Article
Low-Power LED Flash
powered bylemon juice
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.
Materials
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.
Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
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PCB
Component list
Resistors:
R1,R6 = 1MOhm
R2 = 3MOhm3
R3,R4 = 9MOhm1
R5 = 100kOhm
Capacitors:
C1,C2 = 1µ F 16V (see text)
Semiconductors:
D1 = LED, red, low current
IC1 = TS271C (see text)
T1 = BC557C
T2 = BC547C
Miscellaneous:
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
R1,R6 = 1MOhm
R2 = 3MOhm3
R3,R4 = 9MOhm1
R5 = 100kOhm
Capacitors:
C1,C2 = 1µ F 16V (see text)
Semiconductors:
D1 = LED, red, low current
IC1 = TS271C (see text)
T1 = BC557C
T2 = BC547C
Miscellaneous:
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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