OPT3001: Led pulse counting

Hi Rustem,

OPT3001 typical current is 0.3-0.4uA in shutdown, 1.8uA in dark conditions, and 3.7uA under 83klux. You can hit your current requirement if you reduce the polling rate of the sensor to keep it in shutdown for some of the time. However, OPT3001 has an integration time of 100ms and so will not be able to do 20Hz capture. I'm not sure we will be able to hit the current and sample rate requirements with an ALS. Are you able to make a trade off on either?

Best,

Alex

Hello! Thank you for a quick answer!

Unfortunately, If i will wake up MCU every 50 ms to turn on/off OPT3001, overall current will be high. I can do the same thing without OPT3001 (with phototransistor).

10Hz is not so good, but also acceptable. But i need < 1uA from sensor without additional current expenses on MCU side. 

Hi Rustem,

Is the MCU going to sleep in your application? If the OPT3001 is continuously collecting data at 10Hz won't the MCU need to still be awake to read the data? I don't follow how the MCU can sleep in this configuration where continuous capture is required. I would think the MCU would need to wake up every 100ms to read data. To reduce current the OPT would need to wake up every 200ms, which would require the MCU to wake up every 200ms, which is 50% less than the case for continuous data capture (no sleeping) where the MCU would need to wake up every 100ms.

Conversion time of OPT3001 is 100ms integration plus 3ms conversion. This gives you 9.7Hz. What are your ambient light conditions? The photodiode current inside the OPT3001 changes given the light intensity so you will see higher current at higher light conditions. As I noted the datasheet states 1.8uA powered-up and collecting data (not shutdown) in dark conditions. If you are in indoor conditions (~200 lux) then current should still be around this level (not the 3.7uA for 83k lux, which you need a very bright light source to get). If you really need to get to 1uA the OPT needs to capture less frequently. To give a ballpark, if you half the sample rate to 4.85Hz the OPT will capture for 100ms, sleep for 100ms, then capture again. Then the current will be ~1.8uA half the time and ~0.3uA the other half. This gives you 1.05uA total.

Please let me know if this sounds like a viable option and if the MCU can be used in this way. If so we may also need to check the OPT3001 current at 100ms conversion as the datasheet specs the current for 800ms conversion setting.

Best,

Alex

Hello, Alex!

MCU is sleeping most of the time. It's waked up only by interrupt from the sensor, then sensor detects light.
I found the solution with low-power phototransistor (L3DP3C).
Thank you for your attention, anyway!

Thanks Rustem. I will mark the thread as closed.