### Author Topic: "These servo's only have about 60 - 90 degrees of rotation"  (Read 3575 times)

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#### Vince

• Jr. Member
• Posts: 18
##### "These servo's only have about 60 - 90 degrees of rotation"
« on: January 23, 2009, 07:19:43 PM »
"These servo's only have about 60 - 90 degrees of rotation"
-Guy at Hobby City

I went to Hobby city, and the guy there said that servo's don't rotate 360 degrees like a motor or something. He was saying that they would operate things such as the wing flaps on an airplane.

Now I'm really confused - everyone refferes to these auto motor things as servos, but obviously there is some sort of differece

I live in New Zealand, and I have no idea how this is possible, except maybe a difference from American terms to NZ terms. But I could sware the servo's there looked like servo's.

#### izua

• Supreme Robot
• Posts: 682
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #1 on: January 23, 2009, 07:22:30 PM »
In basic terms, a motor converts electricity to motion.
A RC servo sucks up electricity, and depending on an additional signal will move to a position. An RC servo can't rotate 360. It will only do 60, 90 sometimes even 180 degrees.

A servo is built for a different purpose than a motor.
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#### Vince

• Jr. Member
• Posts: 18
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #2 on: January 23, 2009, 07:25:03 PM »
so everytime Admin says 'servo' in his RC video video he really meant motor?

#### kd5kfl

• Full Member
• Posts: 72
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #3 on: January 23, 2009, 07:26:54 PM »
To make servo a motor, you cut off the stops and hard-wire the pot.

http://www.societyofrobots.com/actuators_modifyservo.shtml

#### HDL_CinC_Dragon

• Supreme Robot
• Posts: 1,261
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #4 on: January 23, 2009, 07:31:49 PM »
A servo requires a specific signal to be sent to it for it to move. Depending on the signal, it will move to a certain angle. An unmodified servo usually cannot move more than 360°. Most servos can only move 90° maximum or 180° maximum. Servos require a power connection, a ground connection, and a signal connection.

A motor has no function other than off an on. When 'on', it will continue to spin until the power is cut off. For the purposes of the \$50 robot, a servo was modified so that it could spin continuously just like a motor. The reason Admin did this is because to drive a regular motor you need a motor driver which is a more complex circuit and also adds bulk and money to the project.
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#### Vince

• Jr. Member
• Posts: 18
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #5 on: January 23, 2009, 07:35:20 PM »

You Guys Rule!!

Obviously the guy in the shop doesn't know much about robotics, but I don't blame him, the shops specialised for planes and models!!

Thanks so much

It all makes sense now

#### HDL_CinC_Dragon

• Supreme Robot
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##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #6 on: January 23, 2009, 07:38:06 PM »
Well the guy was technically 100% correct. Im sure he doesnt think anyone would need to modify a servo to rotate continuously and he was also right that they are used to adjust flaps and rudders and all that jazz.

-EDIT-
Plus he cant suggest modifying the servo because then he is liable if the servo gets broken beyond usability and repair.
« Last Edit: January 23, 2009, 07:39:33 PM by HDL_CinC_Dragon »
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#### Vince

• Jr. Member
• Posts: 18
##### Re: "These servo's only have about 60 - 90 degrees of rotation"
« Reply #7 on: January 23, 2009, 07:46:35 PM »
true
true,

But it was obvious I needed continous ones.

In the end he ended up suggesting speed controllers or something, which I've also read about so he was right about that too.

Also asked him 'bout recivers, he said they generally come wth controllers and proceeded to tell us we'd probably have to pay \$750 NZD for it  ... I don't think so.

You guys still rock though

I'm just buildig a robot cause I'm bored, and I used to be a part of the Kristin (a school) F.I.R.S.T Robotics team, hoping to learn alot about it. Unfortunately our sponsors pulled out because of the recession

so we couldn't compete

-EDIT- Oh and because when I'm older I want to be fluent with robotics (but not do it in university). It sounds like a very fun thing if you're good at it, and very userfull skills too
« Last Edit: January 23, 2009, 07:48:25 PM by Vince »