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Low-Power LED Flash

powered bylemon juice

Low-Power LED Flash
This circuit will need just a few micro-amps to make an LED flash. The energy comes from a home made ‘vegetarian’ battery.We have to admit that the circuit shown in Figure 1 appears a bit over the top for an on/off indicator, as the same functionality could have been achieved from a classic combination of an LED and a series resistor. However, the circuit is unbeaten we feel in that it shows how a visual on/off indication may be realised in battery-powered equipment, while using a minimum of energy.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

R1,R6 = 1MOhm
R2 = 3MOhm3
R3,R4 = 9MOhm1
R5 = 100kOhm
C1,C2 = 1µ F 16V (see text)
D1 = LED, red, low current
IC1 = TS271C (see text)
T1 = BC557C
T2 = BC547C
K1 = 2 solder pins
2 solder tags
9 copper or coppered discs (e.g. coins, see text)
9 aluminium discs (see text)
Absorbing kitchenpaper (see text)
1 lemon (or pure lemon juice, see text)
1 rubber ring
PCB, available from The PCBShop
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