JStraw

Here's the scientific explanation (the discussion is about windows, but they explain how the technology applies to mirrors at the end):


Electrochromic windows darken when voltage is added and are transparent when voltage is taken away. Like suspended particle devices, electrochromic windows can be adjusted to allow varying levels of visibility. They are not an all or nothing technology like liquid crystals.
Electrochromic windows center around special materials that have electrochromic properties. "Electrochromic" describes materials that can change color when energized by an electrical current. Essentially, electricity kicks off a chemical reaction in this sort of material. This reaction (like any chemical reaction) changes the properties of the material. In this case, the reaction changes the way the material reflects and absorbs light. In some electrochromic materials, the change is between different colors. In electrochromic windows, the material changes between colored (reflecting light of some color) and transparent (not reflecting any light).

At its most basic level, an electrochromic window needs this sort of electrochromic material and an electrode system to change its chemical state from colored to transparent and back again. There are several different ways to do this, employing different materials and electrode systems.

Like other smart windows, electrochromic windows are made by sandwiching certain materials between two panes of glass. Here are the materials inside one basic electrochromic window system and the order you will find them in:


In this design, the chemical reaction at work is an oxidation reaction -- a reaction in which molecules in a compound lose an electron. Ions in the sandwiched electrochromic layer are what allow it to change from opaque to transparent. It's these ions that allow it to absorb light. A power source is wired to the two conducting oxide layers, and a voltage drives the ions from the ion storage layer, through the ion conducting layer and into the electrochromic layer. This makes the glass opaque. By shutting off the voltage, the ions are driven out of the electrochromic layers and into the ion storage layer. When the ions leave the electrochromic layer, the window regains its transparency.


When switched off, an electrochromic window
remains transparent.





When switched on, a low volt of electricity makes the electrochromic window translucent.



With an electrochromic smart-window, it only requires electricity to make the initial change in opacity. Maintaining a particular shade does not require constant voltage. You merely need apply enough voltage to make the change, and then enough to reverse the change -- making this pretty energy efficient.

Although they can technically be classified as electrochromic materials, the new reflective hydrides that are being developed behave in a noticibly different way. Instead of absorbing light, they reflect it. Thin films made of nickel-magnesium alloy are able to switch back and forth from a transparent to a reflective state. The switch can be powered by low voltage electricity (electrochromic technology) or by the injection of hydrogen and oxygen gases (gas-chromic technology). Furthermore, this material has the potential to be even more energy efficient than other electrochromic materials.

Peter530i

Jstraw what a detail info

I love the mirror

JStraw

Well, Stoley did ask how they work

I generally like it, but wish there was a way to turn it off. There are times when the auto dim mirror hides a lot of detail when I'd like to see who is behind me (a cop for instance).

GB525dTour

Here's the scientific explanation (the discussion is about windows, but they explain how the technology applies to mirrors at the end):


Electrochromic windows darken when voltage is added and are transparent when voltage is taken away. Like suspended particle devices, electrochromic windows can be adjusted to allow varying levels of visibility. They are not an all or nothing technology like liquid crystals.
Electrochromic windows center around special materials that have electrochromic properties. "Electrochromic" describes materials that can change color when energized by an electrical current. Essentially, electricity kicks off a chemical reaction in this sort of material. This reaction (like any chemical reaction) changes the properties of the material. In this case, the reaction changes the way the material reflects and absorbs light. In some electrochromic materials, the change is between different colors. In electrochromic windows, the material changes between colored (reflecting light of some color) and transparent (not reflecting any light).

At its most basic level, an electrochromic window needs this sort of electrochromic material and an electrode system to change its chemical state from colored to transparent and back again. There are several different ways to do this, employing different materials and electrode systems.

Like other smart windows, electrochromic windows are made by sandwiching certain materials between two panes of glass. Here are the materials inside one basic electrochromic window system and the order you will find them in:


In this design, the chemical reaction at work is an oxidation reaction -- a reaction in which molecules in a compound lose an electron. Ions in the sandwiched electrochromic layer are what allow it to change from opaque to transparent. It's these ions that allow it to absorb light. A power source is wired to the two conducting oxide layers, and a voltage drives the ions from the ion storage layer, through the ion conducting layer and into the electrochromic layer. This makes the glass opaque. By shutting off the voltage, the ions are driven out of the electrochromic layers and into the ion storage layer. When the ions leave the electrochromic layer, the window regains its transparency.


When switched off, an electrochromic window
remains transparent.
Attachment 14411




When switched on, a low volt of electricity makes the electrochromic window translucent.
Attachment 14412


With an electrochromic smart-window, it only requires electricity to make the initial change in opacity. Maintaining a particular shade does not require constant voltage. You merely need apply enough voltage to make the change, and then enough to reverse the change -- making this pretty energy efficient.

Although they can technically be classified as electrochromic materials, the new reflective hydrides that are being developed behave in a noticibly different way. Instead of absorbing light, they reflect it. Thin films made of nickel-magnesium alloy are able to switch back and forth from a transparent to a reflective state. The switch can be powered by low voltage electricity (electrochromic technology) or by the injection of hydrogen and oxygen gases (gas-chromic technology). Furthermore, this material has the potential to be even more energy efficient than other electrochromic materials.
[/quote]

This forum rocks !

Rudy

You could just put your thumb over the rear-facing sensor for a few seconds to lighten the mirror, I guess...

JStraw, thanks for the details!

Mr 5er

However the hell it works, I love the mirror. I just love this technology.

stream

You could just put your thumb over the rear-facing sensor for a few seconds to lighten the mirror, I guess...

JStraw, thanks for the details!
[/quote]

I've had cars in the past that had an on/off button on the bottom of the mirror (and honestly never used it), but I'm happy to have a cleaner looking mirror--and as you say, you can always put your finger over the sensor on the top of the mirror.

Stoley

Thanks everyone!!! I enjoy researching all my car has to offer, and after almost 10 months, I never even knew the auto dimming mirrors were doing this!

Thanks!

E1142860

There is one negative aspect to the auto dimming rear mirror feature, at least for us. On our E28, when I'm driving during the day, I have the mirror set with the lever in the up or night position, as if I was driving at night and wanted to dim the mirror. Because my wife is 8" shorter than me, she merely needs to adjust the lever downward in the day position when she's driving in daylight for a perfect rear view position. This position is fine for me at night so it's like having a built-in memory position for the both of us. How come BMW has not incorporated memory positions for the rear view mirror a la the side mirrors?

evh5150

I have never found the auto dimming mirrors to be overly effective on most brands. Hope it works good on the 550!