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Easy blinking LED circuit help please

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TecNicL

Computer
May 21, 2003
1
Hello all!

I need to construct a circuit that will cause an LED to selectively blink or stay on steady. The brightness needs to be adjustable and, when blinking, the rate of blink needs to be adjustable. The blink rate need only vary from about 1 second to about .25 second at 50% duty cycle.

I have found on the web a circuit made up of a 555 timer set up as an astable multivibrator with a few potentiometers to vary the blink rate and brightness and powered by a 9V battery. This works very well to blink the LED, but not being an electrical engineer, I'm not sure how to alter the circuit to make the LED stay on steadily.

The LED in question is rated at:
Forward Voltage: 2.4VDC +/- 0.3V (5VDC max)
Forward Current: 40mA max
Reverse Voltage: 6VDC
Power Dissipation: 100mW

Any ideas are appreciated.
SC
 
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not knowing the circuit, I would suggest raising the threshold slightly so your trigger could get under it, so to speak.
 
If your LED is switched on by taking the 555 o/p high, then you can keep the LED on by taking the 'trig' pin low.

If LED on when o/p is low then take 'thresh' pin low.
 
amidabadi,
any blinking circuits that i can use on 1 watt LUXEONS with speed control?manual or preset.appreciate the help.
 
if you want the led to stop just put a switch in series with the capacitor ... i dont know if you like it to be automatic ... if not this is a simple solution for you ...
 
You need to combine two timer circuits: an astable for blinking rate, and a monostable for brightnes/steadiness.

Astable should trigger the (retrigerable) monostable. Monostable should light LED.

By varying the frequency of astable, you adjust the blinking rate. If you adjust it very high, so that it retriggers monostable before it has time to go off, LED will never go dark. Additionally, while in blinking mode, you can regulate the brightness by varying monostable time constant, that is, the LED "on" time.
 
could just use the clasic astable curcuit...couple of transistors couple of resistors couple of capacitors (the product of the resistor and capacitor values gives an approx time constant it cant be dead on because of the variance in transistor trigger voltages) when you want to stop the flashing you open up one of the caps, which one you open decides wether it will stay on or off, as for the adjustable brightnes, a potentiometer in series with the led will take care of that, to keep your duty cycle at 50% just keep both sides at the same values.
site with schematic: just substitute the 1k resistor on one side for your led and series pot pot value of 1k would do well btw
 
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