G8MNY  > TECH     01.05.25 09:00z 51 Lines 2120 Bytes #46 (0) @ WW
BID : 31607_GB7CIP
Read: GUEST
Subj: Thermostatic Soldering Iron LED
Path: ED1ZAC<ED1ZAC<GB7CIP
Sent: 250501/0859Z @:GB7CIP.#32.GBR.EURO #:31607 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                 (Updated Mar 11)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

This circuit is suitable "Magnetic Curie Point" temperature switch controlled
mains irons! The LED lights up when the Iron is plugged in & is drawing current
in its heat cycle it goes out when it is up to temperature. It also works on
some internally electronic controlled 24V irons too.

Also shown is a static earth, that keeps the stray tip voltage down to about
12V AC MAX, while still giving an "un earthed iron" for work on live circuits
(~100V) safely.

CIRCUIT
  Fuse   ON
LÄo-oÄÄÄÄo\oÄÄÄÄÄÄÄÄ¿                        Temp
 250mA               )|| ÚÄÄÄÄÄÂÄÄÄoÄÄÄÄÄÄÄÄÄÄo_oÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
       LED           )||(     10k           Switch        Curie   ³
     ÚÄ´<ÃÄ¿     230V)||(24V ÚÄ´               :...Magnet Iron   12R Element
     ³     ³         )||(    ³10k                         Bit    48W
     ÃÄ´>ÃÄ´         )|| ÀÄÄÄ)ÄÁÄÄÄoÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
NÄÄÄÄ´     ÃÄÄÄÄÄÄÄÄÙ ³      ³-----------------------------iron earth
     ÀÄ33RÄÙ          ³     1M          If 3 wire
EÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÙ
   Á
The LED is connected to the mains neutral, but even so good insulation is
needed! The bypass diode connected the reverse way is a 1N4001 and stops mains
reverse voltage appearing across the LED. The value of 33R is selected so that
the LED is not lite with just the transformer magnetising current.

If the 50Hz flashing LED is anoying, blows up the LED, or is not bright enough
try this more complex circuit instead...

         LED
  ÚÄ´<ÃÂÄ´<ÃÄ´<ÃÄ¿
  ³    ³100u+³    ³      Here the 27R is selected for brightness & unlit LED
ÄÄ´    ÃÄÄ´ÃÄ´    ÃÄÄ    when the iron is not on. The 100uF protects the LED
  ô>ÃÄ)ÄÄÄÄÄÙ    ³      from some of spikes in mains power surges as well as
  ³    ÀÄÄÄÄÄÄ´>ÃÄ´      reducing the 100Hz LED flicker. Diodes are all 1N4001.
  ÀÄ27RÄÄÄÄÄÄÄÄÄÄÄÙ


Also see my Tech Bul on "Soldering Iron Economiser/Boost"


Why Don't U send an interesting bul?

73 De John, G8MNY @ GB7CIP


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