Motion detection without microcontroller and interrupt generation by sensor VL53L1X battery operated CR2045

[Oxford Electronics]

I am developing a device that runs on a CR2045 battery, I need a sensor for determining the direction of people movement and counting, I choice VL53L1X. My question is: can this sensor detect movements autonomously without a microcontroller and generate an interrupt if there is no movement to sleep and consume very little power. I need low consumption around the clock about 5-10 microamps

[John E KVAM]

I've tried to get this sensor to use lower power. And there are things one can do.

But the hard limit is that while the sensor is ranging the device consumes 20mA. It's the generation of the laser light that is using the power.

1) You can lower the number of times per second one ranges. But this increases latency.

2) you can decrease the amount of time each range takes - but this reduces the accuracy.

3) if using the VL6180 or the VL53L0X one can use the early escape or Minimal Signal Rate Check.

• This ends the range early if no photons are returned. Only uses the laser for 0.5ms before shutting down.

My rule of thumb...

20mA * ranging time (in seconds) * ranges per second.

So one might use:

20mA * 0.010 * 3 = .6mA or about 1.8mW.

And that might work to detect a hand under a faucet for instance.

But if most of your ranges are out into space (and you are using the VL6180 or VL53L0X) it's

20mA *0.0005*3 = 0.03mA for the ranges without a detect.

But will it get down to 5-10 microamps?

No. I'm sorry one simply cannot create an active sensor with that power budget.

• john