The simple, clever sensor behind automatic windshield wipers
Why Hacker News recommends it
Brought up in Tesla auto-wiper threads as the clear explanation of how simple conventional rain sensors work.
What it is
Technology Connections explains how automatic windshield wiper rain sensors work, using an infrared light source and total internal reflection in the glass.
Recommended by 2 HN commenters across 2 different months, 2024 to 2026.
What Hacker News said
Recommends Stratoscope · 2024-05 · on “Tesla Auto Wipers: Why They Don't Work and Why There Isn't an Easy Fix”
For anyone curious, Technology Connections has a good video on how traditional automobile rain sensors work: [this video]
Recommends tzs · 2026-01 · on “Tesla is committing automotive suicide”
> 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]
Cites tzs · 2024-09 · on “Tesla Full Self Driving requires human intervention every 13 miles”
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 e
Cites gcanyon · 2025-09 · on “Tesla changes meaning of 'Full Self-Driving', gives up on promise of autonomy”
The wiper system has nothing to do with self-driving -- it's based on total internal reflection in the glass: [this video]