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Electronics => Electronics => Topic started by: videorov on April 21, 2008, 11:47:42 PM

Title: Best way to control servos over wire not radio.
Post by: videorov on April 21, 2008, 11:47:42 PM

I want to control two servos to control a pan and tilt camera. The camera is going to be under
water in a waterproof housing. I want to be able to control the servos by the copper wire going
down to it at 100ft down.
What is the best way for me to control these servos over the wire?
I would like to pan up to 180 degrees left and right. Maybe a stepper motor would be better?
What is the best way to control a stepper motor over the wire 100ft long?

I would like to stay using 12volts for power also on the boat.

Hope you can help me.

Title: Re: Best way to control servos over wire not radio.
Post by: airman00 on April 22, 2008, 05:12:10 AM

I would buy the Logitech Orbit USB camera ( it tilts and pans)
Then calculate the voltage drop your 100 ft. of wire has.Then power the USB camera separately from the USB port ( its own battery) and the serial data from the USB camera can be connected to your laptop's USB port.

Or you could just connect your servos to a serial controller and control that serial controller on one wire.

Title: Re: Best way to control servos over wire not radio.
Post by: videorov on April 22, 2008, 07:31:28 PM

I don't think I want to mess with batteries for running the camera to boost the power of the cable.
Ive decided I don't really need the tilt. I just need the panning 180 to the left and right. I was looking at
stepper motor sites and looks like there are controllers that I could use to even set up a auto panning
sequence that would run by itself to keep looking around by its self. I would also have manual control
to pan left and right.
Any ideas for controlling stepper motors to pan my small board camera?
Have you played with stepper motors airman00?

Title: Re: Best way to control servos over wire not radio.
Post by: airman00 on April 22, 2008, 07:36:24 PM

yep i have played with them

just get a stepper motor driver from online

the problems with your idea is that the camera video signal and the signal going to the steppers gets weaker after 100 feet of wire. You need to take that into account and  use buffers ,  amplification ,etc.

Title: Re: Best way to control servos over wire not radio.
Post by: JesseWelling on April 22, 2008, 10:07:27 PM

Tractors use Controler Area Network (http://en.wikipedia.org/wiki/Controller_Area_Network) or CAN.

From the Wiki:

Quote

Bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Decreasing the bit rate allows longer network distances (e.g. 125 kbit/s at 500 m).

SparkFun has a nice dev board (http://www.sparkfun.com/commerce/product_info.php?products_id=8279) that we tinker around with at work.
Keep in mind that this is probably the most robust and expandable method but not the easiest to implement.

EDIT: Here are some stepper motors you might be interested in.
Really Small Ones (http://www.phenostream.com/products/gsm.aspx)
<a href="http://www.sparkfun.com/commerce/product_info.php?products_id=8420>Medium Size from Spark Fun[/url] (they have a 'EasyDriver' as well.)
RobotShop (http://www.robotshop.ca/home/products/robot-parts/motors/stepper-motors/index.html) has a wide range of steppers as well.

Another option might be to just wire up the stepper motor and a Stepper Controller and control everything from a long wire on the surface... of course this might have a problem with signal drop along the wire as well...

Title: Re: Best way to control servos over wire not radio.
Post by: Admin on April 26, 2008, 06:43:54 PM

please avoid double posting:
http://www.societyofrobots.com/robotforum/index.php?topic=3935.msg30512#msg30512