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.

 

DiscoverCircuits.com -- Hobby Corner
Last Updated on: Wednesday, October 18, 2017 05:04 AM

Hobby Circuits List

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

More  Voltage to Frequency Converters
        Freespace Communications  VCO Circuits     
Light Sensor Circuits

Light to Frequency Converter
designed by David A. Johnson, P.E.

This circuit uses a CMOS version of the classic 555 timer, to form a light intensity to frequency converter.  A small PIN photo diode is used as the light detector.  The pulses produced are short, so in some applications you may want to stretch them or feed them through a flip/flop to produce a square wave signal.  Although the circuit shown is designed for a 5v supply, it could operate from almost any voltage from 3v to 15v.
The 555 timer circuit is configured as a free running oscillator.  When a PIN photodiode is reversed biased, it leaks current proportional to the light intensity hitting lt.  The photodiode leakage current charges the 0.01uF capacitor.  When the voltage of the capacitor reaches about 2/3 of the supply voltage, the pin 3 output of the 555 timer swings low.  This state quickly discharges the capacitor through the photo diode, until the capacitor voltage is less than 1/3 of the supply voltage.  This causes the pin 3 output of the 555 to swing high again, for another charge cycle.  With the component value chosen, the frequency of the oscillator will range from about 1Hz in total darkness to about 25KHz in sunlight.  Other frequencies are possible by changing the value of the 0.01uF capacitor.

Click on Drawing Below to view PDF version of Schematic

Circuit Light to Frequency Converter designed by David Johnson

More  Voltage to Frequency Converters      
 Freespace Communications 
VCO Circuits    
 Light Sensor Circuits

Hobby Circuits List
eMail David A. Johnson, P.E. about this circuit

 


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.