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Comment by lnsru | Hacker News Reader

I really love seeing laser products without any eye safety features. Especially weird when it has range of 120 cm. Why not to use simple and cheap ultrasound sensor without eye safety problems?

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If I had to guess, this doesn’t need to be much more powerful than the lasers at supermarket checkouts. Never heard of eyepro for those.

This is a VCSEL (the part is a VL53L0X) that probably doesn't have as much power as those ferociously bright blue LEDs which you can see across the room. (Checking the datasheet this seems to be true: max current is 20mA and it doesn't seem to be particularly well focused)

You don't use ultrasound because it has both resolution and absorption issues.

> You don't use ultrasound because it has both resolution and absorption issues.

I've used both these laser sensors and those dirt cheap ultrasonic sensors in many projects. The ultrasonic ones would work just as well in this application, and be 10x cheaper. The biggest difference is the size, as the ultrasonic ones are pretty bulky in comparison.

I'm not sure what experience you've had with them, but I've also done the same and interfaced with both types of parts in the past. My personal experience is that you seem to get what you pay for — while ultrasonic sensors are incredibly cheap they're also often fairly inaccurate, much more than the VL53L0X. Both parts have their use cases but it seems to me that the original creator of Daytripper probably valued that accuracy over the increased BOM cost by a few dollars.

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