Slave Flash with Red-Eye Delay

Digital cameras are becoming more and more affordable. At the economy end of the market cameras are usually equipped with a small built-in flash unit that is ideal for close-ups and simple portraiture. The power rating of the built-in flash unit is quite low so that any subject further away than about 2 to 3 metres (maybe 4 m if you are lucky) tends to disappear into the gloom. You soon become aware of the limitations if you need to photograph a larger group of people say at a function under artificial light in a large hall or outdoors. The majority of these cameras are not fitted with an accessory socket so it is not possible to simply connect a second flash unit to increase the amount of light.

Resistors:

R1, R3 = 100k

R2 = 100Ω

R4, R5 = 220k

R6 = 1k

Capacitors:

C1, C3 = 10µF 16 V radial

C2, C4 = 100nF

C5 = 47nF

Semiconductors:

D1 = TLRH180P (Farnell # 352-5451)

D2, D3 = BAT85

IC1 = 4538P

IC2 = MOC3020

T1 = BC547B

Miscellaneous:

Bt1 = two 1.5V batteries (LR44) with PCB mount holder

S1 = 3-position slide switch 

PCB, ref. 040070-1 from The PCBShop

Cable or adaptor for external flasher