Hi
I want to build a very simple circuit to alternately flash 2 high power LEDs - the sort you get in cycle lights. I have seen numerous circuits, either using a bistable oscilator with 2 transistors, or a
Regards
Neil
The 555 will work at 9V, even 12 or 15V. So will "non-logic-level" power MOSFETs, such as ones by International Rectifier not specifically claimed to be "logic level". The "logic level" ones are also good for 9V as long as you can be sure the voltage never exceeds 10V. You can use a
555 to switch MOSFETs. Also consider 4000B series logic - good for all voltages 4.5 to 15 volts. 74C series logic is also good for at least the 4.5-12V range, maybe 15.Another consideration: Use 5V logic powered by a 5V regulator (7805 or the like) and have final logic outpouts drive gates of "logic level" power MOSFETs. The MOSFETs can still switch loads at voltages up to their drain voltage limits, 20 volts and up.
- Don Klipstein ( snipped-for-privacy@misty.com)
A 555 will do it. See:
Ed
That first circuit, Eccles-Jordan multivibrator, will alternately switch incandescent lamps directly. 2N2102 will switch about an amp in that circuit, 2N3904 is good for 200 ma.
Better than a 555 if you have to add transistors to switch the load (and don't need to vary the flash rate easily)
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"Bistable oscillator" sounds like a contradiction. Guess you mean astable (sometimes written as a-stable). This type of oscillators were ever build using electonic tubes, powered by up to 200V. Maybe more. There's no reason to use a 5V supply for transistorized oscillators. You can still use even
200V, choosing the right transistors of course. So 9V will not be a problem. That's not to say you can apply 9V to a circuit designed to be used at 5V. Currents may rise too high and blow the transistors. Actual components depends on the current required by the LEDs and the on/off timing (duty cycle). A 0.1s flash once an hour will not be easy to build this way.petrus bitbyter
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