# Noob here needs help with simple LED project, any takers?

#### WorldWideBum

Joined Mar 30, 2014
4
Hello geniuses of the electronic world. First of all I suck when it comes to messing with circuits because I simply don't understand them like I would like, however, they have gotten the best of my curiosity at this point and I want to try to construct a simple LED circuit for my project. I am pretty sure what I want to do has been covered here in the forums somewhere but my problem is, I don't know exactly what it is I am looking for so please excuse this post and accept my apologies if this has been covered to death. With that, here is what I want to accomplish and being a complete ignoramus with this stuff, I need someone to hold my hand through it basically:

I am building a marionette that I want to put a few LED's through out. I want to have 2 LED's for the eyes, I want to use the ones that will slowly change colors, rgb's? I want a red one to put where a heart would go and I want the LED to pulse like a heartbeat. Blink blink, fade... blink blink, fade and I want it to have 5 white LED's that stay lit controlled with a 9 volt battery and have an ON/OFF switch wired in.

I've included an attachment of what I'm trying to do. I know what I want but have zero clue how to get there.

I am COMPLETELY oblivious as what to do to make this happen including what to buy. I have no clue about resistors, timers, capacitors, or what types of LED's to purchase.

Any help would be GREATLY appreciated, a shopping list, the best place to purchase and diagram of how to wire it.

Thanks a million in advanced!

#### Attachments

• 84.9 KB Views: 59

#### THE_RB

Joined Feb 11, 2008
5,438
Hello and welcome to the forum.

The white LEDs are easy, they just need a resistor each.

The flashing red LED is easy, they can be bought off the shelf and usually don't need a resistor (depends on your battery voltage).

The eyes will be hard. Colour fading RGB LEDs can be bought off the shelf, but each will fade at slightly different times so they will get out of sync and after a minute will be showing different colours to each other. That can look cool too, I did a small LED sign with colour fading LEDs and they looked good once they got out of sync.

But if you want the eyes to be synced that is going to cause some issues. Possibly the easiest way to fix it is to use ONE fading LED, and some mechnaical construction like a split "light pipe" so the light from the one LED goes to both eyes.

#### wayneh

Joined Sep 9, 2010
16,114
For the whites, I'd try to put two LEDs in series with a resistor, to save a little battery power. Using the same 10mA passing thru one LED, it can instead pass thru 2 LEDs, so that the battery does not need to supply 20mA for 2 lights. It's not as simple as RB's suggestion of one resistor for each LED, and if you don't care too much about battery life, just go ahead with the simple approach.

For the reds, just how much like a heartbeat pattern do you need? Simple flashing is very easy as noted. A lub-dub double pulse could be more challenging. The brightness of an LED is determined by the current passing thru it, up to the point where the LED is destroyed by excess current. Simulating a heartbeat realistically might require a microprocessor to control the current in a pre-programmed profile. You would use PWM modulation, with the duty cycle controlled by the µP. This would be easy for the folks that know how, but a very difficult learning curve for a noob. It would be easy if you could find a commercial example to hack. Those LED candles you see everywhere use this approach and it would be easy to repurpose the IC from one of those. But you need a heartbeat pattern, not a flickering candle.

I think RB's idea of 1 LED with two eyeholes is the way to go.

#### WorldWideBum

Joined Mar 30, 2014
4
Thank you both very much! This is the stuff I'm looking for and can tell this is going to be a very painful learning process as I am having to look up and get some understanding of all the terms and symbols you all use.

It looks like the first thing I need to think of is what size the LED's are going to be & the power.

I am really liking the idea of a 9 volt for my power source. As far as LED's go, what size bulb (watt?) would be optimal if I have 8 LED's running off a 9 volt?

I have 8 of the par 64 LED stage lights that can do all that programmable stuff, so I'll have to look more into what "...PWM modulation, with the duty cycle controlled by the µP" means. Lmao, that's gonna take me an hour just to decipher that one sentence, but I'm up for the challenge.

I found a site that you can plug some information in and it tells you how to wire a simple circuit, but the add-on's I want to incorporate aren't included in their diagram.

I have the brain of an toddler when it comes to this stuff because I've never really figured it out like I have with so many other things, that's why I'm confident, with your all's help, it can happen.

Again, much appreciated!

#### wayneh

Joined Sep 9, 2010
16,114
PWM is just like flipping a switch on and off really fast, much faster than you can see, say 80kHz. The more time it's on (the duty cycle), the brighter the light appears. You can dim the light by leaving the switch off more of each cycle. While it's on, it's drawing full current and is at full brightness. Off is off. This digital scheme is more efficient because you don't use a resistor to burn off the excess power when you want to dim to say 50%. That's called a "linear" solution.

I would look for 5mm LEDs labelled "super" or "ultra" bright. Those terms get thrown around with candle power ratings like 30,000mcd. You should know that the focusing effect of the lens can be used to goose that number up. The LED may produce very little light when viewed off-axis. But modern LEDs supplied even 5mA can be very bright. You might mount diffusers in front of them if you want a wide viewing angle.

#### Bernard

Joined Aug 7, 2008
5,285
Eyes, in sync., seperate drivers for each color, 3 color R-B-G LED- Cree PLCC4 SM , All Electronics # LED-259, 3/ $1.00 LED Red, # LED-912 LED White # LED-918 Cat# LM556 [ 2X 555 ] ,$ .35
Cat # 4017, $.60 Cat # MPSA13, 5/$.50, NPN darlington
Solderless breadboard, Cat# PB-840, \$7.65, might add some pre-formed jumpers.

Just a suggestion of possible parts.
'would help if we knew your approx. location to suggest parts suppliers'
How large is marionette?

In " find box" this page, top right, put in Bill's Index, lots of ckts on 555's, flashing & throbbing, 4017 patterns. Can be modified to fit your needs.

Last edited:

#### WorldWideBum

Joined Mar 30, 2014
4
Excellent! Thanks so much! I'm starting to become familiar with the terms and getting a small understanding of how things are working together. I've found some beginner kits on eBay, I may snag one and just start experimenting.

I'm familiar with some of the parts you had mentioned Bernard from scouring the forums. Thanks so much for replying, this is the information I'm looking for!

#### wayneh

Joined Sep 9, 2010
16,114
FWIW, you should be aware that these things exist (there are many others). You might be able to hack such a device to give you a signal that could control your LEDs. Maybe you can find one with LEDs in it already.