Things you always wanted to know the answer to [Vol. 3]

[Rebew]

How do rain sensing wipers on cars work? How do they know that the screen is wet?

[Bluedot]

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

[jet_noise]

Bluedot said:

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

But what does the sensor sense?
Light, dear Lisa, light.
Water on the screen changes the reflective properties of the glass surface. Sensor fires infrared at it and measures how much is returned,

regards,
Jet

[MartG]

jet_noise said:

Bluedot said:

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

But what does the sensor sense?
Light, dear Lisa, light.
Water on the screen changes the reflective properties of the glass surface. Sensor fires infrared at it and measures how much is returned,

regards,
Jet

Are you sure they aren't resistance or capacitance sensors ?

[Rostfritt]

a said:

Camera film was very insensitive to light back then - so you needed a lot of light and a long exposure time. Not a problem for landscape photos, but quite difficult for live subjects. Any motion at all would result in blur.

I can't remember exactly - but I believe a typical exposure would last over a minute in the 1800s. That's why many of the subjects are sitting or at least standing in a sturdy/upright position to minimise movement. And it's hard to hold a perfect smile for that long - so a blank stare was required.

Nobody in the 1870s was ever happy about anything for a whole 30 seconds.

[Rostfritt]

gazzarose said:

Isn't there something about only 1 species of frog makes the 'reddit' sound, and coincidentally it lives in the hills around Hollywood. It's been used as a stock frog sound in films since the 30s or something.

Possibly. On a similar note, on films when someone is on a landline and the other caller hangs up, they get a dial tone. This is not normal as you usually get silence. This is because for some peculiar reason, the phone provider around the Hollywood area gave you a dial tone, so everyone assumed that was normal.

That or it just makes a good audible indication when someone is hung up on.

[227bhp]

Funkycoldribena said:

227bhp said:

Funkycoldribena said:

What era did people start picking up their dog poo?
Were Victorian seafronts minefields?

I'm guessing you're about 12?

I wish.
What's so childish about it? Just curious.

I was referring to the fact it's very recent, it must be less than 10yrs ago when we started bagging it.

RE: The Victorians, I don't think it was as popular back then to keep a pet dog, the working class couldn't afford to feed another mouth.

[MartG]

Rostfritt said:

gazzarose said:

Isn't there something about only 1 species of frog makes the 'reddit' sound, and coincidentally it lives in the hills around Hollywood. It's been used as a stock frog sound in films since the 30s or something.

Possibly. On a similar note, on films when someone is on a landline and the other caller hangs up, they get a dial tone. This is not normal as you usually get silence. This is because for some peculiar reason, the phone provider around the Hollywood area gave you a dial tone, so everyone assumed that was normal.

That or it just makes a good audible indication when someone is hung up on.

In the UK I think it depends on who originates the call - if the person who dialled hangs up then the connection is cleared and the recipient will get the dial tone. If the recipient hangs up the circuit isn't cleared so the caller doesn't get a dial tone - and if the recipient picks the phone up again the caller will still be there. This is often used by scammer to trick people into thinking they are talking to a bank or something

[Bluedot]

jet_noise said:

Bluedot said:

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

But what does the sensor sense?
Light, dear Lisa, light.
Water on the screen changes the reflective properties of the glass surface. Sensor fires infrared at it and measures how much is returned,

But why then would the guy replacing the windscreen lick his finger, surely just putting his finger over the sensor would change the light going to it ?

[MartG]

Bluedot said:

jet_noise said:

Bluedot said:

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

But what does the sensor sense?
Light, dear Lisa, light.
Water on the screen changes the reflective properties of the glass surface. Sensor fires infrared at it and measures how much is returned,

But why then would the guy replacing the windscreen lick his finger, surely just putting his finger over the sensor would change the light going to it ?

See my post above - I think they work on resistance or capacitance

[wiggy001]

Why are tea bags sold in multiples of 40? And is any other product sold in 40s?

[Rebew]

MartG said:

Bluedot said:

jet_noise said:

Bluedot said:

Rebew said:

How do rain sensing wipers on cars work? How do they know that the screen is wet?

On mine there is a little sensor at the top of the screen (think it might even be built in?).
When my windscreen had to be replaced, afterwards, the guy licked the end of his finger and put it on the sensor to check they worked ok!

But what does the sensor sense?
Light, dear Lisa, light.
Water on the screen changes the reflective properties of the glass surface. Sensor fires infrared at it and measures how much is returned,

But why then would the guy replacing the windscreen lick his finger, surely just putting his finger over the sensor would change the light going to it ?

See my post above - I think they work on resistance or capacitance

This is my problem, I know my car has sensors behind the rear view mirror but I thought that was for headlights, how would that sensor know when water lands on the bottom of the screen? It's got to be resistance or magic?

[mart 63]

Why do flies circle in the dead centre of a room?

[djc206]

wiggy001 said:

Why are tea bags sold in multiples of 40? And is any other product sold in 40s?

I think you get about ten servings per ounce of loose tea so 40 bags is a quarter. 160 being a lb. Happy to be corrected.

[227bhp]

mart 63 said:

Why do flies circle in the dead centre of a room?

Around the light fitting maybe?

[Ayahuasca]

227bhp said:

mart 63 said:

Why do flies circle in the dead centre of a room?

Around the light fitting maybe?

Coriolis effect, in the southern hemisphere they fly the other way around.

[Rostfritt]

Rebew said:

This is my problem, I know my car has sensors behind the rear view mirror but I thought that was for headlights, how would that sensor know when water lands on the bottom of the screen? It's got to be resistance or magic?

Surely the sensor needs to be in the sweep of the wipers? Otherwise they would go forever if a drop landed on them.

As a prank you could put a drop of glue or something on the sensor and their wipers wouldn't stop.

[dudleybloke]

mart 63 said:

Why do flies circle in the dead centre of a room?

Because that's where the carpet fitter took a dump before laying the carpet.

[john2443]

Ayahuasca said:

227bhp said:

mart 63 said:

Why do flies circle in the dead centre of a room?

Around the light fitting maybe?

Coriolis effect, in the southern hemisphere they fly the other way around.

So do flies on the equator fly straight ahead and crash into the walls

[john2443]

227bhp said:

I was referring to the fact it's very recent, it must be less than 10yrs ago when we started bagging it.

Longer ago than that. I was in a park in Trowbridge or Bradford-O-A in about 1991/2 (I remember because of who I was with, how old kids were and that we'd spent the afternoon rebuilding a gearbox!) and park ranger type person was giving out poo bags, I guess that was the early days of bagging it and they were encouraging people to do it.