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

DiscoverCircuits.com has links to 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.

HOME Schematics Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches
Welcome to DiscoverCircuits.com - online since 2002

See Media Kit for
Advertising Opportunities

Attention Designers:  Please alert us by eMail if we have linked to sites
where your original material has been copied without your permission.
We will change to the LINK to your site.  
Thank you.


Circuit Solutions Notebook
Last Updated On:  Tuesday October 24, 2017

Latest Technical Challenge           Previous Circuits Solutions           Circuit Solutions in Progress

Clear Fluid Detector


Devise a circuit which can determine if a one inch diameter piece of clear tubing has alcohol in it or not.


An optical technique seemed like the best choice for this application.  The simple circuit below works well but only when the light detector can be shielded from bright ambient light.  A visible red LED launches light pulses through the side of the clear tubing and emerges at the opposite side.  A phototransistor forms a light detector.  The circuit takes advantage of the lens effect from any clear fluid inside the tubing.  When there is only air in the tubing, the light scatters and spreads out quickly before it reaches the phototransistor.  When the tube is full of clear fluid, it forms a cylindrical lens, focusing more light onto the detector.  By carefully selecting the value of R6, the output voltage appearing at the “Data” input of the flip flop is sufficient to change the state of the device at the trailing edge of the clock pulse.  The second half of the flip/flop is configured into a pulse generator.  The average current of the circuit draws only about 10 microamps, so it can be powered from a battery for many years.




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

Discovercircuits.com endeavors to credit original designers.   Please alert us by eMail so we can
delete links to material that have been copied without your permission
.   Thank you.

© Copyright of all original material on this website is the property
of David A. Johnson, P.E. (Dave Johnson & Associates ) unless otherwise noted.  

Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.
All material is provided "as is" without guarantees or warranty of any kind, either expressed or implied.