Article

Slave Flash for Digital Cameras

Don’t throw away your old flashlight!

Although most digital cameras have a built-in flash, a connection for an external flashlight is rarely seen. Still, on some occasions it’s useful to have just a tad more light and that’s why we propose a simple add-on.As many of you will be able to avow, the light capacity of the flash facility on low-cost digital cameras is often marginal if not insufficient. Problems typically occur where the object to be photographed is too far away, or if a (very) short shutter time is required. In those difficult cases, the slave flash we’re about to describe may come in really useful.The idea is simple: detect the flash from the camera and use it to trigger a powerful external flashlight with the aid of a thyristor.

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Materials

040224-PCB.pdf

Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

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PCB

Download Gerber file: 040224-1.zip

Extra info / Update

The parts list should be corrected to readR1 = 3k3R11 = 68kT4 = BC556

Component list

Resistors:
R1 = 27kOhm
R2 = 390kOhm
R3 = 56kOhm
R4,R5 = 10kOhm
R6 = 1kOhm
R7 = 2kOhm 7
R8 = 2kOhm 2
R9,R10 = 470kOhm
R11 = 180kOhm
R12 = 4MOhm 7
R13 = 1MOhm
P1 = 250kOhm preset
Capacitors:
C1,C6 = 100nF
C2 = 1nF
C3 = 220nF
C4 = 1µ F 16V
C5 = 2nF2
Semiconductors:
D1,D3 = 1N4148
D2 = LED, 3 mm, low current
T1 = BPW40
T2,T3 = BC547
T4 = BC557
Th1 = TIC106
IC1 = 4017
IC2 = SFH601
Miscellaneous:
Bt1 = 9-V battery with clip-on lead
S1 = pushbutton with 1 make contact
K1 = 20-way boxheader with jumper, or a double-row pinheader (2 x 9) with jumper
PCB, available from The PCBShop, ref. 040224.