On 08/01/2020 18:58, Dave Plowman (News) wrote:
In article ,
Steve Walker wrote:
On 08/01/2020 17:05, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
cheap chinese motors used in e.g. car window winders are deliberately
pants to that they can be stalled without burning out wires or fuses.

Car window winders are an especially bad example. They use load sensors
to ensure nothing is trapped, such as a child's arm, in the window.

Interesting. Never come across that. How do they work? And why fit a motor
so powerful it could do an arm damage? Most are easily stopped by hand.

An arm is not a problem, a neck is. It takes very little pressure to
stop either breathing or cut off blood to the brain. Children have died
that way, which is why load sensors were added.

When were load sensors added? Given electric windows have been around for
a long long time, if not so long on UK cars.

Back in the early '90s I think.

A reasonably powerful motor is required, because otherwise you could be
unable to open it (or worse, close it) as the car ages and the mechanism
stiffens or when there is ice on the doors. A 90's Cavalier used to have
an override button on the centre console to temporarily disable the load
sensors for this. These days repressing the button a few times does the
same for some vehicles.

So how does the motor know if it is friction or ice or whatever rather
than a child's neck?

Like I said, at least one of the early overrides was by a separate
button, but later repeated pressing would do it. The system doesn't know
what's in the way, but it does know that you have realised that the load
sensor has stopped the window and you have taken further action to
override it.

It is likely that the reason that you can easily stop a window, is
because it is sensing too much load and stopping - some actually reverse
a short distance as well.

Early Rolls Royce windows stopped just short of closed. You had to press a
second button to close it fully. To avoid trapped fingers. That was so
inconvenient it was discontinued.

Yes. I can see that would be an annoyance.

SteveW