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old dick smith catalog mains led circuit?

niftynev

Mar 20, 2010
22
Joined
Mar 20, 2010
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22
hi everyone! my first post (for quite a while! lol!).

i obviously haven't still got an old enough tricky dicky catalog! in the data section there used to be a circuit to run an led off the mains (240vAC). the circuit is not in the later catalogs.

i built 2 of them years ago into a power point for my mom. they worked well for years, but she's got new outlets now so i can't copy the circuit from them.

i seem to remember a series connected 470nf (mains rated) cap & a couple of hundred k resistor with the led. i think the led also had a diode connected across it in the reverse direction to the led.

being the mains, & a safety issue, i didn't want to have to redesign the wheel, but use a time-tested circuit.

i've been given a hundred or more 100nf 275V X2 caps plus a heap of 150 degree wide beam smd white leds, & my intention is to re-use an old cfl lamp base, with a few of these leds mounted in place of the fluoro tube. i've disposed of the cheap crappy inverter pcb, so reusing that piece of junk quality electronics is out of the question.

i'll probly have to parallel up caps which is ok (i got heaps!:)). i'll just have to make sure they'll fit inside the old fitting! the space inside it will dictate how many leds i can run this way.

thanks in advance!
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
You can do it with a capacitor, a resistor, and another diode.

The problem is that the entire circuit operates at mains potential.

I really don't recommend it -- and mainly due to the mains wiring...
 

niftynev

Mar 20, 2010
22
Joined
Mar 20, 2010
Messages
22
thanks Harald!

not the dick smith catalog circuit, but pretty close.

but on the next page after the one you showed me was a MUCH better one, with 15 leds!

all the 'gubbins' for it is EASILY gunna fit inside an old cfl fitting!

perfect!

THAT'S the one i'm gonna try!

i'll let youse know how i go.

p.s. yeah steve, you're SO right! we must be super careful with this kinda wiring. i will be i promise. i build/repair 7kV power supplies every other day so i know the dangers!

cheers nn
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
If you're not going to put a fuse in series with this circuit, I would advise placing a low value resistor in series with the capacitor. This will act like a fuse if the capacitor goes short circuit.
 
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