Faucet light

[kt315]

I came across one of these on the ebay: http://www.ebay.ca/itm/230867280850?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648#ht_3115wt_1378

Any ideas how it is powered?

[IanB]

It says "no batteries required" so it probably uses a small turbine that spins as the water flows. It only needs to generate a few mA to power an LED.

[FenderBender]

That's pretty good for US $3...

[David_AVD]

I bought one to see how it worked.  There is a battery - the packaging lied.   

Basically a pair of button cells, an LED and a (water) pressure switch.

[c4757p]

I bought one to see how it worked.  There is a battery - the packaging lied.   

Shocker.

[FenderBender]

I figured as much. Not that a little dc motor and a turbine and some diodes costs that much, but for $3 idk bout that.

[DavidDLC]

And seems like it has a temperature sensor, since the color changes based on the water temperature.

David.

[David_AVD]

I don't recall if the one I got was colour changing (with water temperature) to be honest.  It could have been, but I do recall the coin cells.

[IanB]

I bought one to see how it worked.  There is a battery - the packaging lied.   

Basically a pair of button cells, an LED and a (water) pressure switch.

Ah, makes sense. A bit like those (fake) magnetic "shake to operate" torches then, that also have a coin cell inside them...

[FenderBender]

Wait no I thought he meant, just a switch that turns it on, not powering it.

[IanB]

Wait no I thought he meant, just a switch that turns it on, not powering it.

Yeah, I know. They used to sell those torches that pretended to have a generator inside them, but all along they just had a battery and a switch that activated when you would shake them. All seemed fine for a year, until the battery expired and they stopped working.

[David_AVD]

You mean somebody was making and selling something that was a sham?  Say it ain't so!   

[kt315]

Yeah, I was wondering where does it actually take power from. But I guess the phrase "does not require battery" can be a bit misleading. 

[Jon Chandler]

I got one of these and it is powered by a turbine.  You can hear the buzz as it turns.

It has three colors, rather bizarrely arranged.  Cold water results in green light, warm water in blue and hot in red.  It does take a second or two to change with temperature.  Seems kind of gimacky, but it quickly becomes natural to check the colors before washing hands with cold water or getting a scald with too hot of water.

[David_AVD]

There must be different varieties of them.  I think I got mine from an AliExpress seller.

[Hydrawerk]

Ah, makes sense. A bit like those (fake) magnetic "shake to operate" torches then, that also have a coin cell inside them...

Esactly. I got one in about 2002 and it was crap. In 2003 I got this rotating mobile phone charger with a white LED. It's been produced for a long time. I put a 1 Farad 5V capacitor there. This is now my real hand powered torch.

[daveshah]

I once had a 'solar powered' torch that had a solar panel and diode (to prevent the battery from discharging through the panel) connected in parallel with an ordinary non-rechargeable CR2032. When I took it apart, the battery had an open circuit voltage over 5V! It dropped to almost nothing under load though.

[M0BSW]

I bought one to see how it worked.  There is a battery - the packaging lied.   

Basically a pair of button cells, an LED and a (water) pressure switch.

They Lied, surely not, advertisers don't lie do they.

[amyk]

This is something I'd like to see a teardown of (one with generator preferable, but "fake" one would be fine too.)