Author Topic: Confused about Cont. Rotation Servos!  (Read 1833 times)

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Offline reefatTopic starter

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Confused about Cont. Rotation Servos!
« on: August 31, 2008, 04:54:29 AM »
Hi,
I am building a Differential Drive based Small Robot. I need to buy 2 Continuous Rotation servos and found two:
    Surplus Hitec HS-5475HB
    Hitec HSR-1425 CR

The only difference I found is, HS-5475HB (61.1 oz-in~76.4 oz-in) has better torque than HSR-1425 CR (38.8 oz-in~42 oz-in). Do you find any other advantage/disadvantage of any of these two servos. Any advice which one should I buy?

Besides, I am little confused about the Cont. Rot. Servos. Are those internal circuits removed from them to make them Cont. Rot.? If so, then do I need any Motor/Servo Driver (like H-Bridge) to drive the servo? Look at  HS-5475HB, it says, "This servo contains no control electronics and no feedback potentiometer." So without the internal circuit, how the servo runs?

« Last Edit: August 31, 2008, 05:10:31 AM by reefat »

Offline Ro-Bot-X

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Re: Confused about Cont. Rotation Servos!
« Reply #1 on: August 31, 2008, 06:45:14 AM »
A servo with the electronics removed is just a DC motor with a gearbox. You need an H-bridge circuit to drive it from your microcontroller.

This is the case for the HS-5475HB servo from Pololu. This servo has karbonite gears and more torque and a little more speed (54 RPM compared to the other servo's 52 RPM at 6V). You still need to clip the limitation nub from the spline gear. I am not sure if I shoud recommend this servo or not, since it does not have enough speed for a fast robot but it has a little more strenght than a regular servo. But you can use the empty space inside to add an encoder.

The HSR-1425 CR servo has the electronics inside, it is allready modified for continuous rotation, the electronics are modified to acheave fully proportional speed (verry good!). This is perfect for a small robot, based on the $50 robot design and code. You don't need to do any modifications on this one.
Check out the uBotino robot controller!

Offline reefatTopic starter

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Re: Confused about Cont. Rotation Servos!
« Reply #2 on: August 31, 2008, 07:20:17 AM »
@Ro-Bot-X . Thanks a lot for this advice. I am going to order 2 of those HSR-1425 CR servos.

Offline Admin

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Re: Confused about Cont. Rotation Servos!
« Reply #3 on: September 01, 2008, 04:30:10 PM »

 


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