Selecting a power source (non-battery).

Amaterasu · Post by **Amaterasu** » Fri Jul 16, 2010 1:23 pm

Hey all!

I'm looking to make a power source hub to power all the lights that I intend to put on would-be-built models in the future. It needs to be strong enough to drive ICs and LEDs, and I cannot forsee much else.

I have an adjustable power a/c adaptor from some chain store, commonly called a wall-wart. I heard that these are far from efficient and regular as a power source - but since the people of this forum seem to have used them, I don't imagine that they'd be much of an issue.

I'd like to take a more 'green' solution by making an adapter (or buying one) that uses a reasonable amount of energy to power a few LED lights. In the event that it is not possible, I'll cut right to the chase:

What voltage should I use to power my gizmos?

I realize that you can adjust components in a circuit for any voltage. Since I am going to use an outlet source, voltage is not limited to the power source (practically). My AC adapter is adjustable from about 2 - 20 V. I have projects that need to-be built so I don't have the luxury of selecting a V(s) to suit my needs. If I had to pick one, any one, a jack-of-all-trades, what source Voltage should I go with?

Suggestions, comments and questions are most welcome.

USS Atlantis · Post by **USS Atlantis** » Fri Jul 16, 2010 3:14 pm

My suggestion

Drop the adjustable/switchable adapter - I have one and from what I can determine, these are un-regulated

If you're running LED's and especially IC's, you'll want a regulated supply - it'll say on the adapter that it's regulated

Those un-regulated one's can vary the voltage by as much as 20% (set at 20, it could put out anywhere from 16v-24v) and that can blow LEDs and fry IC's, even with the proper voltage dropping put in for the 20v nominal

Your other option is to include a regulator circuit on any electronics you install

Myself, I work with 6v or 9v; fairly common; though I think some of the aftermarket electronics suppliers (Voodoo FX, DLM, etc) run theirs off of 12v

Amaterasu · Post by **Amaterasu** » Fri Jul 16, 2010 5:27 pm

Either I make a regulator or make certain that the adapter says that it is regulated.

Check.

Thank you! This saves me from burning out some ICs.

I'm still uncertain as to the voltage to use. If I go with 12V, I can always drop it down with resistors.... I suppose it comes down to the walwort or supply that I can find, doesn't it?

Is there a minimum voltage that I should be aware of for projects? For instance - if some ICs work with no less than, say, 9V?

Thanks for your quick reply!

USS Atlantis · Post by **USS Atlantis** » Fri Jul 16, 2010 5:55 pm

That's why I pick either 6v or 9v

I'm not aware of an IC, other than CPU's and perhaps PICs, that require more than 5v

Reason I normally pick 6v

LEDs come in two flavors - ~2v and ~3v - both go into 6v evenly - meaning you can use the lowest possible resistor value - even with the LED voltage total equaling the supply voltage, I still put in a 1ohm-10ohm resistor to insure non-blowouts - the LEDs will dim a little, but not enough to notice, and the extra protection of even the low-value resistors makes it worth it

Sparky · Post by **Sparky** » Mon Jul 19, 2010 3:36 pm

If you have ICs or other chaigng outputs resistors cannot be used as a voltage regulator.

Resistors are calculated for static (constant current) circuits, ICs that are changing their outputs will be constantly varying their current draw so a resistor should not be used.

Also please consider that a resistor is eating access power, and converting it to heat. A resistor will also become one more point of failure, solder joints pinch cuts or short circuits. If you can design out the resistor it is best to do so.