I need to detect an object up to a distance of 8 inches 3 times per second with a power budget of 0.1 mW average. I am using a VL53L0X and I have been trying to lower the power consumption without much success. Can somebody help me with this?

[Tony L.]

I have a design ready to go but it needs to work for 3 years using 4xAA alkaline batteries. My company has planned 500K pcs/yr. I would really appreciate any help with this.

Thanks,

AL

[John E KVAM]

I think you are using the wrong sensor. The VL6180V1 is the best short-distance sensor. More accurate, less power.

And the key is the Early Escape of the VL6180V1.

So a quick lesson on power…

When the sensor is ranging it’s going to use 20mA.

And a normal range will take about 10 ms.

If you want to range 100 times per second, you will consume the entire 20mA.

So, to save power we have some features.

1. Don’t range so often. 3 times a second is fine for a presence application. Latency goes up, but that’s not bad for a button push.
2. There is an early escape. It’s not really an error, but a notification that there was no target.
   1. 0.5ms into the range, if no photons are returned, the sensor just quits.
   2.  

3 x 0.5ms X 20mA = 0.03mA

And that’s steady state with no target.

If there is a target within a foot or two the power consumption would be

20mA X 3 X 10ms which is 20X more.

This is just a really quick evaluation, but it should be reasonably close.

[Tony L.]

John,
Thanks for answering to my question. I have several issues with this system and one of them is that there is always an object near by and only needs to trigger a measurement if it is in the detection range. I thought that the VL53L0X could work in a similar way as the VL6180 and if the photons do not reach the sensor in the “in range time�? will stop the measurement. I know it can be done but I don’t have enough information to do it. Sometimes, we need to be able to measure up to 24�? (61 cm) so that disqualifies the VL6180.
I spent quite a bit of time translating and reducing the size of the VL53L0X libraries to fit in a PIC18 with 8K of flash memory and I really would appreciate any idea that can help.
Besides the power issue, the VL53L0X works flawlessly with a very good precision and repeatability.
Thanks,
Antonio Lopez

[John E KVAM]

The L0 code has in it a MSRC (Minimal Signal Rate Check) and that's the thing that is supposed to shut down the range if no photons are detected.

We deprecated the MSRC in the data sheet, as it was difficult to tune.

But the code is in our distribution and you can certainly give it a try.

The way to tell if it's working is to keep track of the start time. If the answer comes back in less than 1ms, you know the MSRC caused the range to abort.

I cannot promise that it's flawless however - that's why we removed it from the datasheet.

• john