UV Sensor VEML6075 - Very Low UV Index Value - even in full sunlight

Sensors Environmental
1

HI,

I’m using the Sparkfun UV Sensor VEML6075 with a WEMOS D1R2 ESP8266, the ssnor is powered from 3.3v and confirmed correctly connected with the I2C_Scanner.ino sketch (address 0x10).

All the Sparkfun Arduino example run OK, however the UV Index value is consistently very, very low - in the range of 1.5-3 even in full midday sunlight in the Australian summer (ambient temperature 33degC, full sunlight, local weather bureau reporting UV Index of 9 == VERY HIGH).

I don’t think this is a simple calibration issue, as the values are so far from the expected value.

Thoughts? Help please?

thnx

billd :?:

2

Hi billd.

Our code for this was written for an Arduino Uno and I’m thinking that somewhere in the calculations needed to obtain UV Index, the WEMOS board is having issues.

Can you try the same code on an Uno and see if that fixes things?

3

HI Chris,

Thnx for info, yes, I’ve just confirmed the same results with UNO (I tried two different UNO boards to confirm).

Here’s a sample of the ExampleZ_VEML6075_UV_Test.ino serial monitor output:

Evening Sun - moderate cloud - official index is 8 . . .

434.28, 13.50, 390, 324, 0.25

486.57, 55.65, 398, 339, 0.31

504.00, 73.80, 396, 336, 0.33

456.78, 24.50, 400, 334, 0.27

435.86, 9.75, 395, 328, 0.25

403.55, -28.20, 401, 331, 0.21

498.42, 52.55, 411, 352, 0.31

433.66, 26.60, 382, 310, 0.26

437.70, -17.55, 449, 344, 0.23

438.16, -52.70, 566, 404, 0.21

547.43, -54.30, 559, 423, 0.27

506.92, -56.25, 485, 386, 0.25

434.93, -56.20, 451, 345, 0.21

419.52, -85.90, 482, 368, 0.18

426.47, -43.55, 424, 325, 0.21

384.95, -68.45, 446, 321, 0.17

426.56, -46.55, 439, 342, 0.21

422.58, -45.70, 436, 350, 0.21

432.07, -130.25, 550, 421, 0.16

446.49, -110.45, 536, 423, 0.18

432.04, -135.75, 535, 422, 0.16

423.90, -113.75, 505, 400, 0.16

440.79, -48.20, 441, 343, 0.21

462.46, -30.95, 421, 324, 0.24

496.99, -52.05, 474, 381, 0.24

422.77, -89.70, 481, 377, 0.18

399.02, -71.15, 437, 348, 0.18

428.23, -63.35, 468, 357, 0.20

421.86, -31.05, 399, 292, 0.21

423.30, 36.90, 308, 218, 0.26

Now with a handheld UV flashlight shining on the sensor . . .

14.34, 11.15, 3, 0, 0.01

12.34, 10.15, 3, 0, 0.01

10.78, 10.05, 1, 0, 0.01

1382.40, -37.50, 130, 0, 0.74

1620.44, -38.60, 148, 0, 0.88

2099.98, -52.45, 191, 0, 1.13

2400.60, -61.00, 220, 0, 1.30

2192.78, -52.95, 201, 0, 1.18

1809.04, -46.60, 168, 0, 0.98

1792.14, -39.85, 163, 0, 0.97

1849.04, -42.60, 168, 0, 1.00

1916.50, -47.25, 175, 0, 1.04

1789.14, -43.85, 163, 0, 0.97

1687.90, -41.25, 155, 0, 0.91

2007.32, -56.30, 194, 0, 1.08

2240.16, -65.90, 222, 0, 1.20

2174.26, -61.15, 217, 0, 1.17

2702.28, -85.20, 276, 0, 1.45

1434.38, -28.95, 121, 0, 0.78

768.24, -7.10, 58, 0, 0.42

2202.64, -46.60, 188, 0, 0.78

2532.02, -72.05, 259, 0, 1.36

1611.40, -25.00, 180, 0, 0.88

1077.24, -14.60, 108, 0, 0.59

900.74, -19.45, 91, 0, 0.57

1540.34, -52.35, 153, 0, 0.82

1429.22, -48.55, 149, 0, 0.76

3163.84, -121.60, 328, 0, 1.68

3286.66, -124.65, 347, 0, 1.75

2878.28, -91.20, 276, 0, 1.54

2809.14, -83.85, 263, 0, 1.51

2486.94, -65.85, 223, 0, 1.34

1954.26, -43.65, 167, 0, 1.06

1028.20, -17.50, 90, 0, 0.56

557.22, -4.55, 49, 0, 0.31

300.06, 2.35, 27, 0, 0.17

The sensor definitely detects the presence or otherwise of UV . . . but the values are very, very low.

Thoughts?

billd

4

It sounds like a bad sensor.

If you got this directly from the SparkFun website, fill in the form [on this page and put the URL to this post in the “Why do you want an RMA” section and I’ll get a replacement out to you.

If you got the sensor from a distributor, let them know you have a faulty unit and SparkFun has authorized a replacement and they will be happy to get that replaced for you. :-)](Return Policy - SparkFun Electronics)

5

Thnx Chris,

I’ve been in touch with the local supplier, they have dispatched a replacement sensor.

Thnx

billd