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G8MNY > TECH 17.01.09 10:07l 42 Lines 2019 Bytes #999 (0) @ WW
BID : 15398_GB7CIP
Read: GUEST DL9NDQ OE7FMI
Subj: Reducing Lamp surge
Path: DB0FHN<DB0FOR<DB0SIF<DB0MRW<DB0ERF<DB0FBB<DB0IUZ<DB0OVN<DB0GOS<DB0EEO<
DB0RES<DK0WUE<7M3TJZ<HG8LXL<XE1FH<ED1ZAC<GB7CIP
Sent: 090117/0012Z @:GB7CIP.#32.GBR.EU #:15398 [Caterham] $:15398_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (New Jan 09)
(8 Bit ASCII Graphics use code page 437 or 850)
On an Over Head Projector I have used this surge limiter to greatly reduce the
chance of lamp failure at turn on. This circuit is suitable for most low
voltage lamp systems.
high current
relay contact VOLTS COLOUR
\ 24 ¿ _..--ÄÚ White
ÄÄÄÄÄÄÄÂÄÄÄß ÀÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÄ¿ 21 ´ Ý ³
³ ³ ³ ³ 20 ´ Þ Ã Yellow
Lamp ³___1R5__³ Rstart ³ 18 ´ .úÙRelay ³
Supply 50W _³_ ³ 15 ´ . Operates à Orange
\_/ LAMP 12 ´ . ³
e.g. ÚÄÄÄÄÄÄÄ´ ³ 9 ´ / ³
24V +³ ÚÄÄÄÄÁÄÄÄÄ¿ ³ 6 ´ .' Ã Red
@ 11A 100u === ³12V Relay³ ³ 3 ´.ú' ³
16V ³ ÀÄÄÄÄÂÄÄÄÄÙ ³ 0 ÅÄÄÄÂÄÄÄÂÄÄÄÂÄÄÄÂÄÄÁÄ>TIME
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÙ 0 1 2 SECONDS
The delay time is really nothing to do with R Start & the 100uF, but the lamp
temperature, that determines the lamp resistance & hence the voltage drop
across the surge limiting 50W R. This means the turn on delay is reduced if the
lamp is already hot.
The 1R5 is made from several wire wound resistors to give the short term power
dissipation. The value is chosen to let the lamp get to a good orange to
yellow colour temperature before the relay applies full power. Care must be
taken for the location of this resistor & near any fanned air flow is useful.
The value of Rstart determines the operating voltage for the relay it may need
to be a power resistor if the relay id not sensitive.
The 100uF Cap stops the relay humming @ 50Hz by smoothing the applied voltage.
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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