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ROV Builder
06-16-2005, 11:48 PM
I am building an underwater ROV and want to use a single fiber optic cable to interface between a topside controller and the onboard Basic Stamp which will control the thrusters.· I don't have much experience with the stamp yet but have a BOE-Bot on order to learn from.· I know this can be controlled through the use of a universal remote so I figure·using similar methods with fiber should work.· Will I need a Basic Stamp topside to convert the controller (probably a PC game controller·or joystick) to a digital signal an·LED·can transmit?

I can't seem to find much information on doing this yet.

I would also be interested in passing video signals through fiber but that is another matter.

Chris

Bruce Bates
06-17-2005, 03:46 AM
Chris -

To the extent that I can. I'll be glad to try and help you do some sourcing for the fiberoptic cable(s) you're looking to employ.

Do you have a particular specification for the fiberoptic cable you want?

What maximum depth are you hoping to achieve?

Will the fiberoptic cable be protected by an outer sheath that you will provide? If so, what is the usable inside diameter of that outer sheath?

How much cable do you expect that you'll need? Are you at all reluctant to use certified surplus fiberoptic cable to keep the cost down?

I presume you'll need all the appropriate fittings as well? Do you have appropriate termination tools, or will you be needing them as well?

Are there any life-safety issues here, that we should know about now?

I trust you realize this won't be cheap, nor will it be nearly as easy or quick as using copper or other similar materials as a signal conductor!

Regards,

Bruce Bates

ROV Builder
06-17-2005, 04:34 AM
I have found surplus fiberoptic cable from MECI
http://www.meci.com/Catalog/Category/bb8cd1aa-b17d-49c9-af93-8045acd2a5a0
I was planning on buying a 100' cable. That should be plenty long for now and keeping the ROV sealed under that pressure is enough of a challenge.

The ROV I have already built uses Relay control with no electronics. My goal is to make the tether thinner and lighter by replacing all the control wires with fiber and add flexibility with the basic stamp. I plan to use H-bridges I will make myself that will interface with the stamp.

I have no specific tools for termination. The cables above have connectors but I don't know which will work for the available optical components that I might use. I may have to reterminate an end to thread the cable through the tether sheath. I may use an outdoor extension cord and remove one wire if possible and replace that with the fiber or thread the wires and fiber through floating rope.

Would I possibly be better off using a single conductor signal cable? I need to be able to expand my capabilities as I add sensors and more things to control. Splicing more cables into the tether is not really an option once it is built.

The main goal is to make the tether as thin a possible. I was planning on using 2 conductors to power the ROV, the fiber cable and one other small cable for video unless that could be replaced with fiber also. Expense is also a concern.

The ROV is unmanned so no safety issues there. It will be operating in the seawater of Puget Sound.

Will these possibly work?

Stock#: 28016 Category: Accessories-Communication
IR Buddy Pair
Price: $39.00

Thanks for the help!

Bruce Bates
06-17-2005, 04:43 AM
Chris -

I'll take a look at the MECI cable and let you know.

You missed the question on maximum depth?

There MAY be a way to use re-enterable heat shrink or cold shrink wrap for the outer jacket. Any sort of extension cord won't last long at all, especially in salt or brackish water.

Regards,

Bruce

ROV Builder
06-17-2005, 06:03 AM
The depthe would be 100' or less due to the tether limitation. Probably more like 75' or so.

Bruce Bates
06-19-2005, 11:54 AM
Chris -

Contact me offlist at the email address below, and I'll tell you what I was able to learn. Once we find which direction you plan to go, we can summarize the results and bring the results back here. Lots of rather uninteresting details for general Stamp List conversation http://forums.parallax.com/images/smilies/smile.gif

Regards,

Bruce Bates
bvbates @ usamailbox.com

allanlane5
06-20-2005, 11:47 PM
The IR-Buddy throughput is very low (like 100 baud) you probably wouldn't want to use it.

The BS2 can use IR-LED signalling at both ends at 1 mSec or 2 mSec per bit, for a 500 to 1000 bit/sec rate.

The BS2 also supports RS-232, so it could support an on-board 555 based oscillator sending a 'pulse' for zero and silence for a 1 -- the reciever coding might be a little difficult.

It looks like getting an appropriate connector and recieving/transmitting device for your fiber might be difficult.

menehune1
06-21-2005, 12:58 AM
Do you have any Plastic optical fiber (http://www.thefoa.org/tech/pof.htm) suppliers you can purchase from? POF cables are large diameter (.900), relatively inexpensive and I believe they can use standard LEDs as emitters and detectors. Short runs are perfect for POF due to the lossy characteristics of the cable. POF is also being used in automobiles for data networks.
The cables I used years ago could be cut with a hotknife, no polishing required like glass fibers and the bulkhead connectors could be re-used-just unscrew the crimp portion, remove the cable, insert a new cable, tighten.

Ross-O
07-11-2005, 02:53 PM
Hi Guys,

I also need to be able to communicate between 2 stamps via fiber. I'm working with high voltage and need to send 3 relay commands to the device and read the voltage back from the device. I've looked at the B&B RS232-Fiber Optic Modems but they seem a bit pricey at ~$150 per end. http://www.bb-elec.com/product_family.asp?FamilyId=36

I could do this wirelessly but the thought of glitches scares me when controlling 60KJ.

Any thoughts on how to do low speed serial between 2 stamps via fiber inexpensively?

Thanks,
Ross