Author Topic: 2 rotation servo?  (Read 703 times)

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Offline mstachoTopic starter

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2 rotation servo?
« on: September 17, 2011, 12:33:19 PM »
Hi all,

I'm working on a project where the steering is done via a proprietary sensor that we can't change (sadly...because it sucks :-P ).  It's a mobile robot.  In order to turn the wheels all the way to the left, you have to rotate the shaft of the sensor by 360 degrees from the neutral position.  similarly for all the way to the right.  So if we do mate a servo to the sensor, it would have to be able to turn 360 degrees in either direction, not just the standard 180.

Although we could do it with gearing, we'd rather not, since it's remarkably hard to find good quality gears that can be made in small quantities for cheap.  So, does anyone know of a servo that takes a standard servo input PWM command but rotates 360 degrees in either direction?

We did manage to find a 3.5 rotation servo, and it's our solid plan B, but I'd rather just take a ready-made solution that does what we want.

MIKE
Current project: tactile sensing systems for multifingered robot hands

Offline joe61

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Re: 2 rotation servo?
« Reply #1 on: September 17, 2011, 03:24:34 PM »
I haven't used it, but Pololu has this.

Perhaps a stepper motor?

Joe

Offline ChrisW

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Re: 2 rotation servo?
« Reply #2 on: September 18, 2011, 12:53:12 AM »
can anything be done to adjust the linkages to fit the standard servo?

sorry just can't picture you scenario in my head but i've also been up for 22+ hours so head is a little sketchy...

Offline mstachoTopic starter

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Re: 2 rotation servo?
« Reply #3 on: September 18, 2011, 06:35:17 AM »
Not really...the sensor is something I've never seen before.  At first glance I thought it was just a DC motor, and in fact it looks almost identical -- a cylinder with a shaft attached.  But there are some oddities.  First, the sensor makes a clicking noise at about 15Hz.  Then, the sensor's output, when viewed on an oscilloscope, doesn't really look like anything, so I'm not even sure what it's doing.

Finally, the sensor, for some reason, is capable of rotating around and around, and the steering motor itself must have some kind of limits on it, because the wheel at the back that actually rotates only goes between certain limits.

I'd be up for just recreating the sensor's output, but I'm at a loss as to what it even is.  :-P Oh and to complicate matters, the robot is old, so the sensor's marking have all worn off.

Haha BUT! if anyone knows what this thing is that I'm talking about, let me know!

MIKE
Current project: tactile sensing systems for multifingered robot hands

 


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