Circuit Design Question

Ok, I have a power source that outputs about .5 volts sometimes, but at other times as much as 12 volts. I want the power to illuminate an LED in both cases, without burning it out. I think I need a capacitor for this but I'm not entirely sure? Can anyone tell or lead me to a tutorial or circuit diagram that shows how to do this? Thanks!

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tech-king10 years ago
1) a Vreg would get hot! a heat sink is a must 2) why does the power supply fluctuate?? maybe its time for a new one 3)if its alternating current, a choke could help, because it would induce a mirror current, opposing the voltage change and smoothing the transition.
As long as the voltage drops were not total collapses......that might bring further problems, don't you think?
a choke opposes change. as such, it would smooth the voltage change. unlike a Vreg, its passive so needs not electricity or bias voltage. i don't believe it would cause further problems. but WHY is your power flickering?
Joe426 (author)  tech-king10 years ago
this power is coming though ethernet cable, with regular ethernet - only about .5 volts is coming through, but if the port is plugged into POE - power over ethernet - as much as 12 volts can come though.
tech-king Joe42610 years ago
why the Ethernet?? I'm obviously missing something hear. a linear or battery supply would be cheaper. if you want an activity LED, there are already ones on the Ethernet jacks; you could simply solder on some wire and another led.
Ok, I understand what you mean now,
zachninme10 years ago
Try hooking up a 100uF capacitor and a 5v regulator. From there, you should be able to scale down to whatever you need for the LED. 100uF may or may not be enough, not sure how fast it fluctuates -- experiment ;-) Both you should be able to get from any basic electronics store -- although I can't guarentee Radio Shack (unless they still have "bins"-- that is)
Duh on me......I went the long way around, didn't I ? :-) The regulator would could for that range.
Joe426 (author)  Goodhart10 years ago
a regulator as in a potentiometer or...??
Goodhart Joe42610 years ago
a Voltage Regulator (link) as in a 7805

The only problem I see is when the voltage drops below the threshold (7.2 v for the 7805) for the regulator, the circuit will not function.
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