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Old Jun 25, 2010, 09:24 PM
Gravity always laughs last
cadzilla's Avatar
USA, PA, Milford
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Control a servo with a PC

I know this is being done, I'm looking for a simple solution. My goal is to break in a new gas engine and automate the run in process. I can do other things in the shop while the engine is being run. Ideal would be having more than 1 servo so I can shutdown the ignition from the program.

Overwhelmed by what's available I could use some direction on a solution.

Thanks;
RichK
AKA cadzilla,LowTek,spartaju
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Old Jun 25, 2010, 10:02 PM
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Do a google search for "serial servo control"
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Old Jun 26, 2010, 06:31 AM
Gravity always laughs last
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USA, PA, Milford
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Originally Posted by adamdb View Post
Do a google search for "serial servo control"
WOW!! Why didn't I think of that. Been there done that; could spend anywhere from $15-$1500. That's why I'm here asking the question; looking for someone's experience; knowledge; sort through all that's available.
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Old Jun 26, 2010, 10:03 AM
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I'd go for Arduino. It's an easy-to-use microcontroller that can take care of your servo while interfacing with USB.

I've made some pretty cool R/C applications for scale helicopters using this. You can even interface it with any onboard Rx.

Check this out for your particular need: http://www.arduino.cc/playground/Lea...leServoExample

If you go further with this platform, you will be able to easily add temperature sensors for automatic shutdown when too hot or who knows what you may come up with.
Best of all: there's a big enough open-source community out there for you to get help.

Best of luck,

Rod.
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Old Jun 26, 2010, 10:36 AM
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Originally Posted by rcastro View Post
I'd go for Arduino. It's an easy-to-use microcontroller that can take care of your servo while interfacing with USB.
I've made some pretty cool R/C applications for scale helicopters using this. You can even interface it with any onboard Rx. [snip]

Rod.
Looks pretty good. Basic board is about $30 USD. Looks like C code; are there any free compilers available? Is Ardino Programming Language an add-on library?
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Old Jun 26, 2010, 11:23 AM
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The $30 board seems real good, you could do a lot with it. A real cheap and dirty would be 2 x 555's and a R2R resistor network driven from a parallel port. One 555 runs in re-trigger mode at 50Hz triggering a second 555 for 1 - 2ms pulses, the period is controlled by the 8 bit D2A ladder from the pc port.
Andre
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Old Jun 26, 2010, 11:51 AM
Gravity always laughs last
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Originally Posted by Turbotronic View Post
The $30 board seems real good, you could do a lot with it. A real cheap and dirty would be 2 x 555's and a R2R resistor network driven from a parallel port. One 555 runs in re-trigger mode at 50Hz triggering a second 555 for 1 - 2ms pulses, the period is controlled by the 8 bit D2A ladder from the pc port.
Andre
You lost me after cheap and dirty. I used to know what your talking about but will swear under oath that electrons are how we pick politicians

No ones mentioned Pololu RC Servo Controllers yet [ found them all by myself ]. But I don't understand if it's you download code into it or have interactive control. I don't know if the Arduino requires that too. The goal is automate engine break in not revive dead brain cells.
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Old Jun 26, 2010, 12:11 PM
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Years ago when I was teaching Electronics and Computing to secondary school boys I found the Mini SSC1 and used it successfully to build a robot using six servos. It was a mobile platform with an articulated arm and hand for picking things up. It was controlled using DOS BASIC back then.

I did a quick search and it appears that now there is the Mini SSC2. It's available here: Scott Edwards Electronics

There are many resources available and it appears to be programmable from many different languages.

Cheers,

Eric
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Old Jun 26, 2010, 01:56 PM
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Originally Posted by cadzilla View Post
Looks pretty good. Basic board is about $30 USD. Looks like C code; are there any free compilers available? Is Ardino Programming Language an add-on library?
It is simplified C code. Easy to learn, full of tutorials and code you can download (and not necessarily understand).

The board comes with a FREE and complete development environment (editor+monitor+compiler).

It's an open source hardware and software platform. To compile and program the chip you need nothing else than plugging it in to your USB port, and hit the "play" button.
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Old Jun 26, 2010, 02:03 PM
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just wondering if a soundcard would be able to generate the signal?
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Old Jun 26, 2010, 03:19 PM
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just wondering if a soundcard would be able to generate the signal?
Good point, probably easy to do.
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Old Jun 26, 2010, 04:25 PM
jab
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Quote:
Originally Posted by cmulder View Post
just wondering if a soundcard would be able to generate the signal?
True, but at 44100hz you will only get 44 servo steps.

I second the Arduino approach. Get the Duemilanove version with built in USB to serial converter. The Arduino code to control a servo literally takes less then 10 minutes to write.
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Old Jun 26, 2010, 08:41 PM
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I've used a picaxe to do something similar.

Was a cheaper option for me than building a 556 circuit, and more versatile.
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Old Jun 27, 2010, 04:25 AM
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Originally Posted by cadzilla View Post
WOW!! Why didn't I think of that. Been there done that; could spend anywhere from $15-$1500. That's why I'm here asking the question; looking for someone's experience; knowledge; sort through all that's available.
Google is your best option... if you enter the search string as suggested you'll find lots of options from ready built USB units to DIY projects such as the 8ch SSC here . I've built this unit and it work fine with the free software provided on that site, but if you really want fine control then you will need to spend $40 or more on a decent package like this one and then another 50 for some descent software such as this
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Old Jun 27, 2010, 04:26 AM
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Easiest (probably the cheapest also) way IMO:

Get a Serial Servo Controller from Parallax or Pulolu. Depending on what you need the servo to do, either use the free software provided by Parallax / Pulolu or buy RoboRealm (or use the free, older version that lurks the forums here). Hook it up and you're done. I've used this set up to control a 4 motor (thruster) underwater robot, works like a champ. No need for Arduino, way more processor than you need for this task.
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