Add a class for Apogee Sunlight Sensor

[aufdenkampe]

SWRC has deployed several of these sensors, and LimnoTech is about to deploy one in the next weeks. SQ-212: Amplified 0-2.5 Volt Sun Calibration Quantum Sensor https://www.apogeeinstruments.com/sq-212-amplified-0-2-5-volt-sun-calibration-quantum-sensor/

@SRGDamia1 , can you work with @s-hicks2 to add a class for this sensor?

[s-hicks2]

It's really simple. Just do an aux analog measurement with the ADS1115 and record the voltage. 1ma equals 1 PAR. I think maybe I did some averaging over a several second period, but the function is similar to the OBS function but simpler because there's no calibration formula.

On Jun 1, 2017 3:25 PM, "Anthony Aufdenkampe" notifications@github.com wrote:

SWRC has deployed several of these sensors, and LimnoTech is about to deploy one in the next weeks. SQ-212: Amplified 0-2.5 Volt Sun Calibration Quantum Sensor https://www.apogeeinstruments.com/sq-212-amplified-0-2-5- volt-sun-calibration-quantum-sensor/

@SRGDamia1 https://github.com/srgdamia1 , can you work with @s-hicks2 https://github.com/s-hicks2 to add a class for this sensor?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/EnviroDIY/ModularSensors/issues/54, or mute the thread https://github.com/notifications/unsubscribe-auth/AFBvGsmzwW77SvKaEbRUxq3fAe-BPY9Vks5r_xAsgaJpZM4NtblZ .

[aufdenkampe]

@SRGDamia1 and @s-hicks2, I got an example sketch working, here: https://github.com/EnviroDIY/ModularSensors/tree/Apogee_SQ-212/sensor_tests/Apogee_SQ212_AnalogTest

It's based on https://github.com/EnviroDIY/ModularSensors/tree/master/sensor_tests/mayfly_turbidity_test1

It works, but the one thing I can't figure out is why divide the measured ADC registers by 17585?

In the typical examples for Arduino., I get why one divides by 1023 for the built-in 10-bit ADC (i2^10-1 = 1023), but we're using the 16-bit ADS1115, so shouldn't we be dividing by 2^16-1, or 65535?

One reason why I'm skeptical is that when I use 17585, I was able to max out the detector with the LED flashlight on my phone. When I used 65535 the values were about 300-600 Einsteins (μmol m-2 s-1), which seems more likely.

[s-hicks2]

The ADS1115 has a variable gain option. We usually use it in the default setting (which is 2/3 gain). If you look at the example code for the ADS1x15 library, you can see in the comments that the resolution of the default setting is 1 bit = 0.1875mV

On the Mayfly, the supply voltage of the converter is 3.3v, so a full-scale signal would be 17585 bits. I came up with that number on my own several years ago through experimenting , but I've seen other people who derived it using similar methods, though some use 17600, which might be mathematically correct, but measurements with a precision voltmeter showed 17585 to be a more accurate number to use.

You can test this by running the following sketch with a standard1.5v alkaline battery connected to the AA2 pin of the Mayfly. You should get around 1600mV for a brand new battery:

include

include

Adafruit_ADS1115 ads; / Use this for the 16-bit version /

void setup(void) { Serial.begin(9600); ads.begin(); }

void loop(void) { int16_t adc2; adc2 = ads.readADC_SingleEnded(2); float voltage = (adc2 * 3300.0)/17585.0; Serial.print("AIN2 bits: "); Serial.print(adc2); Serial.print(" Voltage: "); Serial.print(voltage); Serial.println("mV"); " delay(1000); }

On Mon, Jun 5, 2017 at 1:24 AM, Anthony Aufdenkampe < notifications@github.com> wrote:

@SRGDamia1 https://github.com/srgdamia1 and @s-hicks2 https://github.com/s-hicks2, I got an example sketch working, here: https://github.com/EnviroDIY/ModularSensors/tree/Apogee_SQ- 212/sensor_tests/Apogee_SQ212_AnalogTest

It's based on https://github.com/EnviroDIY/ModularSensors/tree/master/ sensor_tests/mayfly_turbidity_test1

It works, but the one thing I can't figure out is why divide the measured ADC registers by 17585?

In the typical examples for Arduino., I get why one divides by 1023 for the built-in 10-bit ADC (i2^10-1 = 1023), but we're using the 16-bit ADS1115, so shouldn't we be dividing by 2^16-1, or 65535?

One reason why I'm skeptical is that when I use 17585, I was able to max out the detector with the LED flashlight on my phone. When I used 65535 the values were about 300-600 Einsteins (μmol m-2 s-1), which seems more likely.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/EnviroDIY/ModularSensors/issues/54#issuecomment-306105887, or mute the thread https://github.com/notifications/unsubscribe-auth/AFBvGsicoIzN1LoP4F9AnEL_R6ooV6AKks5sA5EOgaJpZM4NtblZ .

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Shannon Hicks Research Engineer Stroud Water Research Center 970 Spencer Road, Avondale, PA 19311 Tel: 610-268-2153 ext. 267 Fax 610-268-0490shicks@stroudcenter.org

[aufdenkampe]

@s-hicks2, thank you! This was very helpful. I'll record all of this in some documentation that I'm working on in the Apogee_SQ-212 branch of this repo.

[aufdenkampe]

I got it all working as a new set of .h and .cpp files in the modular code! I created a pull request (#56) to merge into the Develop branch.