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Running LED's with a wall outlet Answered

I have a question,

I am thinking of making a Pepakura Iron Man mask for my father for his desk at work.  I have big plans for this, but the biggest thing I want to do is had the Eyes light up. 

What all would i need to do this?  I would think using LED's would be the ideal way to go.  I dont really want to use batteries to power it, as I would like it to run off of a wall plug, and perhaps even have a switch to power on and off.

Any ideas?  I've looked all over, and I cant really find a deffinate way/means to power it through an outlet....most all just mention batteries.  I know it can be done though :)

Any help is GREATLY appreciated!

17 Replies

user
electrobrandino (author)2011-01-12

Could i just use a DC Jack and Plug from Radioshack to power the unit?

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user

A small 9V transformer such as this with a 5V regulator should give enough power to safely run as many LED's as you need. For a bit more, you can get a regulated 5V supply which will remove the need for the regulator.

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user

so would something like

http://www.radioshack.com/product/index.jsp?productId=3875402

work then? Im in the US so our outlets pin configurations are different of course ;)

This one is adjustable as far as voltage, and i think that should be enough mA....so other then this, all i would need is a jack to install in the unit (and all the leds, resistors and such of course

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user

oh, and it says that it is regulated :)

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user

You should be able to run quite a few LED's straight from it on the 4.5V setting, as well as any IC you may want to add to flash the LED's.

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user

well i have another question :)

when i calculate it up, i would need a 51Ohm resistor for each bulb if i ran it at 4.5v... The bulbs i found are 3.3v and 25mA and i am using 6 of them. (i want it bright :P )

I cant really find a 51 Ohm resistor readily available, so here is my question...

Can I bump it up to 9v and still run it safely? at 9v, i could use 100Ohm resistors on each bulb, which i can get very easily...

WIll this cause any other issues?

see here for the calculator i used.

http://ledcalculator.net/default.aspx?values=9,3.3,25,6,0

Thanks again for all of your help. just getting this info confirmed is helpful!

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user

About 8 ohms with the 6 LED's in parallel on the 4.5V setting should work. Alternatively, put them in two rows of three, straight from the supply, as 0.3V less than the rating should make no noticable difference to the brightness, and the supply will probably put out

The calculation is correct, although a single 30 ohm resistor would work just as well.

It doesn't matter about the exact value of the resistors, as long as they are reasonably close.

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user

so, 2 Straight rows with 3 bulbs each...would i need a resistor at all? and if so on which line or both..I think im confusing myself now haha.

sorry im really new to the LED scene :P I've re- soldered old game system boards and things like that but these Little LED's are kicking my rear! :)

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user

2 rows of 3, on 9v will not need a resistor. Just treat them like any other component, and if in doubt apply V=I*R.

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user

I got all of the supplies but im having trouble wiring up the DC jack...there are NO instructions on if one needs to be the + and the other - or what....anyone have any ideas? there is a pole in the middle to be soldered to, and a tab on the outside. here is the plug i got exactly

Size M Panel-mount Coaxial DC Power Jack

http://www.radioshack.com/product/index.jsp?productId=2102486

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user

FYI i sent you a PM with one final question ;) I am also going to subscribe you haha

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user

Ah, that makes sense....i was still thinking 4.5v and trying to figure out how you came up with that! haha.

Thanks for the help! that may be the way to go, as I play to do 3 per eye socket, so two rows of 3 will make it easier to wire up :)

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user

or even at at 6v....that calculator shows 110 Ohm for each bulb...again, easier to obtain then a 51Ohm (could do a 10Ohm and 100Ohm together)

Any ideas? haha

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user

110 ohm per LED will work.

For resistors in series, you just add the resistances.

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user

Oh, and after looking at it again, it appears it would be a 100Ohm resistor for every set of 2 bulbs...

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user
d77uk (author)2011-01-14

If there's a PC on the desk, could you not hook it up to a USB port? They output 5v DC.

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electrobrandino (author)d77uk2011-01-14

I could...hmmm....the wall would give him more options in case that's not where he wants it tho...something to consider tho

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