/diy/ - Do It Yourself

[Anonymous No.323717]

I'm sure I'm going to get my dick kicked in for this one but here goes.

I'm a model maker (Plastic, milliput, glue and paint) and I would really like to try installing some LEDs in models. Nothing fancy just push button/plug in and it works. The problem is I have zero experience with wiring or anything of the kind.

Does any one have a simple tutorial for setting up a LED? I mean "Buy LED + battery, push together" simple? I've tried looking up a few and they all want to explain the science behind it (which is great, but not what I'm looking for), when I just want to purchase exactly what I need, put it inside a plastic shell and push a button/push a plug in.

[Anonymous No.323721]

- A button or a switch
- A battery
- Some wire
- A LED
- Some kind of resitor to prevent overload, I guess. I'm not very good with electronics either.

You know how to solder it already? That's most of it then. Someone else might want to tell more about the resistor part though...

[Anonymous No.323724]

http://led.linear1.org/1led.wiz

This shows the basic connection and calculates the resistor value. Cut the wire at any convenient position and insert switch there.

[Anonymous No.323742]

Here you go OP

[Anonymous No.323744]

Here's an example:
-you want to power a LED with 9V battery (V)

-the LED has a maximum current of 25mA, so we'll use 20mA (If)
-the LED has a forward Voltage drop of 2V (Vf)

Vr = V - Vf
Vr = 9V - 2V
Vr = 7V this means that the resister needs to drop 7V

R = Vr / If (ohms law)
R = 7V / 0.02A
R = 350 ohms

Answer: use a 330ohm or a 470 ohm resister
330ohm raises the current, making it a little brighter
470 ohm lowers the current making the LED last longer at the cost of a little brightness.

Check (If) using the 330 ohm resister:
R = Vr / If
330 = 7V / If
If = 7V / 330ohms
If = .0212
If = 21mA
this is fine, so use the 330 ohm resister

[Anonymous No.323775]

If you want, you could use button/coin cells. They are usually low power enough that you won't need any additional current limiting. Just connect the led directly to the battery. Another neat thing about button cells is that you can fit the cell between the legs of a led, and then just wrap everything with heat-shrink or electrical tape if you want make it more permanent.

Of course building a proper circuit is highly advisable, but not absolutely necessary

[Anonymous No.323784]

Oh, found this while searching, neato. "Throwie" seems to be the name for this kind of things, google finds all sorts of guides and examples.

[Anonymous No.323791]

>>323784
I searched them and they are perfect. I knew they existed but my mind blanked them until they were brought up.

Thanks to you bro.

[Anonymous No.323829]

>>323775
>>323784
Throwies just ignore current limiting. It's trading convenience for lifetime.

[Anonymous No.323883]

If you want to use more than one LED, you can connect them in series up to around 80% of the supply voltage. So e.g. if you have 3x LEDs each with a 2V drop and 10mA current, and a 9V supply, the dropping resistor would be (9-6)/10e-3 = 300 Ohms.
You need to leave ~20% "headroom" so that the current doesn't vary too much with the supply voltage (as the battery discharges) or process variation (an LED with a "nominal" drop of 2V might actually drop 1.9V or 2.1V).
Connecting in series is more efficient; if you wired the same LEDs in parallel (each with their own series resistor), you'd use three times as much current and thus three times as much energy.
You can buy constant-current LEDs which don't need a series resistor, but they're a lot more expensive than a normal LED and a resistor.
If you want to run an LED from a 1.5V supply, you need a "Joule thief" (a simple boost converter which can run off a very low supply voltage).