LED flasher

Hi All,
Im looking for a simple LED flasher circuit that will accept a 9v supply
(battery) and has a run time of ~8 weeks. I have found a few IC based
circuits but I was looking to go even simpler so I can do away with a board
altogether.
Cheers
Wayno

 

Any number of led's with the flasher circuitry built in. Go to Jaycar here.

http://www1.jaycar.com.au

 

If you want the simplist solution available, use a flashing LED. The
flash circuit is built into the LED.
Are you stuck with using a 9V battery? If you want really long life, a
single D cell is a good way to go. You can get single or dual cell LED
flasher chips. 9V batteries have poor energy density and are more
expensive.

Regards
Dave

 

How long do you want the LED lit verses off? How bright? What colour?
There isn't much energy density stored in a 9 volt battery. 8 weeks is
a LONG time!

A single CMOS 555 chip connected as an oscillator with the LED in
series with the discharge lead would probably be the most energy
efficient. I would also recommend that you consider 6 or even 4.5
volts as a power source (3 X D cell). A red high efficiency LED is a
current device that only requires a low voltage to operate and
probably will give you the brightest flash with the smallest amount of
current drain to get you near the 8 weeks operation on one set of
batteries. Besides the 8 pin chip, all you need is a couple of
resistors and a capacitor. This could easily be wired point to point
on a piece breadboard.

A couple of more details would be helpful. What's it for?

I purchased flashing LED modules for my kids to wear when they are
riding their bicycles. I found them at a discount store for 99 cents
each, the regular price was 8.99. They operate on a two AA cell and
allow you to select 1 of 3 different flashing "modes". In the early
spring and late fall, they go to Canoe/Kayak practise early in the
morning (5AM) and wear these on the river so they don't get hit by
rowers practising. Batteries last about 2 weeks worth of practises-
guessing about 16-25 hours of actual operation. Be aware that some of
these units use very expensive button style batteries with limited
operational life. If you go this route, choose carefully.

Cheers from Canada

Bob M

 

** An Energiser 9 volt battery has 625 mAh with an average voltage of 7.2
volts = 4.5 Wh.

An Energiser D cell has 18 Ah with an average voltage of 1 .1 volts =
19.8 Wh.

Allowing for the size difference (17.0 cc versus 58 cc ) the 9 volt
battery is not too bad at 0.26 Wh/cc compared to 0.34 Wh/cc.



............ Phil