Getting started with LEDs

[hoggworks]

Hey all!

I’m looking to finally start implementing LEDs in some of my prints, and as a very first step I was wanting to connect about 6 diodes to a 9V battery in a battery case.

I know that resistors are necessary, but am pretty clueless about how to use them; can anyone point to a tutorial for hooking up 6 LEDs to a battery casing? Eventually I want to progress to arduino, but figure I should get the basics first.

Thanks!

 

[13doctorwho]

The easiest way is to create two strings of three LEDs. Assuming the cheap Red, Yellow, or Green LEDs each string will need a 150 Ohm resistor. Keep in mind the LED's are polarized so they can only be connected one way.

Here's how the math works.
Each LED probably needs about two volts. So three in series (end to end) is 3LEDS X 2Volts= 6 Volts

You're using a 9 volt battery, so 9 Volts -6 volts= 3 volts. That's the voltage across the resistor.

The standard red, yellow, or green LEDs require 10 to 20 milliamps of current. More current is brighter (as long as you don't exceed the rating and burn them up). The current through the resistors and the LEDs will be the same since they are in series. So resistance=voltage/current. So the resistor has 3 Volts / 0.02 amps = 150 Ohms.

Duplicate that circuit for the other three LEDs. Connect the resistor from both strings to the positive of the battery and the negative leg of the last LED in both strings to the negative.

VERY IMPORTANT: You need to find the voltage and current rating for the LEDs you use and do the math accordingly. White LEDs, Blue LEDs, RGB LEDs all require different voltage and current. The math works the same. if it's a 3.2 Volt LED... 2 LEDs per string... that makes 6.4 volts... resistor Voltage is 9-6.4 V so 2.6 volts... say the current is still 20mA (0.02 Amps) that gives you a resistor of 130 ohms. It also means three strings of two connected the same way as the other example.

 

[3Dsf]

Check out:

Lights for model makers: technology and techniques

Welcome to my writeup on lighting models. You've come to the right place if you want to learn more about illuminating scale models of various kinds – spacecraft, railways, dollhouses, cars, and so on. And I don't mean shining external lights on the model, of course. I'm referring to the technology

sites.google.com

 

[Antsnest]

I wrote this 20+ years ago and is rather out of date as the technology has moved on a lot since then, but the concepts are still sound Shedding Light on LEDs
You mention 9v battery and my first question would be 'do you specifically have to use a 9v battery?' - It may be a space limitation thing which is fine but generally the PP3 type batteries do not have a lot of 'capacity' - the ability to deliver their charge over time, and are not great for running LEDs if you don't want to be swapping them out regularly. Lower voltage cells like AAs have far greater capacity and if you have space, using a few AA's in series to get the voltage you need will give you a much longer lasting solution.

 

[JimmyB]

This video tutorial on getting started with LEDs might help as well. She also has a video on animated LEDs.

 

[modelerdave]

I'm going to tell you not to bother with your own resistors and buy pre-resistored LEDs from places like Evan Designs, HDA Modelworx, and others. Many of them also come with simple built-in lighting effects so you can do basic flashing, fading, pulsing, etc., without the need for an Arduino.

I find soldering resistors onto LEDs to be a huge pain in the ass, and avoid it whenever possible. YMMV.

 

[JGG1701]

Very

Hey all!

I’m looking to finally start implementing LEDs in some of my prints, and as a very first step I was wanting to connect about 6 diodes to a 9V battery in a battery case.

I know that resistors are necessary, but am pretty clueless about how to use them; can anyone point to a tutorial for hooking up 6 LEDs to a battery casing? Eventually I want to progress to arduino, but figure I should get the basics first.

Thanks!

Very great source for all your lighting needs.
Tell Jerry that Jim sent ya.

LED Lighting

-Jim

 

[hoggworks]

Very

Very great source for all your lighting needs.
Tell Jerry that Jim sent ya.

LED Lighting

-Jim

Thanks for the link! I'm at the "looking for info first" phase, though I think my immediate needs would be served by getting a battery pack and a bunch of 12v diodes that already have resistors installed, so save me some initial headaches.

 

[hoggworks]

This video tutorial on getting started with LEDs might help as well. She also has a video on animated LEDs.

Thanks, I'll check it out!

 

[hoggworks]

The easiest way is to create two strings of three LEDs. Assuming the cheap Red, Yellow, or Green LEDs each string will need a 150 Ohm resistor. Keep in mind the LED's are polarized so they can only be connected one way.

Here's how the math works.
Each LED probably needs about two volts. So three in series (end to end) is 3LEDS X 2Volts= 6 Volts

You're using a 9 volt battery, so 9 Volts -6 volts= 3 volts. That's the voltage across the resistor.

The standard red, yellow, or green LEDs require 10 to 20 milliamps of current. More current is brighter (as long as you don't exceed the rating and burn them up). The current through the resistors and the LEDs will be the same since they are in series. So resistance=voltage/current. So the resistor has 3 Volts / 0.02 amps = 150 Ohms.

Duplicate that circuit for the other three LEDs. Connect the resistor from both strings to the positive of the battery and the negative leg of the last LED in both strings to the negative.

VERY IMPORTANT: You need to find the voltage and current rating for the LEDs you use and do the math accordingly. White LEDs, Blue LEDs, RGB LEDs all require different voltage and current. The math works the same. if it's a 3.2 Volt LED... 2 LEDs per string... that makes 6.4 volts... resistor Voltage is 9-6.4 V so 2.6 volts... say the current is still 20mA (0.02 Amps) that gives you a resistor of 130 ohms. It also means three strings of two connected the same way as the other example.

I was thinking about getting some of these to start, as they already have resistors added: Amazon.ca

Which I *think* means I can just connect them to a battery/battery pack, since I'm initially not needing any lighting effects, just something that I can switch on and off.

 

[hoggworks]

I'm going to tell you not to bother with your own resistors and buy pre-resistored LEDs from places like Evan Designs, HDA Modelworx, and others. Many of them also come with simple built-in lighting effects so you can do basic flashing, fading, pulsing, etc., without the need for an Arduino.

I find soldering resistors onto LEDs to be a huge pain in the ass, and avoid it whenever possible. YMMV.

I think that'll be my first step. I want to get programmatic stuff at some point, but I should learn how to crawl before I try to run.

 

[Sluis Van Shipyards]

This video tutorial on getting started with LEDs might help as well. She also has a video on animated LEDs.

That's one of the ones I've used. Her channel is great. I love her Fallout 4 Dogmeat armor for her Corgi! I thought she was a member here, but not sure.

 

[rjenkinsgb]

I'd suggest two LEDs per chain, not three.
The voltage of dry cells drops by around 30% over their normal lifespan, before falling sharply when they are dead flat.

In other words, a "9V" battery will be down to 6V before it is fully exhausted & you need to design for the LEDs to work acceptably over the 9V to 6V range.

With three LEDs, needing near 6V to just conduct, the brightness will change drastically over the life of the battery. Sticking to just two LEDs means the percentage change in voltage across the series resistor is a bit lower, roughly 5V down to 2V.

For the resistor value, subtract the total of the LED forward voltages from the supply voltage, the multiply by 50 if you want 20mA, or multiply by 33 if you want 30mA. Use the nearest standard value resistor.

(The multiplier factor is 1000 / current in milliamps; ie. multiplying the voltage by 50 to get Ohms means the current is 1/50th amp or 20mA).

If you use ultra-bright LEDs, you may be able to use 1mA or even less, which will vastly prolong the battery life compared to low efficiency, high current LEDs.