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.
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.
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.
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.
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. **broken link removed** **broken link removed**
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.