot]

Make your own DC motor controller:- http://www.societyofrobots.com/member_tutorials/node/159

[paulstreats]

Motors do look cheaper from the unexperienced point of view but...

 As mentioned above you will need to buy additional circuitry to use a motor. motor controller / hbridge (for each motor).

 Gears. A motor normally wont have enough torque to pull a robot but they spin at 10,000+ rpm (think about how fast 10,000 revolutions per minute is... Ive got one that spins at 29,000 rpm that im gonna use to mod an r/c helicopter with). You have to gear down the speed and gain torque in the process, reducing speed with gears gains pulling power. So you have to include a gearbox for each motor. Or buy motors with gearheads attached(probably more expensive than a servo).

Youll soon see that servo's are generally cheaper (a servo is basically a device that includes a motor, a gearbox and a h-bridge built in - with its own feedback system and control system too).

The difference is that with servo's you are limited to the speed and torque of the servo. Building your own drive system you can specify your own speeds and torques to suit your requirements (but at a cost)