Problems with astable flip-flop period

Hi,
I have built 2N2222 based led flasher with 1 greenish-blue led, I wanted the LED to flash at 1Hz rate. One strange thing I have noticed is that when I change the voltage from 3.6V to 4.8v to get more brightness, the frequency increases. I have designed other flashers too and I don't find the frequency & duty cycle reliable with voltage change. Has anyone else noticed this? Any suggestion on how to keep the precise timing of the flasher over a range of 2.7-4v? (I have used 10k resistors, 470uf and 22uf capacitors).

This would go much better if yopu posted a drawing or schematic.

Any suggestion on how to keep the precise timing of the flasher over a range of 2.7-4v? (I have used 10k resistors, 470uf and 22uf capacitors).

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Depends on what you call precise but if you want accuracy consider the use of a crystal oscillator.

Any circuit theat pins accuracy to a handful of capacitors and resistors will not be very accurate.

Ron

Use a 555. It does much better keeping the period and width constant as a function of supply voltage.