Please help with a (hopefully) simple project

TOTC

Newly Enlightened
Joined
Nov 12, 2004
Messages
161
Hi all,

I want to build a metal photo frame with LEDs around the outside of it. I would like to build this so that it can be plugged into the wall and safely be left on. This will be a gift to someone.

I have 25 5mm LEDs (the ones that usually run off of CR2032 batteries), the frame materials, and really that's about it. I know nothing about wiring, I've never soldered a thing in my life (nor do I even own a soldering iron), and I really don't know where to start.

Can you guys help me out? What is the simplest way to wire such a thing? Will it require true soldering tools and skills, or can I use something like Solder-It? I am looking for a parts list and an overview of what to do.

If you can help me out, please explain what you mean under the assumption that I am completely ignorant. I don't know jargon or have any past experience with this sort of thing :(

Thanks!
 

Illum

Flashaholic
Joined
Apr 29, 2006
Messages
13,053
Location
Central Florida, USA
usually powering a LED assembly using DC is as simple as putting an resistor in the equation and your done...when it comes to AC-DC, the circuitry usually gets quite complicated.

My guess of the simplest way would be to buy a "wall wort" wall mounted stepdown from radioshack [ratshack] and build from that DC output up.

Im not an experienced modder, hopefully someone will chime in
 

TOTC

Newly Enlightened
Joined
Nov 12, 2004
Messages
161
Thanks, I appreciate it. I grabbed an old wall wort I had (funny enough it is from Radioshack) and looks like you're right: the equation is simpler than I realized. In the pics below I just stuck an LED into the contacts, dropped the adapter down to 3V (it has a switch from 3V to 12V) and plugger 'er in.

So will resistors (as you mentioned) still be needed? Will I overdrive these LED's without resistors? The adapter says it can deliver up to 1000mA, but I don't know how much it is actually feeding the LED.

Finally, will this be as simple as the childish diagram I've made below? Can I just run the LED's like Christmas lights to create one big circuit? Or is something a little more complicated in order?

radioshack.jpg

diagram.jpg
 

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hi,

You should probably use a constant voltage wall wart just in case someone
switches the unit to a higher setting and blows all the LEDs out.

The right way to drive LEDs with a wall wart is to use a resistor.
You can drive three LEDs in series at 12vdc with a 75 ohm 1/8watt resistor.
This means you can wire up 8 strings in parallel each with their own 75 ohm
resistor.

It might also be possible to drive the whole 25 LED string with a single
resistor and diode connected to the ac mains, but this would not be as
safe as using a wall wart. The resistor would be around 1500 ohms and
would have to be rated for 2 watts, and would have to be mounted in
a way so that it gets free air flow so it doesnt overheat.

There are other voltages you can run at too, so if you have any other
wall warts let us know the voltage and current outputs of them and
we can offer alternative circuits to drive your LEDs.
 
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