An UV Sensor is used for detecting the intensity of incident ultraviolet (UV) radiation – radiation lying in the ultraviolet range, with wave lengths shorter than light but longer than Xrays. UV sensors are widely used in many different applications, including but not limited to automobiles, pharmaceuticals and robotics. Now a days, a vast range of pre-wired UV sensor modules are readily available for use by amateur and professional design engineers and hobbyists. These microcontroller-compatible modules can be used for detecting the intensity of incident ultraviolet radiation, like the UV radiation in sunlight.
Recently, I bought such a module (photograph of which is shown above) for my next UV electronics experiment, and really impressed by its simple internal circuitry. The module, with typical UV detection wavelength of 200 – 370nm, outputs a calibrated analog voltage which varies with the UV light intensity. Good for interfacing with any MCU through one ADC channel!
The module provides a standard, right-angled, 3-pin male-header interface connection:
1. GND: 0V (Ground connection)
2. VCC: 3.3V to 5.5V (5mA current consumption)
3. OUT: 0V to 1V ( 0 to 10 UV Index)*
The UV Sensor module is based on the renowned sensor GUVA-S12SD from EOC (www.eocinc.com) . GUVA-S12SD is a Gallium Nitride material based Schottky-type photodiode, optimized for photovoltaic mode operation. Next main component is an Op-Amp IC SGM8521 from SGMICRO (www.sg-micro.com). The SGM8521 is a rail-to-rail input and output voltage feedback amplifiers offering low cost. This Op-Amp have a wide input common-mode voltage range and output voltage swing, and take the minimum operating supply voltage down to 2.1V and the maximum recommended supply voltage is 5.5V. Besides, SGM8521 provides 150kHz bandwidth at a low current consumption of 4.7 µA.
Here is the basic circuit diagram of the UV Sensor Module, drawn & checked by me (thanks to my USB microscope and LCR meter).In the circuit PD1 is the GUVA-S12SD, and U1 is the SGM8521. The only one component still leaves room for doubt is resistor RX, value of which is marked as 310 (in some other modules one 10M resistor is used in this place). Help me to figure out, dear readers!