Re:Former Tesla Firmware Engineer Discusses the System
by Cyph0n on Friday August 24, 2018 @09:25PM
(#17839040)
It's not a pressure sensor, but an induction loop. Basically, there is a coil placed on the road that has a small AC current passed through it. When a car (metal) sits on top of the coil, the two "coils" couple, changing the overall inductance. A simple sensor can detect this change.
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Re:Former Tesla Firmware Engineer Discusses the System
by TheKarateKid on Saturday August 25, 2018 @01:24AM
(#17839681)
The current is even able to pass through the tires?
Re:Former Tesla Firmware Engineer Discusses the System
by Cyph0n on Saturday August 25, 2018 @02:26PM
(#17841873)
No, the current passes through the coil, and the coil has no physical contact with the vehicle.
Look up inductive coupling. The basic idea is that a changing (AC) current in a conductor generates a changing magnetic field (Ampere's law). This changing magnetic field then induces a voltage in the second conductor (Faraday's law). This is the principle behind how transformers work.
Re:Former Tesla Firmware Engineer Discusses the System
by Dreami on Saturday August 25, 2018 @03:12AM
(#17839943)
As far as I understand, it's just electromagnetic waves. No current passing through to the car, but the coil can "register" a change in its magnetic field and can determine that it's a car and how fast it goes
Re:Former Tesla Firmware Engineer Discusses the System
by vageli on Saturday August 25, 2018 @11:56AM
(#17841297)
Can confirm. Also interesting to note that motorcycles often have trouble triggering these sensors (a common trick is to stick a heavy duty magnet underneath).
Re:Former Tesla Firmware Engineer Discusses the System
by BinaryIdiot on Monday August 27, 2018 @03:00AM
(#17849873)
Really interesting! Thanks for the correction!