Circuits designed by David Johnson,
P.E.
Last Updated on:
Monday, December 25, 2017 02:06 PM
Master Category List - Dave's Circuits
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Johnson, P. E. -- ALL Rights Reserved.
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More
LED
Circuits; Flasher Circuit |
Battery Free LED Flasher |
LED flashers have been used for a wide variety of applications. Some
flasher units have been used in food and hardware stores, to draw attention to
sale items and are often attached to boxes which dispense product discount
coupons. Typically, as the illustration below depicts, these simple units have a
red LED, on each side of the housing. Inside, is a battery and flasher
circuit. The housing also has space for rolls of preprinted sale coupons.
But, the batteries powering the flashing LEDs do have to be replaced every few
months. Since the flashing always occurs in well lit stores, there is
almost always enough natural and artificial light available to power a flashing
unit without using any batteries. Instead of batteries, a small solar
panel on top of the unit harvests enough energy to keep the unit flashing for as
long as light is available. A medium size super capacitor keeps the
available voltage hovering around 5.6v. This voltage allows the use of any
LED color desired. I like the super bright green LEDs myself. |
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Sales Coupon Flasher |
Sales Coupon Flasher |
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6v Solar Panel |
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Typical solar cells will produce
about 400ua of current per square inch of surface area in usual store fluorescent
light illumination. A 5.6v zener diode limits the voltage to the super
capacitor. |
The circuit below is designed to
flash two bright wide angle LEDs. Energy needed to flash the light is drawn
from the diffuse light available inside a commercial store. A six volt solar
panel on the top of the flasher assembly converts some of the light striking the
solar cells to electricity which charges up a super capacitor. The super
capacitor supplies the peak current needed to flash the two LEDs. A constant current
LED driver is used. The two LEDs are wired in parallel. Each receives about
10ma of current, lasting 20ms. The flash rate is once per second. The average
current is therefore about 400ua. |
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Click on Drawing Below to view PDF version of Schematic |
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Flasher Circuit
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