VEML6070 and VEML6075 UV sensors

[korttoma]

Did anyone measure the current consumption of these VEML chips?
I just compared a Sensebender Micro with the VEML6075 to a standalone Sensebender Micro and the standalone one measured 28uA and the one with the VEML6075 measured 740uA.

I just checked the VEML6075 documentation and typical consumption is 480uA but it should also be possible to shut it down and then it should only draw 800nA.

I need to check the Lib if there is some function to shut it down and wake it up. Or else I will try to change the setup so I can power the VEML6075 from an output pin so I can turn it completely off.

[scalz]

@korttoma
if i remember, sleep is not implemented in the veml6075 lib above. I added a sleep function and set the corresponding CONF register. not a big thing ;)

[korttoma]

@scalz please share your sleep function implementation :D it is quite a "big thing" for a non programmer.

[scalz]

@korttoma you can try this, and you'll see it's not a big thing :smile:

in your .h, in the public section, add this:

void sleep(bool mode);

then in the .cpp, add this:

void VEML6075::sleep(bool mode) {

	if (mode) 
		this->config |= 1; // Go to sleep			
	else 
		this->config &= 254; // Wake up
	
	this->write16(VEML6075_REG_CONF, this->config);
	
}

In your sketch, just do this:

veml6075.sleep(true); // power down veml6075

Note: i added this because i noticed it wasn't implemented, but i've not checked the power consumption yet. So if you can tell me if it's ok, please!

Enjoy ;)

[korttoma]

@scalz thanks for the sleep function! The current consumption is now down to 85uA but the problem is that onece it sleeps I cant get it to wake up.

Tried with:

veml6075.sleep(false);

Tried allso adding a 500ms sleep after the wakeup to give it time to setle.
But do I need to do something more?

[scalz]

@korttoma sorry for the copy/paste mistake :) you can try again, i've updated above. maybe someday i'll measure power consuption of a sensebender, weird that you get 28uA for the standalone..

[korttoma]

@scalz seems to be working now :D don´t take my current consumtion figures to sareously since Im using the Micro (nano) ampere meter and I realy have nothing good to calibrate it against.

[alexsh1]

I have a strange problem. VEML6070 is showing UV Index 6, which is more or less in line with other online sources. VEML6075 is showing UV index 10.5, which is wrong. I'll double check the sketch once more but cannot understand where this error comes from

[korttoma]

I mounted the Sensebender Micro VEML6075 inside my old broken UVN800 and set it in the roof. Here are graphs of the values I received the last 3 days. Unfortunately I do not have anything to compare with but the values seem reasonable.

[alexsh1]

@scalz FYG, I am using VEML6075 without sleep and it works now for nearly a year on 2xAA. I am still puzzled though by Index difference 6070 and 6075

[korttoma]

Yeah, my 6075 device is also still working fine on the 2xAA batteries I put in it a year ago.

[alexsh1]

OK, I think found what the issue is. VEML 6070 is not providing accurate UV Index. Adafruit is stating the following:

Note that this is not UV index, its just UV light intensity!

This is how it can be converted into sort of UV Index according to the datasheet:

RISK_LEVEL convert_to_risk_level(WORD uvs_step)
{
WORD risk_level_mapping_table[4] = {2241, 4482, 5976, 8217};
}

WORD read_uvs_step(void)
{
BYTE lsb, msb;
WORD data;
VEML6070_read_byte(VEML6070_ADDR_DATA_MSB, &msb);
VEML6070_read_byte(VEML6070_ADDR_DATA_LSB, &lsb);
data = ((WORD)msb << 8) | (WORD)lsb;
return data;
}


LEVEL* UV Index 
===== ======== 
LOW 0-2 
MODERATE 3-5 
HIGH 6-7 
VERY HIGH 8-10 
EXTREME >=11

[alexsh1]

@korttoma @scalz FYG I got a new DMM from Dave Jones 121GW and decided to measure a sleep current for VEML6075 and to my surprise:

Quickly reading the datasheet I discovered my mistake:

• current supply - 480uA
• shutdown current - 800nA

Therefore, the sensor has to be put to sleep properly.
One can modify the existing lib:

uint8_t VEML6075::Shutdown() {  //Places device in shutdown low power mode

	Config = ReadByte(CONF_CMD, 0); //Update global config value

	return WriteConfig(Config | 0x01); //Set shutdown bit

}



uint8_t VEML6075::PowerOn() {  //Turns device on from shutdown mode

	Config = ReadByte(CONF_CMD, 0); //Update global config value

	return WriteConfig(Config & 0xFE); //Clear shutdown bit

}

Make sure you define #define CONF_CMD 0x00

PS Now I understand why I did not change batteries - they are rechargeable. Charing and putting them back made me think that batteries lasted for a long time. :relaxed:

[alexsh1]

I have now three sensor from Vishay - VEML6040, VEML6070 and VEML6075
I can confirm all three sensors must be property put down to sleep with battery nodes or you would have the following sleeping currents on nodes with typical mysensors setup and standalone sleeping current of 4uA:

VEML6040 - 240uA
VEML6070 - 94uA
VEML6075 - 622uA

Unfortunately, most libraries do not care for properly sleeping/waking up sensors and therefore, one has to do a little tinkering with software to make it work. I am actually thinking about re-writing some libs completely.

[Avamander]

Battery issues is one thing, SparkFun's VEML6075 library can't handle direct daylight even (compensated UV readings go negative).

[alexsh1]

@avamander That's impossible - it is designed to handle the direct sunlight. Mine is showing UV Index = 9. Negative UV reading is a software issue - looks like Sparkfun did not write a good lib for it. Did you try a different lib?

[Avamander]

@alexsh1

Did you try a different lib?

Haven't bothered, I'm just logging the raw values and then compensating with software.

[alexsh1]

@avamander It definitely works.

My problem for now was just the battery consumption. I have one of these:

https://www.aliexpress.com/item/I2C-Interface-3-3V-Board-Based-on-VEML6075-UVA-UVB-Light-Sensor-Module/32832979057.html?spm=2114.search0104.3.1.5f765e65b6nG8K&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10151_10065_10344_10130_10068_10324_10342_10547_10325_10343_10340_10548_10341_10696_10192_10190_10084_10083_10618_10307_10820_10301_10821_10303_10059_100031_10103_524_10624_10623_10622_10621_10620,searchweb201603_25,ppcSwitch_7&algo_expid=c6a42de3-1e19-435c-af06-c3a9b24d4ca3-0&algo_pvid=c6a42de3-1e19-435c-af06-c3a9b24d4ca3&priceBeautifyAB=0

The problem is that it is dodgy - the sleep consumption never goes below 50uA at 3.2V. According to the datasheet it should be 800nA while sleeping at 1.8V and 25C. Can anyone measure a shutdown current for VEML6085 please?

[Avamander]

@alexsh1 I have the same board, there seems to be a regulator and a few other components on the board, if you remove those, how's the power consumption then?

[alexsh1]

@avamander I have removed every component bit by bit. Originally the consumption was 56uA and now it is 50uA with the only sensor left on the board