Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com, has 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.
We make every effort to link to original material posted by the designer. 
Please let us if you would like us to link to or post your design.

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, November 30, 2017 07:43 AM

List of Dave's Circuit Designs

The contents & graphics of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB SITE server


Optical Fiber Pressure & Motion Test
By: Dave Johnson

Optical fibers have been used for detecting motion and pressure for quite a few decades now.  If you would like to experiment with this interesting technique, you can use the circuit below.

The circuit uses an off-the-shelf bright red LED light source, designed for plastic optical fibers.  It also uses a matching phototransistor light detector.  The devices are designed for plastic fiber.  I would suggest you keep the total fiber length less than 50 feet.  Bending or stepping on the fiber will produce a detectable output signal.

This method relies on the phenomenon of “microbending.”  Light is routed through the fiber more efficiently when the fiber is perfectly straight.  When it is forced to move through small angles, a bit of the light is lost through the sides.  When the fiber cable is moved or when pressure is applied, small changes in the intensity of the light detected can be observed.  This technique has been used to monitor ground motion caused by humans and vehicles.

The circuit is powered by a +5v source.  A single resistor, R1, controls the LED current. The Amplifier circuit has a low DC gain but a high X100 gain to AC signals.

 

Click on Drawing Below to view PDF version of Schematic

DC Magazine, Issue 1-2011, Page 4:  Optical Fiber Pressure & Motion Test Circuit

List of Dave's Circuits
List of Circuits from DC Magazine

eMail David A. Johnson, P.E. about this circuit


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |    Privacy Policy


Copyright  January, 1998 - November, 2017     David A. Johnson & Associates.  All Rights reserved. 


 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.