Technology Connections
2 HN recommenders · recommended in 4 months, 2024–2026
11:18 · 1.8M views · Apr 29, 2024
Technology Connections explains how automatic windshield wiper rain sensors work, using an infrared light source and total internal reflection in the glass.
Brought up in Tesla auto-wiper threads as the clear explanation of how simple conventional rain sensors work.
4 comments from Hacker News
> The parking sensors basically don't work at all due to being vision only - and apparently can't be made to work properly What's stupid about this is that it is hard to come up with a good reason for it. The no LIDAR thing is at least understandable because at the time LIDAR was very expensive. Ultrasonic parking sensors are cheap. Same for automatic windshield wipers, which have been a significant source of complaints from Tesla owners. Pretty much everyone else uses a dedicated sensor that is simple and inexpensive and works well. Technology Connections has a good video on how it works [1]. Tesla uses vision. [1] this video
For anyone curious, Technology Connections has a good video on how traditional automobile rain sensors work: this video
I'm baffled by Tesla's approach to this. There are two ways cars currently do automatic wipers. One way uses a very clever, simple, cheap but very effective sensor. Technology Connections did an episode [1] a few months ago on these sensors. The electronics in it are just a couple infrared LEDs and infrared photodiodes. The other way is to use a camera, such as the camera you already have for your driver assist functions, and try to use computer vision software to figure out how much rain there is. Pretty much everyone except Tesla uses the first way. Tesla uses the second way. What baffles me is that of the three options they might have pursued: 1. Use a rain sensor like the ones everyone else uses, 2. Use a camera and computer vision software which doesn't work as well, and 3. Do not have automatic wipers, it seems to be that #2 is the worst option. Automatic wipers aren't really needed. Once you get used to where the controls are and how they work on a car without automatic wipers adjusting your wipers for the current conditions becomes one of those things you do completely unconsciously. So if my next car, like my current car, does not have automatic wipers it is not going to bother me. But if it has them and the don't work well, that very likely will annoy me, at least until I get tired of having to manually intervene and turn auto mode off or until manual intervention becomes something that I do unconsciously and so forget about them. In either case I end up back in a s
The wiper system has nothing to do with self-driving -- it's based on total internal reflection in the glass: this video