For a Dollar

[UnknownVT]

Look what I got for a dollar at a local Dollar Tree store -

Yes, it's an auto-scan FM radio with earbud headphones.

But what caught my eye was the little nub/protrusion near the top...

That looked like a LED to me - so was it a flashlight too?

Looking at the package - it was:

Getting it home I couldn't wait to put 2x AAA batteries in it and try it out - that's the flashlight part....

The beam looked quite good and it surprised me it wasn't the cool blue white of a typical white LED - so have I discovered a warm white LED?

No such luck - the beam was on further consideration more yellowish - that I eventually realized it could not be a LED.

I opened up the gadget and the light "bulb" still looked more "solid state" than a normal incandescent light bulb, even if it wasn't the regular 5mm LED shape.

Even on close examination the bulb still looked like a solid piece - but the "element" did not look like a LED emitter.

Here's an extreme close up of the bulb -
it is incandescent as far as I can tell - but it almost looks solid -

The radio?

It's not that great on the supplied earbuds - using much better quality earbud headphones does not improve things that much - reception is actually pretty good - but music is distorted mostly - speech is kind of OK.

I saw 4 different designs - they were all FM auto-scan radios - but only 2 designs were also flashlights......

Hey for a buck it's not a bad buy......

 

[paulr]

I have one of those that I paid $2 for. I thought it was an led too. If I can find it I'll take a closer look. An incan actually makes more sense than a white led, since I doubt there's a boost converter in that 2aaa radio to run the led with. A yellow or red led might be another possibility.

 

[MaxaBaker]

Not bad for a dollar /ubbthreads/images/graemlins/smile.gif

 

[UnknownVT]

[ QUOTE ]
paulr said: I thought it was an led too.

[/ QUOTE ]

I can only see it on that extreme close up - the bulb appears to be on two solid looking parts - the upper dome and lower base - sandwiching what looks kind of like a tube for the element.....

One can just see the element and dome are at an angle - so my light points to the right even when the bulb is aligned straight forward.....

Another interesting oberservation is that there is no stray extraneous side emissions like the side "spikes" typical of 5mm LEDs - even though this bulb seems to have a solid dome too. Perhaps it's because the element is not as close to a point source as on an LED? There's a dark center to the beam. and when held close to a wall I think I'm seeing the shadow of the element shape?


Typical side "spike" emissions of a 5mm domed LED

ref:
Stray Side Emissions of Domed LEDs

 

[paulr]

Is the envelope glass or plastic?

 

[wquiles]

Cool photo of the LED on the degree scale /ubbthreads/images/graemlins/grin.gif

 

[UnknownVT]

[ QUOTE ]
paulr said:
Is the envelope glass or plastic?

[/ QUOTE ]

Can't tell for sure Paul -

I think it looks and feels like glass -
but then I'm probably influenced by the fact I think it is an incandescent and can't see how it could be plastic....

Sorry not a good answer - but the best I could do.

 

[Lynx_Arc]

It is an incan bulb. I can see the filament and the two wires supporting it. The cell phone charger I got for 1.00 also had a similar incan bulb in it. The clue for incans is easy. just put a resistor inline with it and dial in resistance and if it turns yellow, then orange, then red then it is out.... it isn't LED.

 

[PhotonWrangler]

I agree. The filament, support wires and the insulating glass bead are clearly visible. I think what makes it look unusual is the glass "base" at the bottom as well as the molded-in lens at the top. Sometimes called a prefocused bulb.

Not bad for a buck though! /ubbthreads/images/graemlins/grin.gif

 

[mossyoak]

never thought of using a protractor that way i might have to start using one of those

 

[Big_Ed]

Another way to tell if it's LED or incan is to turn it on for a minute or so and see if it gets hot. If it does, it's an incan, if not, it's an LED.

 

[UnknownVT]

[ QUOTE ]
wquiles said:
Cool photo of the LED on the degree scale /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

[ QUOTE ]
mossyoak said:
never thought of using a protractor that way i might have to start using one of those

[/ QUOTE ]

Many thanks for the kind comments -

I started to use what I jokingly call "JugShots" to show the beam coverage profile.

Here's the thread over on the LED forum -

Light Coverage - spill-diameter Pics

It's a JugShot - literally because I use a frosted plastic water/juice jug -

Follow the thread and one can see that sometimes there may be some difficulty aligning the protractor accurately.

 

[cobb]

I must of missed that, although since I have satelltie radio, I have lost all interest in fm/am radio.

I saw one clip on radio that was auto scan that uses two coin button batteries.