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PC to servo interface

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Old 09-24-2003, 07:33 AM
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Marek G
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Default PC to servo interface

Hi,
I need to controll servos through serial port in my PC.
I know it is usually done by interface board so I am looking for board design capable of controlling up to 8 servos with 1024 steps fo each. I will be using Hitec digital servos.

thanks in advance, Marek
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Old 09-24-2003, 08:40 AM
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Default RE: PC to servo interface

Take a look here at http://www.robotzone.com/cgi-bin/sho...ion&key=SC8450

Thanks!
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Old 09-24-2003, 08:51 AM
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Marek G
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Default RE: PC to servo interface

Thanks Tech-RCU,
but I am looking for servo controller capable of delivering 1024 steps for each servo ( this one is 256 only ), the second thing is ( I am not sure here ) "proprietary method of stepping each servo from a start point to an end point before moving on to the next servo". ( In fast plane it could result in crush )

Thanks, Marek
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Old 09-24-2003, 06:04 PM
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Default RE: PC to servo interface

Marek, what do you need 1024 resolution for?
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Old 09-24-2003, 06:15 PM
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Default RE: PC to servo interface

I need to controll servos through serial port in my PC.
A nice roundup of servo controllers was published in the Feb 2003 issue of Nuts and Volts Magazine. Reprints are available: http://www.nutsvolts.com/toc_Pages/feb03toc.htm#

I am looking for servo controller capable of delivering 1024 steps for each servo ( this one is 256 only )
Have you tried a 256 step controller? I think you will be surprised! Frankly, 256 steps over the servo's 120-140 degrees of travel is decent enough for most model R/C applications.

"proprietary method of stepping each servo from a start point to an end point before moving on to the next servo". ( In fast plane it could result in crush )
That is basically the way a PPM R/C system works, so it should be good enough for the servo controller. Each servo is controlled one at a time, in sequence, at the frame rate of the transmitter. If the controller's update rate is fast enough then this is not an issue. If you are like many UAV designers, the positioning update rate is limited more by the PC/embedded control software latency than by the servos or servo controller.
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Old 09-25-2003, 02:06 AM
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Default RE: PC to servo interface

Tanks fo help,
I think I found what I need: www.rotomotion.com 6DOF (6 degrees of freedom and servo contrller ) and the price is acceptable.

I foud something even better: www.micropilot.com MP2028g - but the price tag is huge.


About servo controller resolution, digital servos has 1024 steps so I would like to use that possibility ( I read on this forum that you need this extra resolution for a smooth flight ).

Tanks again, Marek
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Old 09-26-2003, 12:09 AM
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Default RE: PC to servo interface

Higher resolution doesn't really give you that much more smoothness to flight unless you're doing high precision pattern flying. There's just no need for it in practical applications. The cheaper product from Robot Zone in this case would probably be a smarter buy.
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Old 09-26-2003, 06:02 PM
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Default RE: PC to servo interface

here's another interface that you might want to take a look at. It's inexpensive and fast. I know that there is going to be another one out in a month or so, but it will be more expensive, but will be faster and offer more features.

http://www.rc-electronics.co.uk/pcbuddy.htm
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Old 09-27-2003, 04:09 PM
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Default RE: PC to servo interface

That's a serial port to buddy box, what he was talking about was direct servo control.
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Old 09-27-2003, 05:57 PM
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Default RE: PC to servo interface

Sorry about that. I grabed the wrong link Here are a few that I have found

http://www.pololu.com/products/pololu/0290/
http://www.pontech.com/products/sv200/index.htm
http://www.seetron.com/ssc.htm
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Old 09-28-2003, 12:30 AM
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Default RE: PC to servo interface

I have the SSC from Scot Edward Electronics (SEETRON.COM). Works pretty good. I only wish it had at least 8ch.
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Old 09-28-2003, 12:47 AM
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Default RE: PC to servo interface

If the specs on the Pololu one are correct it has a resolution higher than PCM can generate. Good price too. I would however get those specs in more authorative writing before basing a project off of it because it looks like a standard Pic unit.
The Pontech one is your standard pic unit, 4us resolution which is only 250 positions. Same with the SeeTron one. The SeeTron one actually goes up to 8us <bleck>
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