can a 1.5 button battery be used in a normal 1.5v LED flasher project
i need to make a small LED flasher and i've read many 1.5v project. is it possible to use a button battery? is there any circuit diagram that i can use? emergency.. i need it fast
You could use a button battery, as long as it's able to supply enough current?, but bear in mind it won't last very long, they only have a very small capacity. Google for "joule thief" for circuits.
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk
There is no such thing as a "1.5V " LED. It might be 1.3V and burn out with a 1.5V supply or it might be 1.8V and not light with a 1.5V supply.
LEDs are driven with current, not voltage. Usually a current-limiting resistor is in series with an LED (or the internal resistance of a tiny battery) and the supply voltage is higher than the LED's max voltage rating.
I sketched the voltage stepup circuit for my solar garden light and added a flashing circuit to it. It will work with a 1.5V LED or a 3.5V LED when the battery voltage is less than 1.0V.
EDIT: Added a transistor to isolate the voltage stepup circuit from the flasher circuit and to make the LED blink briefly instead of pause briefly.
Last edited by audioguru; 20th October 2007 at 07:06 PM.
Uncle $crooge
This is a great example that current drives a LED, not voltage:
http://www.youtube.com/watch?v=roPJosBqsXA
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Most LED projects use 3x of the 1.5v button batts because 1.5v isn't enough to light common LEDs. 2x (3v) can light red ones but there's not much headroom voltage for a ballast resistor to stabilize the current.
The 3V lithium "coin" batteries get used a lot without resistors in flashlights, because the battery's output resistance is itself high enough to limit the LED current.
Last edited by Oznog; 21st October 2007 at 12:24 AM.
I thought what I'd do was I'd pretend I was one of those deaf-mutes.
That is why they are also in computers as backup memory, since it has high enough ESR.
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? A backup memory has no use for a high ESR. Very few apps actually desire a high ISR, the tiny LED flashlight thing is a very unusual case.Originally Posted by Krumlink
Lithium coins are good for holding backup memory because the app can tolerate high ESR batts ok.
I thought what I'd do was I'd pretend I was one of those deaf-mutes.
The main reason Lithium batteries are used for memory backup is their extremely low self discharge rate. Since the CMOS memory chips draw next to nothing while in standby, it is really the "shelf life" of the battery that determines how long it will last in this application.
Inside every little problem, is a big problem trying to get out.
Too bad the old LM3909 isn't made anymore. Radio Shack used to sell the IC. Here's a site that built it without the IC.
http://home.cogeco.ca/~rpaisley4/LM3909.html
BlueRoom, that's a really good example for noobs. Who needs Eagle anyway?
Inside every little problem, is a big problem trying to get out.
I can't take credit for it, just something I found and about 20yrs ago I built a LM3909 flasher when you could actually buy the IC.
I've added their site to my links page
Last edited by blueroomelectronics; 21st October 2007 at 08:07 PM.
I tape the leads of a bright LED to the sides of a 2016 lithium cell. This assembly is inserted into a balloon then filled with helium; used to measure wind speeds at night.
these days we have led flashers all in one...
if we don't need it to flash in a special way..there is no need for circuits...
just a led flasher does the job
To make it easy, just tape a few button cells together to get about 4.5 V and then put a Flashing LED connected up to it, and now you have a flasher, the easiest you could possibly think of.
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