------Question for SUF268J001 Please Put your question below------
I am trying to integrate the solar radiation sensor SUF268J001 into my design. But when I try to check the functionality of the sensor, it keeps outputting 0.6V with or without radiation. I am following the circuit provided in the data sheet using voltage divider to measure the voltage. The pull-up resistor R1 is 10k Ohm and R2 is 100 Ohm.
Did I do something wrong with the resistor dimensions or is the sensor broken ?
Hello @khairi.wankadir,
The resistor values seem appropriate. The 10 kΩ resistor should drop about 4 VDC when the sensor is pulling 0.4 mA. (Your microcontroller should see this as a 1 VDC signal assuming a 5 VDC voltage rail.)
By chance, is the sensor installed backwards? If forward biased, I would expect to see this constant 0.6 VDC signal.
Happy soldering,
APDahlen
Hi @APDahlen ,
Thanks a lot for the reply. I was focusing on the circuit and totally forgot that the sensor itself is a diode. Your reply helped a lot!
Can you please advise which formula you would use to convert the measured voltage to solar radiation W/m2 ?
I found several formulas online, but none is comparable with the value of my solarimeter currently.
Hello @khairi.wankadir,
That is a challenging question. This is what we know:
The sensor was analyzed against a tungsten 2856K source.
2856K Standard A light source, 767.4 (W/m2) or 17,359 (LUX).
The sensor has a pronounced sensitivity to color (curve included below). For reference, note that the human eye is sensitive to 380 to about 750 nm. The sensor peaks at 925 nm (invisible near-infrared).
Linearity response to LUX is it implied by the chart (below). However, this is only true for a constant light spectrum.
This will be challenging for your project as the test lamp includes infrared content—a type of energy to which the sensor is most sensitive.
Two thoughts:
Change the sensor. As a point of reference, refer to the spectrum of this OSI Optoelectronics PIN-10DF sensor.
Obtain a solar equivalent LED source and construct your own radiation curves. Calibrate to truth by observing the sensor’s response on a bright sunny day. Consider adding an IR filter.
Happy soldering,
APDahlen
