100 LEDs in Parallel

Wendy

Joined Mar 24, 2008
23,421
Lightweight, almost anything will do. I tend to use 2N2222A or PN2222A (the latter is a plastic case version of the first).
 

Thread Starter

vthokie11

Joined Jun 9, 2010
30
I wired up the circuit on a bread board but I'm having some difficulties...the LED lights fine but the pot and the CDS has no effect on it what so ever...I have attached a picture of the bread board and I would greatly appreciate it if you could look over it and see what I may have done wrong. Thanks.
 

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kubeek

Joined Sep 20, 2005
5,795
Does the led light when you short E-C?
If yes, does it light when you disconenct the potentiometer, and/or short the CDS?

With so few parts it can´t be that hard to find the fault.
 

Thread Starter

vthokie11

Joined Jun 9, 2010
30
Does the led light when you short E-C?
Yes.

If yes, does it light when you disconenct the potentiometer, and/or short the CDS?
Yes and Yes.

EDIT** The potentiometer does effect the LED but only when I turn the resistance way down...I don't have a multimeter on hand so I can't tell you at exactly what resistance this occurs.
 

cjdelphi

Joined Mar 26, 2009
272
if LED's in series if one of them blows, it will short right? and if it shorts what are the consequences ( a short in a series of LED's )
 

Thread Starter

vthokie11

Joined Jun 9, 2010
30
cjdelphi...I really have no idea...haha..I'm pretty new to this stuff

Just out of curiosity...could I use phototransistors as opposed to photo cells?
 

cjdelphi

Joined Mar 26, 2009
272
I used a Light Diode Resistor to do this type of circuit before, they're cheaper too but the photo transistor is faster and more responsive and obviously they can source current too without relying on a separate transistor the LDR would need (but i think the max rating is far below what you require you'd still need a meaty transistor to do the job).
 

Audioguru

Joined Dec 20, 2007
11,248
I have never seen a shorted LED because I never fry them with too much current.
If the current is correct then LEDs simply gradually dim. Then in about 10 years (continuously lighted) replace them.
 
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