help wiring ironman eyes

hey guys i'm new to the building game and i've been doing some research. i would have gone with stealths eye lighting tutorial but my eye wells are a lot deeper than his were so the scrap plastic wasn't gonna work.

here's my idea.

i'm planning on 6 white LEDS (i think these are in parallel), running to a switch, then to a 9V. does this look okay? do i need a resistor? i have no idea about electronics other than the tiny bit i did during a few physics courses in university.

the electronics in the diagram are just for visual purposes, i'm guessing the polarity or something is all messed up.

THANKS

anyone? i'm really stuck here

You need to check, at the inside of LED, there is inverted L shape, that's negative.
So connect 3 LEDs in series as one group. The connect both groups in paralel.
Hope it helps

IMIM2 said:

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You need to check, at the inside of LED, there is inverted L shape, that's negative.
So connect 3 LEDs in series as one group. The connect both groups in paralel.
Hope it helps

thank you! this looks way more organized.

do i need a resistor anywhere?

Assuming you're working with 3 volt LED's yes you are going to need resistors. The specific type of resistor is entirely dependent on the specs of the LED's your going to use. Wire a 9 volt battery to a 3 volt LED and you'll have the opportunity to see thr magic smoke that makes things tick.

With no disrespect to epilepticsquirl, I've used the schematic on my arc reactor using 9V battery and it is fine. if you want to add precaution, just use 47ohm would be fine. Or you can buy 100ohm trimpot so you can adjust the brightness. Just don't try to connect single LED to 9V.

It might be fine now, but not using the proper resistor will diminish the life of your LEDs.

Use this LED calculator to figure your resistor needs and wiring diagram.

Thank you for the calculator Kevin.
Without the spec (which we normally don't know) the calculator will not calculate for us.
So, voltage drop normally for 10mm DIP LED is 3.5W, and current rating is 20mA.
Input that, qty of LED 6, and voila, exactly my schematic (except 1 ohm resistor which is nothing).
So again, adding a trimpot (tiny variable resistor) is a nice one to have, so we can adjust the brightness and yes, prolonging the life.
I am sorry, I tried to keep it as simple as possible on my earlier post.

this really helps a lot thanks everyone

voltage drop normally for 10mm DIP LED is 3.5W

What? That's not correct, even if you meant "5mm" and "3.5V".

If I have an unknown LED, I tend to use the following procedure:

- Connect to power supply via multimeter set to measure current
- Increase voltage until the LED is bright enough, or until 20mA flows, whichever happens sooner. Practically all small LEDs are OK up to 20mA.
- Using the multimeter, accurately measure the voltage you got to (often the voltage display on a bench power supply is not entirely accurate, so use the meter).
- Punch the resulting current and voltage numbers into an LED calculator.

You DO need a resistor, always (or effecively always). Using one particular value for all LEDs is NOT good enough. Failure to get this right WILL reduce the life of the LEDs, sometimes to hours or even minutes. White LEDs in particular tend to go purplish-blue if overheated.

Rules of thumb:

Voltage drop for blue LEDs (and white ones, which are electrically blue ones) is usually 3 to 4 volts.

Red is often 1.8 to 2V.

Modern LEDs, particularly blue, white and red ones and anything advertised as "high brightness", produce very intense light. This has two implications: first, you may need nowhere near full power (often around 20mA) to get a useful effect, especially if they're indicator lights to be viewed directly as opposed to illuminating things. The second implication is that many modern LEDs require similar safety considerations as for laser pointers, at least at short range. As with lasers it's pretty unlikely you're actually going to damage anyone unless you force yourself to stare into it for a long time, but don't be staring right at it as you apply power!

HF

Hfuy,
I tried to google on LED specs (as I mentioned, normally we don't know, and there are many LED manufacturers), and as you stated yourself, voltage rating is usually 3 to 4V (typical value). In here, I stated 3.5V.

Actually is not the voltage, but the current that is more important to LED
(unlike most of electronic components).
And as you stated, up to 20mA is normally enough for LED (and I checked on several 10mm DIP LED specs too).

Using Kevin's suggestion of LED calculator, and that's not mine or me saying, it gave 2 parallel set of 3 LED being series, with two 1ohm resistor.

Earlier I suggested to use 47ohm (try to find 1ohm at the store), or a trimpot just to be safe. I repeat that again on using trimpot, because it find it useful that we can adjust current value.

Let's entertain your comment, that "you may need nowhere near full power (often around 20mA) to get a useful effect". Say we only need 10mA. Go to the calculator and see what comes out of it.

Again, I tried to keep it simple so everybody can gain from it. Not everybody have variable power supply and multitester. Everybody has different knowledge on electronics.

If you want to help cephalofoil, please share your schematic, how to better set up 6 10mm DIP LEDs using 9V battery. Perhaps yours are better and longer lasting.

Sorry for double post.
And apologize for typo. it should be 3.5V not 3.5W.

Thank you for pointing it out

You have brought up another matter:
There is nothing wrong in using 9V batteries. Dimension wise is smaller, lighter in weight (compare to 4 AAA which will give 6V, if we want to have 9V than it is 6 AA / AAA). By calculation, a typical 9V NiMH rechargeable 170mAh will give about 4 hours to light up 6 LEDs. It has advantage and disadvantage. I used 9V batteries because:
1. Compact size
2. Lightweight
3. Can be use for LED strip (at 12V rating)
4. Firm and simple connection (to me)
5. Can be attached just by using magnets to the battery's body.

I made a calculation on both schematic (your and mine) and calculate the current.
With the assumption that typical working current for LED is 20mA, according to your schematic (schematic 1a.jpg) the voltage drop on each LED would be 1.5V. Or let say the voltage drop of LED is 3V, therefore the current passing each LED is 6.6mA (schematic 1b.jpg).

I calculated on my schematic using 47ohm resistor (schematic 2.jpg), and with assumption that the current drawn from LED is 20mA. Each LED will have a voltage of 2.37V. Without the R, current would be 20mA at voltage drop each LED at 3V.

Also from my schematic, it is shown that most of the power is used in LED, not resistor. Meaning most battery power is used to "power" the LED to produce light, not going to R and produce "heat".

Your schematic is much safer because the LED will work at less than half of its typical value. But I doubt it til even lit. Perhaps lowering the R value. My suggestion is pushing the LED to work at typical value. Will it shorten its lifetime? Yes compare to the other schematic, but this is at typical value, not over, vs. running at half of typical value.

Last thing, the picture shown by cephalofoil is three LEDs per eye. Cabling would be a little bit complicated using schematic 1.

Apologize for making it looks more complicated on a quite simple setup.

Those that getting lost following this, just pick a choice .
I'm not God, I DO make mistake.

Hey, IMIM2, in your first diagram, you put the switch in the wrong place. It would leave one of the eyes lit at all times! It should look more like this:


as far as Your led issue, just order these pre wired leds from ebay.
20pcs 5mm White LED Lamp Light 20cm Pre Wired 12V DC Free Shipping | eBay
they are super cheap and already have a resistor pre wired to each led. I just ran one big parrallel circuit and it works great. if i end up with burnt out leds, so be it. ill fix it then. but i dont foresee an issue.

, see, I can be wrong. Thanks for pointing it out.
I am not familiar with the pre-wired ones, let me take a look then.
I thought those are just added heat shrink tubing and cable only.

Personally, I use LED strip, it is easier to work with and very thin, but then again, its personal preferences. Plus, I got lots of it

With your latest schematic, it draws bigger current from the battery (60mA vs 40mA), and around 20% of the power goes to resistor (become heat vs light=less efficient). Not to mention more components (3 R vs 1 R), more cabling (3 at each side) and more soldering. And still the LEDs will run at the same typical values. Unless I foreseen something else.

There are several ways to set this up, with plus and minus on each setup.
Simple or complicated, it still can be explained mathematically.

I guess Helagak's idea for pre-wired LED would be the simplest of all. Too bad I don't have the setup, it just said it runs on 12V, so it'll just connect them in parallel (?)

Thank you for sharing a nicer drawn schematic.

Well, we're not comparing the same things here: my schematic is for 3.5V LEDs.

But the point remains that your schematics all show LEDs in parallel, which is not a good idea.

alpena lights. side mount chip-set LED strips. prewired with resistors, wire, monitary switch and battery pack. around $30. found at walmart

here is my vid. look at 3:50
foamhammer lights tutorial for alpena

I too am new at this stuff, and I figured out a way to "cheat". I just went to Dollar Tree and bought a $1 LED Push Light. I carefully took it apart, and just re-used the guts as needed. This way I leave the ohm calculations to someone else. The lights are pre-wired with the proper resistors for the amount of power.







I haven't assembled my eyes yet, but I plan on using the same methodology. Good luck!

cephalofoil said:

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hey guys i'm new to the building game and i've been doing some research. i would have gone with stealths eye lighting tutorial but my eye wells are a lot deeper than his were so the scrap plastic wasn't gonna work.

here's my idea.

i'm planning on 6 white LEDS (i think these are in parallel), running to a switch, then to a 9V. does this look okay? do i need a resistor? i have no idea about electronics other than the tiny bit i did during a few physics courses in university.

the electronics in the diagram are just for visual purposes, i'm guessing the polarity or something is all messed up.

THANKS

See what you started..... LOL
lots of options as you can see...

Hfuy said:

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Well, we're not comparing the same things here: my schematic is for 3.5V LEDs.

But the point remains that your schematics all show LEDs in parallel, which is not a good idea.

3V and 3.5V? So it's a so much a big deal therefore the schematic need to change drastically? Say your idea using 150ohm, so the voltage drop is 3V, do you know the impact is even worse to the efficiency? Do yu want me to explain it to you why?

How can my schematics show all LED in parallel? Mine is 3 in series (your term strings), then two strings are paralleled.
Show me why it is not a good idea? Can you pin point that?
I can pin point yours.

My schematics is backed up with the LED calculator, typical value of LED, calculation of current and voltage, and most importantly cephalofoil's existing components (DIP LED, 9V battery). What else?????

So far, you suggested to switch to AA or AAA or even CR2032, use more resistors, making 2 series of LED where he wanted to place 3 LED each eyes. Isn't that making this more complicated?

What I can see is that you are complicating things. If it towards better solution, I can live with that. But the fact it is not, people are not gaining from your post.

I am not a snob that saying all my ideas are always correct, but I have reasons and I am gladly explain it why my ideas is helpful to people (read: I can back it up). I always trying to keep it simple and cheap. As pre-wired LED is cheap, DIP LED + resistor is cheaper.