This is the TSL235R light-to-frequency converter from Texas Advanced Optoelectronics Solutions. When The Frequency to light converter detects light, it outputs a square wave (50% duty cycle) with frequency directly proportional to light intensity. 

The device has been temperature compensated for the ultraviolet-to-visible light range of 320 nm to 700 nm. The TSL235R can be powered at anywhere between 2.7 and 5.5V, and will typically pull about 2 mA of current. 

It comes in a simple, 3-pin through hole package. No external components are necessary to use the converter, and the digital output allows direct interface to a microcontroller / arduino or other logic circuitry.

Features

• High-resolution conversion of light intensity to frequency with no external components
• Communicates directly with a microcontroller or arduino
• Voltage range from 2.7 to 5.5 V
• Nonlinearity error typically 0.2% at 100kHz
• Stable 150 ppm/°C temperature coefficient

For Frequency to light converter datasheet, please click here

For how to use light to frequency converter with arduino and code, click here