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Volthaus Electronics Laboratory made it! (author)2014-08-11

Great Instructable. I have one question. Since you're showing a positive
voltage to the base of the transistor it appears your schematic is
calling for a NPN transistor. In that case the negative lead of the LED
needs to go to the collector on the transistor rather than the emitter
as shown. Using a PNP transistor the emitter is the negative side but so
is the base. From the book Make: More Electronics by Charles Platt -
Transistors will work to some extent when reversed, although some
degradation may occur. You can use it the wrong way around and get some
results from a circuit, although not quite what you expect. If you then
discover your error and reverse it quite probably you still won’t get
the results you expect, because the transistor has been damaged by
reversed polarity. I made mine running the negative lead of the LED to the
collector on a NPN3904 and it worked perfectly. Thanks.

Ploopy (author)2013-07-17

I made my version of this ible

hope you like it

Ploopy (author)2013-07-13

Made one!

Ploopy (author)2013-07-09

Why do you need a resistor for the led if you're using 3v?

mariollop (author)2011-02-17

does it matter if its a pnp or a snp transistor?, i did the hook up w/ supply voltage 2 aa batt. 1.5 each and does the size of the eldr matter?

__DELETED__ (author)mariollop2011-02-17

I haven't heard of an snp transistor....

As far as I know the size doesn't matter, but the one I used was about 4x5mm

mariollop (author)__DELETED__2011-02-18

thanks for the response , i meant npn .

__DELETED__ (author)mariollop2011-02-19

I don't honestly know the difference between the two.

Sorry for being useless >.<
I'm just a beginner in electronics really...

Thanks for checking out my 'ible though :-)

ledfreak01 (author)__DELETED__2013-02-18

an npn transistor means it needs a positive volt to turn on and a pnp transistor needs a negative volt

ledfreak01 (author)ledfreak012013-02-18

and in this aplication i beleive you need a npn transistor

keithosmarferrer (author)2011-05-22

i have a quick question, can i change the LED into a motor?

I don't see why not... You would need to use a battery strong enough

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