uv sensor circuit

GUVA-S12SD UV Sensor Module & Circuit

UV sensor module photo 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)*

Standard UV Index vs Sensor Modules Output Voltage

(* World Health Organisation Classification / Standard UV Index vs Sensor Module’s Output Voltage)

Inside Electronics

The UV Sensor module is based on the renowned sensor GUVA-S12SD from EOC ( . 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 ( 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.

GUVA-S12SD SGM8521 pinouts

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!

uv sensor circuit


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  • makksmail-ru

    Perhaps this is no longer relevant, but it seems that I know how to solve the problem of R. Niestroj.The circuit is a current generator. This current is amplified by oy. According to the datasheet, the sensor issues 26 nA for 1 UVI. Thus, at 10 UVI the sensor will output 260 nA. We know that the circuit at the output gives 1 V at 10 UVI. So we got the gain factor. 260 nA corresponds to 1 V at the output.
    It is necessary to remember that the UV index is an integral parameter. Different wavelengths of the UV spectrum of the sun affect the human skin differently. The sensor is designed with this erythema curve in mind. For artificial UV sources for different wavelengths, a different slope will result for the dependence of the photocurrent vs power. In datasheet there is such a dependence for a wavelength of 352 nm. It shows that at a power of 15 mW / cm2 the current will be about 1700 nA. Now we will make a proportion, substituting that 260 nA gives 1 V. We will obtain approximately 2,294 mW / cm2. For other wavelengths, the slope will be somewhat different. I think it can be corrected from the sensitivity curve in the datasheet for the desired wavelength.

  • R. Niestroj

    Dear Mr. Hareendran,
    for a project I want to use the guva-s12sd board with an arduino.
    I want to get real UV energy measurements in mW/cm^2. The provider of the diode gives a photocurrent of 113 nA per mW/cm^2. How do I get to a reading with the Arduino? Which Voltage relates to which mW/cm^2 value?
    Thanks in advance

    • T.K.Hareendran

      @ R. Niestroj
      The GUVA-S12SD UV Sensor introduced here is a pre-built module comprising GUVA-S12SD sensor from EOC,and SGM8521 op-amp from SGMICRO. Output from this module is 0V to 1V for 0 to 10 UV Index. I’ve no rich experience with any independent UV sensor yet, because I keep myself busy with conducting more experiments using this pre-wired module(s).

      Recently, I bought one more module from, and observed about 1V at UV Index 10. Next is the processing of this Analog Output (0V to 1V) using Arduino UNO to build a UV meter with digital display. Updates will be posted here in due time!


    • R. Niestroj

      Dear Mr. Hareendran,
      thank you for your kindly help. I know the website you mentioned, but they only give the UV-Index, which is not what I want.
      I want to have a exact measuerement of UV radiation of 365 nm in mW/cm^2.
      Therefore I need to know, which voltage value relates to which photocurrent. In the Datasheet of the Diode it means the photocurrent is 113 nA at 1 mW/cm^2. You will find the datasheet here:
      Now is the question: How is the Signal (photocurrent) amplified and relates to which voltage? I will also ask the distributor of this board for some information.
      Thanks for your help.
      Best regards,
      R. Niestroj


      Hope this helps:

      However, I will revert with a detailed note asap…

      Thanks for your keen interest in my article, dear Niestroj !

  • Jim Keith

    Agreed, Rx cannot be 31Ω. Since the op amp is CMOS, the input bias current is essentially zero. As a result, it is ideal for monitoring high impedance photo-diode circuits. Yes, 10M sounds reasonable, but there is no way to measure the in-circuit resistance of such. Perhaps 31M if it is in a high resistance class device…

    • T.K.Hareendran

      Recently I noticed that, the marking on Rx is 01E, not 310. As per EIA Marking Code for SMD Resistors, 01E denotes 1M.

    • T.K.Hareendran

      Dear Mr. Jim Keith

      Thanks for your attention,and feedback!

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