11 May
2010
11 May
'10
2:33 p.m.
On 11 May 2010 at 11:14, John Foust wrote:
> The four bulbs were identical as far as I could tell. Same
> flashlights, off the rack, as I said "I bought four $1 flashlights".
Getting back to the original problem, I don't believe that the fact that
a bulb came out of a torch that cost $1 uniquely specifies it :-)
I've not seen the original message (my ISP's mail is something of a joke
at the moment!) but as I understnad it, the OP had 4 similar filament
bulbs in series connected to a PSU and only one lit up. Some questions :
1) What is the voltageof thePSU compared to th nominal voltage of the
bulbs. If these are 3V bubls, is it s 3V PSU, a 12V PSU, or what?
2) Hat is the voltage across each bulb when they are wired in series and
turend ou?
3) What is th cold resistande of each bulb?
4) If you power each bulb individulally from a 3V (or whatever) supply,
what currents to they each draw?
5) If you have them in series an only one is lit, what happens if you
momentarily short out the lit bulb? Can you get the darn thing to have
several stable sttes?
Quite possibly Far East-origin flashlights? Put together from
whatever the local spot market makes available. BTW, the local
Harbor Freight "Chinese Tool Store" is giving away 9 LED flashlights
with spun aluminum housings (3 AAA batteries included), so these
bargain things can't come to much on the wholesale market.
We get those in some of the 'pound shops' over here. A good source of
white LEDs :-)
-tony