Article

LEDify It!, mobile 3-watt LED Lamp

A traditional hand-held torch could hardly be described as a cutting-edge piece of technology; in fact it's probably the exact opposite, circuits don’t come much simpler! Text books have for years used a battery, light bulb and switch to describe just what a circuit is. We are also aware of the shortcomings of the filament lamp; the light dims as the battery discharges and occasionally you need to replace a burned-out bulb. Why not treat an old torch to a 21st century make-over? Replace the bulb with more efficient LEDs, the 5 mm 70 mW types will not be very illuminating but 1-watt white LEDs are now reasonably priced.
It’s not quite as simple as removing the bulb and replacing it with an LED.

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Materials

080585-PCB.pdf

Gerber file

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PCB

Download Gerber file: 080585-1-V20

Extra info / Update

Features

* Three 1 W LEDs powered from 4.8 V
* Efficiency > 80 %
* Light output independent of battery voltage
* Battery deep-discharge protection

Component list

Resistors
R1,R3 = 2kO2
R2 = 22k
R4,R5,R6 = 1k
R7,R9 = 100k
R8 = 3MO9
R10 = 4kO7
R11 = 560
R12,R13,R14,R15 = 1
P1,P2 = 10kO preset, miniature, horizontal
P3 = 5kO preset, miniature, horizontal
Capacitors
C1 = 330nF MKT lead pitch 5mm or 7.5mm
C2 = 47µF 25V radial, lead pitch 2.5mm, ø max. 8.5mm
C3,C4,C9 = 100nF ceramic, lead pitch 5mm
C5,C6 = 470µF 16V radial, lead pitch 2.5mm, ø max. 8.5 mm
C7 = 10µF 63V radial, lead pitch 2.5mm, ø max. 6.5 mm
C8 = 100pF ceramic, lead pitch 5mm
Inductor
L1 = 100µH axial, upright mounting, suggested types: 5800-101 (Bourns) rated 0.63A/0.2O (Digi-Key # M8290-ND), B82111EC25 (Epcos) rated at 1A/0.65O (Farnell # 9752102) or MESC-101 (Fastron) rated at 1A/0.65 O (Reichelt # MESC 100µ)
Semiconductors
D1 = 1N5822
D2 = 2V7 0W5 zener diode
D3 = 1N4148
T1 = BD139
IC1 = LM2577T-ADJ (TO-220-5 case, straight pins)
IC2 = LM358 (DIP-8)
Miscellaneous
K1,S1,BT1 = 2-way PCB terminal block, lead pitch 5mm
S1 = single-pole on/off switch
BT1 = holder for 4 NiMH batteries*
3 pcs 1-watt power LED
PCB # 080585-1
* see text