simple keep the power on briefly cct

[nafifics]

Hi folks! First post here, I have a question regarding what should be a simple electric circuit and I hope you can help.

I want to add a light circuit to a project that has 2 other light circuits already. I want this 3rd light circuit to remain on very briefly (one or 2 seconds would be enough) when power is cut but not the other light circuits. I believe a diode and a capacitor will do the trick (an in-line diode and a capacitor across power (5V). I dont know for sure so I'd like some confirmation that this will work and is there an online program that will allow me to caculate to cap and diode specs? Other than 5V power I don't know the current required yet, but I can measure it if needed. It's a circuit with 4 leds powered from a flasher board.

Thanks very much in advance.
Jeff

 

[ronv]

Fader

If it is a vanilla led drawing about 15 to 20 ma something like you said will be good.

 

[4pyros]

10,000uf whats that a super cap. LOL

 

[ronv]

No, it's just an electrolytic. 16x25mm. But it is $1.50.

 

[nafifics]

Thanks for the replies everyone, and the cct ronv! Unfortunately I don't know the specs of the flasher cct I am trying to briefly keep power to. I would assume low current as the 4 leds do not flash simultaneously. I have been told the diode forward voltage is 0.7VDC so I will have to boost my input power to 5.7VDC to keep 5VDC to the flasher cct, correct? The graph shown shows that this will be sufficient, I think even half a second will be enough.

 

[4pyros]

I have been told the diode forward voltage is 0.7VDC

You can use a Schottky diode or two normal ones in Parallel to lower the voltage drop.

 

[ronv]

Is the light you are trying to keep on a string of 4 leds? If so are they in parallel or series. If they are in series the power is probably more than 5 volts from the flasher. If in parallel the current is probably higher than the one in the simulation.