HELP on voltage regulator

[airsoftmode]

Hi, I am going to be running a 11.1 lithium pack and two circuits, one to power an led driver, one to power a soundboard. The soundboard has a max voltage input of 4.5v so I need a voltage regulator.

Would this regulator work to bring the voltage down to 5v?
http://www.radioshack.com/product/in...6&tab=features

I figured I could then use a resistor to get it all the way to 4.5

Or should I just try and find a resistor to get from 11.1 to 4.5

And how do voltage regulators get wired? I see three prongs.

[Jay-gon Jinn]

It will get very hot trying to reduce from 11.1 volts down to 5 volts, and may need to be heatsunk itself.

[xl97]

regulators:

1 pin = GND
1 pin = V++ (power in)
1 pin = regulated power out

usually..and it depends on the schematic/layout for the one you buy.

also I think they also can loose power to heat..

[airsoftmode]

Hmm, so what is the benifit of opting for a regulator over using a resistor?

[Strydur]

A regulator is a much more sophisticated resistor. A resistor cant adjust when voltage starts out high or starts to drop off so the actual voltage will fluctuate but with a regulator you will keep a good solid 5v.

[neophyl]

A resistor controls CURRENT not voltage and as such isnt suitable for what you are trying to do. As resistance and voltage are linked in some ways its easy to be mislead.

You want the voltage regulator. Depending on the amount of current the sound board draws it may or may not need the heatsink. The regulator would be dissapating 6.1v (11.1 - 5) at whatever ma the sound board needs so if the sfx draws 1amp then thats 6.1watts, however if the sfx only draws 100ma then that would be 0.61 watts. Without knowing the current requirements of the sfx board its not possible to say if the heatsink on the regulator will be needed. You can try it and see if it gets hot. If it does then add the regulator. As it wont be driving the leds too, only the speaker it might be a reasonable amount.

BTW the MR board will run fine at 5v so you wont need anything extra to drop the .5v If you did want to drop it though you would use something like a diode not a resistor.

[Novastar]

I've said it like 3 times before, but... I *LOVE* it when Neophyl posts. Best. Posts. Ever.

To add to this, if other new folks read this on voltage regulation...

* It's not a good idea/standard practice to begin with (for example) a 12v battery solution... only to then use a regulator to limit the voltage to like 6v or 5v--it's a bloody waste of energy.

* If you MUST go "over" voltage in combination with a board that only likes less... don't be shaving off much!! For example, use a 7.2v pack with an MRFX board (~6v max)... and regulate it to 6v. Better yet, just give it 6v if you can in the first place.

* If your battery solution's voltage is skirting right on the edge of your board's LITERAL maximum voltage... you should use a regulator--even if it "seems redundant". For example:

Your Board's LITERAL max = 6v
Your Batteries = 6v... and often read 6v+ at full charge / brand new...
= add a 6v voltage regulator

Now... you do not HAVE to do this... but... it's not a bad idea to ensure the board's longevity.

[Onli-Won Kanomi]

Neophyl and Novastar posts are always LED-brilliant.

The mention of heatsinking the regulators brings up another question for me...

I was looking today for IC 12V regulators [for possible use bringing down the voltage of a quad pack of trustfires to use with US2.1] and I saw they were available in both "insulated" and "non-insulated" versions and am wondering: IF one was going to heatsink a voltage regulator then which type should one get; insulated or non-insulated?

I try to remember that with electronics "insulated" sometimes only means electrically insulated not necessarily thermally insulated so I'm wondering would the 'insulation' on insulated regulators interfere with effective heatsinking and I should get the bare ones or would there be some other reason the insulated ones might be preferable?


BTW this is the site with the voltage regulators I found...I was looking for 12v but they have lots of others;

http://www.tme.eu/en/katalog/voltage...lated_100215/#

[Novastar]

Onli... that is a good question, and I don't honestly know the answer. I imagine it won't be all that important since you'll want to "shield" the regulator from touching anything you don't want it to touch anyhow.

Aside from that though... if you're doing what I THINK you're doing... which is taking "14.4v" (possibly almost 17 "real" volts while not under load) and you're going to throw those into a USv1 or USv2 board... I wouldn't bother...

If I were you, I'd stick to an 11.1v pack, and not bother to waste a drop of current/voltage (no regulator)... and it should yield what you need for quite a long time (12 "real" volts) until the battery life is... oh I dunno... halfway down?? Maybe only a 1/4 of the way down??

Anyhow... I personally think it'd be a better solution.

Now you might be saying "hey, I want to run a Rebel 'fully' with all 3 Rebs on all the time". Well... you'll certainly be pretty close to doing so most all of the time with the 3 x Li-Ion setup. I doubt you'd notice the difference from throwing 11v at it vs. 12v... maybe up until the battery life was REEEAAAALLY low.

That's my 2 cents, but... naturally if you want to "shunt" 17v into 12... you're going to be dissipating ~5w and that is essentially like the heat from a Lux K2 @ 1.5A with a fwd v of ~4v (4 x 1.5). It won't be pretty. You'll have to heatsink with a TRUCKLOAD of metal... and... I don't know if it's even possible without a special way to mount the regulator.

Dissipating 1w or 2w isn't that big of a deal (in a saber)... a little more is trouble, and 4w or more would be what I'd think to be not worth it!

[Onli-Won Kanomi]

Hmmmmm you are right, Thanks for saving me from a big mistake - that was a dumb idea *DOH!*

Yes a 11v pack/3 Li-ions would be more sensible...but wouldnt a 12v regulator still be a good idea just so that when the Li-ions are freshly charged they arent giving the US2.1 over the 12V max the US is rated for?

Or maybe I'll try the 8aaa 12V pack available in the TCSS store but there probably won't be much runtime with that?

Don't mind me...feeling particularly dumb tonight...-sigh-