Hello,

How would you modify the below circuit to cause the LED to flash (based on the top left diagram) ? Thanks in advance...

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hi,
Its not than simple.

You could look at the LED's that have a 'in built' flasher, I have some RED leds that flash at about 1 second, when you supply 5Vdc thru 12Vdc

The #1 circuit would need to be modified to give a smoothed dc volatge for the Flash LED.

You may know this, but the circuits are not isolated from the mains and can be a electrical safety hazard.

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Didn't know that existed.

I have a few schematics for 12Vdc flashing circuits using transistors but when I wire them, the leds stay lit and don't oscillate. Don't know enough about electronics to know why... any ideas ? Below is the circuit I'm working with.

Thanks

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I am curious what are you trying to accomplish?

Just a blinking LED? Do you have to use the circuit the you first posted?
You said your new so I figure you are just playing around, or are you Modding something?

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try this :
LED Flasher/strobe Circuit

and will be like bellow :
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Well I am surprised that Eric, being an old hand at electronics, did not suggest this:

Digi-Key - HT40-ND (Littelfuse / Teccor(R) Brand Thyristors - HT40)

A DIAC relaxation oscillator. If you look at the data sheet you will see a phase control circuit. If you change the RC time constant and replace the TRIAC gate junction with your resistor and LEDs and put a diode bridge in front, you will get a simple AC powered LED flasher.

Or leave the time constants about the same and use a HP LED for a 60's strobe light

 

hi.

Nice catch.!

These days I have my head so far up my 'datasheet' I overlook the obvious.

I'm surprised you didn't suggest using an AVR...

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Eric " Good enough is Perfect "
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But I would be suggesting ARM

Actually I would not expect a micro generation engineer to see it, never mind techs or noobs. I supposed that makes you old school and me a tweener.

 

Does it have to be an LED?

Will and neon lamp do?

Connector a resistor, diode in series and a capacitor in parallel with a neon lamp and it will flash.

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He was saying LED... The DIAC actually works on the same principle- the voltage builds up on the capacitor until the breakdown voltage is reached and it turns on until the the current drops below the holding current.

You can of course get much brighter LEDs than you can neons... assuming you can find any neons these days.