Light to Frequency ICs?

Thread Starter


Joined Feb 19, 2011
Okay well I understand the applications for photo resisters. Those of course are easy to understand, but Light to Frequency? Yes I know it pulses out a "train wave" for microcontrollers and all, but uhhh... What are the applications? Like I kinda want to hear some more examples then just "it can be used for solar panels". Like this is one of the things that kinda stump me.

Like I had some ideas on the functionality, but I've never heard or seen anyone use theses types of ICs. Like it's kinda one of those well you have a photo resister on this side and a IC that almost does the same thing, but pulses frequencies (I'm guesting).

I've pretty much surprisingly found this at a Radioshack here in NJ and I had to buy it so I could play around with it. Honestly I'm surprised they still had something like that sitting in there for years.


Joined Feb 20, 2011
The simplest light-to-frequency converter I can think of would be a photoresistor connected to a 555 timer in place of a regular transistor. For example, take this circuit:

Put the photoresistor in place of R1, and as light changes, the output frequency of the 555 will also change.
I'm not quite sure if this is what you were asking, though :D
Der Strom

Thread Starter


Joined Feb 19, 2011
Thanks, but it's not. I have a TSL230R Light to Frequency converter IC, I just don't understand the uses these things have. Like what could be used for? Compared to a regular photo resister with a microcontroller and what would the IC be used for then using a photo resistor. I'm just not seeing the differences in usage is all.


Joined Oct 2, 2009
A light-to-frequency converter is a brilliant idea and has many useful applications. Think of it as an analog to digital converter, i.e. going from the analog world to the digital world.

A light dependent resistor (LDR), photoresistor, photodiode, or phototransistor can be used in an analog circuit. Many times you want to make an accurate reading of the light source, for example a photometer. With the advent of the microcontroller this has become an easy solution to many problems.

To take a measurement from a photoresistor you would need an analog-to-digital converter. It may be a lot simpler and more accurate to use a light-to-frequency converter instead.

TSL220, TSL230, TSL235 etc. are all examples of light-to-frequency converters made by Texas Instruments but are now obsolete.
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Joined Apr 24, 2011
Even measuring the ambient light level in a room can span a huge range of data, which depending on your application you may want to measure accurately. Even if you just want "dark," "sun just up," "lights on" and "full sun" you may need something better the the 256 or 1024 levels a typical analog to digital converter may give you.

By converting to light the frequency output of this thing is proportional to light levels from .001 to 1000 uW/cm, that is one million to one.

And measuring time is something a micro can be very good at, as good as the crystal running it's oscillator.