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G8MNY > TECH 24.07.12 23:17l 44 Lines 2170 Bytes #999 (0) @ WW
BID : 52322_GB7CIP
Read: GUEST
Subj: LED as a mains NEON
Path: IZ3LSV<IK2XDE<ON4HU<F6IQF<IK6ZDE<I0OJJ<GB7CIP
Sent: 120724/2132Z @:GB7CIP.#32.GBR.EU #:52322 [Caterham Surrey GBR] $:52322_GB
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Update Dec 05)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Neon lamps that run too brightly usually don't last long as the glass blackens
with electrode metal. To replace the neon does not cost much if you have a
source of them. But to replace the whole thing for an LED with a bridge
rectifier & a suitable mains capacitor & surge R is far more expensive..
ORIGINAL SIMPLE REPLACEMENT BETTER COMPLEX REPLACEMENT
1mA 20mA 10mA u15 10mA
LÄÄ180kÄÄÄÄ¿ ÄÄ12kÄÄÂÄÄÄ¿ Ä12kÄ´>ÃÂÄÄÄ¿ ÄÄ1kÄÄÄ´ÃÄÄÄÄÂÄÄÄÄÄÄÄÄÄ¿
1/4W ,-³-, 5W ³ ³ 3W ³ ³ 1/4W (X=20k)_³_ _³_
/ ÄÁÄ \ _³_ _³_ _³_ _³_ (@50Hz) /_\ LED \_/
80V | o | LED <-\_/ /_\ <-\_/ /_\ ÃÄÄÄ´<ÃÄÄÄ´
NEON \ ÄÂÄ / 1.5V <- ³ ³ ³ ³ _³_ 10mA _³_
`-³-' 10mA³ ³ 10mA ³ ³ \_/ /_\
NÄÄÄÄÄÄÄÄÄÄÙ ÄÄÄÄÄÄÄÁÄÄÄÙ ÄÄÄÄÄÄÄÄÁÄÄÄÙ ÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ
Power = 0.24 W 4.8 W 2.4W 0.4 W
Flicker = 100Hz 50Hz 50Hz 100Hz
The Neon has 80V drop & to give reasonable brightness, 1mA is needed. Whereas
the LED needs say 10mA @ 1.5V drop for the same sort of brightness as it is far
more directional light source.
With just a reverse protection diode & a R, the R needs to be many watts (5W)!
50Hz flicker.
Adding a high voltage series diode in the arrangement halves the power, but
will add DC component to the supply & also it may cause more QRM. 50Hz flicker.
Using a mains AC capacitor as the current dropper, due to it's impedance makes
for a more efficient if complex arrangement, but still a spike current limiting
R is needed as well. Using a bridge rectifier also doubles the current into the
LED, making it more efficient. The C needs to be about 0.15uF @250V AC with a
surge R (fuse type) of say 1k. 100Hz flicker.
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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