who here knows about batteries and electronics?

[RedShoe]

If a D-cell battery and a AAA battery are the same voltage. Then why would you need to ever use a D-cell?

I need just 9 volts to power some LED's (maybe less but it seems to work well with a 9 volt) Would 6 AA's be the same thing? The problem with a 9 volt is the size. I have no way to mount a 9 volt. I DO have a way to mount 6 AA's, but they add way too much weight, and are actually too big for the project.

I know inside 9 volt is 6 AAA's. Would I be able to mount 6 AAA's in place of the 9 volt?

I need 3 volts to power an LED. I was told I'd need 3 volts per LED. So the way I understood it. if I have 2 LEDs I'd need 6 volts. 3 LED's = 9 volts. I ended up using 40 LEDs, but that would mean I'd need 120 VOLTS????

I can power 40 LEDs with a 9 volt with no problem. I haven't even tried less voltage.

The guy at the electronic store said I'd need 12 volts to power 40 LEDs.

This electronic shit is confusing.

[Babaganoosh]

It's all about current (measured in amps).

[Tempest]

There's 2 different things that you have to consider... voltage and current (amps). 9V batteries are just that, 9Vs.. AA, AAA, D, C etc. are all 1.5 Volts. So to make 9V you need to connect 6 1.5 volt batteries in "series", i.e. plus to negative ends so you get 1.5 + 1.5 + 1.5 + 1.5 + 1.5 + 1.5 = 9

If your LED needs 3 volts, then you can't use a 9V or you'll fry them.. UNLESS you use a resistor in between the battery and the LEDs in order to reduce the voltage the LED will actually "see".

To power a 3V LED, you would connect 2 AA in series to get the 3Volts. Now here's the thing. Each LED will require a certain amount of current in order to glow, not just the 3volts. So if you hook up a bunch of LEDs (in parallel), they'll all require 3volts but they'll draw even more current than a single LED, and thus drain your batteries a hell of a lot faster. So in this case you'd want to connect more batteries in "parallel" in order to supply more power.

AA, AAA, C, D - all 1.5 volts and just different sizes that have come about over time. Also, although I haven't checked, the larger batteries can probably supply more current than the smaller ones.

[stickyfingerz]

as said above Amperage is the key. Its easier to understand in terms of a water analogy. Voltage is kind of the size of the pipe, and amperage is the pressure of the water flowing through the pipe... if that makes sense.

[jeffrey]

err.... first off, I do not understand how you could have room for 6AA's but not a single 9v battery.

A d cell and a AAA are the same voltage but the D battery has more charge, so it will put out that voltage for much longer then the AAA.


Do you know how much resistance each LED is?
Even for 40 LEDs if they are the small ones a 9v battery could fry them.

and are they mounted in parallel or a series?
series is one after the other in a row (like have the + of one led connect to the - of the next), parallel would be like having a positive and a negative wire and then bridging the leds across every 1cm or 10cm or whatever.

[Calvinguy]

And you never mount a LED directly to a power source. You need a resistor also, size of R (resistance) depends of I (current).

[jeffrey]

Originally Posted by Calvinguy

And you never mount a LED directly to a power source. You need a resistor also, size of R (resistance) depends of I (current).

and depends on voltage too.

V=IR
Where V is voltage, I is current and R is resistance. And to find resistance you need to know if its a series or a parallel curcuit, as resistances dont just add up.

there are some LEDs you could hook right to some batteries. But not most.

[RedShoe]

I got 40 LEDs and according to the guy at the electronics place ElectronicCity.com he did some quick math problem and figured I'd need a 12v power supply with like 240 ohm resistors? Or something.

Luckily I know how to wire them in a series based on a crude drawing I found online. He told me I'd need 2 then a resistor, and repeat that. So I did.

He even told me HOW to figure the resistor (don't ask me now, but he did show me.) I just glazed over and asked him to do the math for me. He did.

Now then, as far as the 9v vs 12v and the amount of room I have. The 6 AA's can wrap around the contour of the project better than a clunky 9v. Think like the chamber of a revolver gun. The AA'a would hug the contour like the bullet chambers of a revolver, whereas the 9v doesn't really "wrap around" very well.

[RedShoe]

I guess ultimately what I'm trying to do is learn more about voltage and amps so I can further streamline this project.

[Tempest]

Originally Posted by RedShoe

I got 40 LEDs and according to the guy at the electronics place ElectronicCity.com he did some quick math problem and figured I'd need a 12v power supply with like 240 ohm resistors? Or something.

Luckily I know how to wire them in a series based on a crude drawing I found online. He told me I'd need 2 then a resistor, and repeat that. So I did.

He even told me HOW to figure the resistor (don't ask me now, but he did show me.) I just glazed over and asked him to do the math for me. He did.

Now then, as far as the 9v vs 12v and the amount of room I have. The 6 AA's can wrap around the contour of the project better than a clunky 9v. Think like the chamber of a revolver gun. The AA'a would hug the contour like the bullet chambers of a revolver, whereas the 9v doesn't really "wrap around" very well.

Still not exactly sure what you need. Why do you need 40 LEDs and do you simply want them all to be ON? Do they need to all be conected in series? or in parallel?

Here's what I remember.. LEDs are basically diodes and diodes usually require 0.7Vs and LEDs needed about 10 milliamps to turn on.

So if you have a 3V battery (or 2 1.5V in series), you take 3V - 0.7V = 2.3V / 0.010 amps = 230 ohms.. Thus that's where the 240 Ohm resistors come from (I don't think you can get 230 so you'd use 240).

Are you only powering the LEDs with this? Cause you could just use a single 1.5V battery and 80ohm resistors to do the job.

Like most things, there's multiple solutions to a problem, it all depends on what you're trying to do. That would determine whether you'd connect them all in parallel, series or some combination of that. And that configuration will dictate how many batteries you need and what resistors etc.

For example. You could connect all the LEDs in series with a 240 ohm resistor, but that would require a (40 * 0.7V) + (240 * 0.01) = 28 + 2.4V = 30.4V power supply.

If you connected them all in parallel, it would require 0.01 * 40 = 0.4 amps and only a 1.5V battery and an 80 ohm resistor, but that 0.4amps will drain a single battery very quickly.

[RedShoe]

It's for my light thing. When I get back out to the office I'll post a pic for you.

[PHP-CODER-FOR-HIRE]

Dude... stop fucking around with the resistance of the circuit, and use incandescent bulbs instead of LEDs. Sure, LEDs use a lot less power, and sure they the latest thing, but normal bulbs are fine for most purposes, and are easier to use... Plus you get sockets for bulbs that make it real easy to replace them... Go the your local radioshack and get a 1.5/3/6/9/12v 1A wall adapter and wire it into your circuit.. Then do the same with cigarette adaptor.

Radioscrap also sells external battery enclosures and project casings.

Either no more batteries, or easy to use enclosure.

[Vick!]

jeez! What a load of crap concepts about electricity.


RedShoe, Listen me:

First, you don't need 120 volts to turn 40 LEDs ON. OK?


Second, what I have understood from your question is you want to turn on 40 LEDs and have only 9 volts power source.

Best thing you can do is, connect 3 LEDs in series and make one circuit .. Similarly, make 12 more circuits each consisting of 3 LEDs.

OK, you have 13 circuits with 39 LEDs now. Connect all 'circuits' in parallel and then connect that to 9 volt source. The remaining one LED can be connected directly to 9 volt source via 1k ohm resister.

I am an Electronics Engineer, and I think my input should have weight.

Let me know if you want to reduce the weight of 9 volt source or need any other setup to make this shit work.

[Vick!]

Originally Posted by Tempest

Still not exactly sure what you need. Why do you need 40 LEDs and do you simply want them all to be ON? Do they need to all be conected in series? or in parallel?

Here's what I remember.. LEDs are basically diodes and diodes usually require 0.7Vs and LEDs needed about 10 milliamps to turn on.

So if you have a 3V battery (or 2 1.5V in series), you take 3V - 0.7V = 2.3V / 0.010 amps = 230 ohms.. Thus that's where the 240 Ohm resistors come from (I don't think you can get 230 so you'd use 240).

Are you only powering the LEDs with this? Cause you could just use a single 1.5V battery and 80ohm resistors to do the job.

Like most things, there's multiple solutions to a problem, it all depends on what you're trying to do. That would determine whether you'd connect them all in parallel, series or some combination of that. And that configuration will dictate how many batteries you need and what resistors etc.

For example. You could connect all the LEDs in series with a 240 ohm resistor, but that would require a (40 * 0.7V) + (240 * 0.01) = 28 + 2.4V = 30.4V power supply.

If you connected them all in parallel, it would require 0.01 * 40 = 0.4 amps and only a 1.5V battery and an 80 ohm resistor, but that 0.4amps will drain a single battery very quickly.

OMG

[Stephen McTowelie]

Hi

Have you looked into lith-ion or lith-polymer batteries (mobiloe phone batts)they're extremly small and lightweight and available at quite resonable prices on ebay etc.
although they're not cheap compared to normal AAA's.

[Vick!]

Originally Posted by Stephen McTowelie

Hi

Have you looked into lith-ion or lith-polymer batteries (mobiloe phone batts)they're extremly small and lightweight and available at quite resonable prices on ebay etc.
although they're not cheap compared to normal AAA's.

At last, someone with reasonable solution.

[rowan]

Originally Posted by Tempest

Still not exactly sure what you need. Why do you need 40 LEDs and do you simply want them all to be ON? Do they need to all be conected in series? or in parallel?

Here's what I remember.. LEDs are basically diodes and diodes usually require 0.7Vs and LEDs needed about 10 milliamps to turn on.

LEDs are diodes but they don't have the same forward voltage as say, a rectifier or silicon diode. A typical forward voltage for a basic opaque red LED is 1.8V, green is slightly higher at about 2.0V, and white goes higher still, up past 3.5V. That's why many LED torches use 3 x 1.5V cells, to avoid the need for circuitry to step up the voltage.

[Vick!]

Originally Posted by rowan

LEDs are diodes but they don't have the same forward voltage as say, a rectifier or silicon diode. A typical forward voltage for a basic opaque red LED is 1.8V, green is slightly higher at about 2.0V, and white goes higher still, up past 3.5V. That's why many LED torches use 3 x 1.5V cells, to avoid the need for circuitry to step up the voltage.

[Tempest]

Originally Posted by rowan

LEDs are diodes but they don't have the same forward voltage as say, a rectifier or silicon diode. A typical forward voltage for a basic opaque red LED is 1.8V, green is slightly higher at about 2.0V, and white goes higher still, up past 3.5V. That's why many LED torches use 3 x 1.5V cells, to avoid the need for circuitry to step up the voltage.

As I said, it was "from what I remember"... I haven't worked with the specifics in over 10 years now so am a little rusty.

[RedShoe]

here is what I am doing with the LEDs and you'll see why a smaller power supply is better than a larger one.









AA's would wrap around the perimiter better. But they add too much weight.
The 9v is smaller in weight and footprint size, but it doesn't really mount very well to the project and is bulky looking. I have single and double mounting brackets for the AA'a. But they are simply too heavy and too long to really work.

[RedShoe]

As you can see by my crude electrical skills that I'm still new to this.

Vick, everything I read said to absolutely never put them in parallel.
You say put them in parallel, they say don't put them in parallel. LOL... This electrical shit is confusing.

I dig it though. I enjoy creating things. I seriously need this kind of creative outlet, but there is so much math and rules involved when it comes to this shit. I like creating, and I like lighting.

Lamps, I need to get into creating lamps. Is that a hobby? Are there others like me?

Now that I got it all wired up in a series and not in parallel, I wonder if it will work well.

[Tom_PM]

Go to radioshack or similar. They have lots of various odd shaped batteries and battery holders etc. You could use those 3v lithium watch batters. LED's dont need much current at all, and those batteries are super lightweight.

[Tom_PM]

I was going to make a deep water fishing lure. A flashing LED and 1 3v lithium battery worked perfect. I was going to mold it right into some soft plastic, like plastic mister twister lures melted down. Damn LED's need so little current, the thing blinked forever on 1 battery.

[RedShoe]

Originally Posted by stickyfingerz

as said above Amperage is the key. Its easier to understand in terms of a water analogy. Voltage is kind of the size of the pipe, and amperage is the pressure of the water flowing through the pipe... if that makes sense.

This actually makes perfect sense.

So you're saying I need a plumber, not an electrician?

[stickyfingerz]

Originally Posted by RedShoe

This actually makes perfect sense.

So you're saying I need a plumber, not an electrician?

Are you making a pass at me? I only swing that way for money.. just so you know.

[rowan]

Ouch... have you wired a single resistor for each LED? That's going to waste a shitload of power. If the forward voltage of the LED is 3.5V and your source is 9V then the resistor has 5.5V over it. If the current is 10 milliamps then the resistor is dissipating (wasting) 55 milliwatts per LED, with the LED itself consuming a further 35 milliwats. Multiply this by 40 and you're looking at some serious inefficiency.

Only 38% of the available power is used to light the LED, the rest is wasted...

[rowan]

Originally Posted by RedShoe

Vick, everything I read said to absolutely never put them in parallel.
You say put them in parallel, they say don't put them in parallel. LOL... This electrical shit is confusing.

What "they" meant was probably - don't put LEDs in parallel with a single dropping resistor. Each LED has a slightly different forward voltage so they'll end up "fighting."

You can put strings of LEDs in parallel if they each have their own dropping resistor.

Here's a quick diagram to demonstrate what I'm trying to say...



BTW, the resistor value has to be varied depending on the number of LEDs you have in the chain. Is your supply source 9V or 12V? Is it possible to mount the batteries on the camera somewhere and have a curly cord going to it?

[rowan]

Oh yeah, with regards to you using a 9V battery... if you're supplying 40 LEDs then it's unlikely it will last long. 40 LEDs at 10 milliamps each is a total draw of 400 milliamps (0.4A), and if you want more light you could probably go up to 30mA each which is 1.2A. I did a quick search and found a 9V rechargeable battery rated at 400 milliamp hours (0.4 amp hours), which means - in theory - it can supply 400 milliamps for an hour, 200 milliamps for two hours, 100 milliamps for four hours etc. Your 9V battery would probably provide useable output for less than 10-15 minutes, assuming it was even able to discharge at a 1.2A rate.

That's why D cells are bigger than AA; they have the same voltage, but they will last longer and/or provide a higher current.

[RedShoe]

Originally Posted by rowan

Oh yeah, with regards to you using a 9V battery... if you're supplying 40 LEDs then it's unlikely it will last long. 40 LEDs at 10 milliamps each is a total draw of 400 milliamps (0.4A), and if you want more light you could probably go up to 30mA each which is 1.2A. I did a quick search and found a 9V rechargeable battery rated at 400 milliamp hours (0.4 amp hours), which means - in theory - it can supply 400 milliamps for an hour, 200 milliamps for two hours, 100 milliamps for four hours etc. Your 9V battery would probably provide useable output for less than 10-15 minutes, assuming it was even able to discharge at a 1.2A rate.

That's why D cells are bigger than AA; they have the same voltage, but they will last longer and/or provide a higher current.

Rowan,

I did it the way you have in your 2nd drawing. I drilled 80 holes. I put in two LEDs, and soldered the + of on and the - of the other together. Then I soldered a resister to the end of the series of 2. I did that 20 times.



I hooked up a 9v and to see how long it would last I ran a test. (I didn't know the math so I did it the only way I knew how) I hooked up a 9v and just left it on. I checked it every 10 minutes for the first 2 hours, then popped in "The God's Must Be Crazy II" and it was still on and bright at the end of that movie. And the battery was cool to the tough. I was afraid I'd burn out the battery.
I dunno know why.. I just thought I would.

It's for a camera so I figured 2 hours should be more than enough to film. I can shoot a scene in just a couple of hours.

I think next I'll try to incorporate a rechargeable system so all you need to do is plug it in for a few hours before you shoot.

[tony286]

there was a time you could go to a radio shack and find someone there who could answer your question but thats no more.

[rowan]

Redshoe,

So much for theory, looks like it worked anyway. Which resistor value did you use? Are you happy with the light output?

[stickyfingerz]

Originally Posted by tony404

there was a time you could go to a radio shack and find someone there who could answer your question but thats no more.

haha I went the other day to get a dvi cable, and he hands me a hdmi cable. I laughed at him and walked away.

[woj]

v = i*r ....

[DWB]

Not gonna work without a Flux Capacitor

[jeffrey]

At least it works in practice, now lets see it mounted


I am trying to figure out how to use 140 LEDs that will plug into a standard light socket and give a good pattern of lighting.
But the 120v power source (AC at that) is really fucking with my math.

The more and more I play with electronics I think about becoming and electrician, although an electrical engineer would be better suited to answering these problems, lol

[Basic_man]

Originally Posted by RedShoe

Lamps, I need to get into creating lamps. Is that a hobby? Are there others like me?

You're not the only one. I'm building a LED grow lamp

[rowan]

Originally Posted by jeffrey

At least it works in practice, now lets see it mounted


I am trying to figure out how to use 140 LEDs that will plug into a standard light socket and give a good pattern of lighting.
But the 120v power source (AC at that) is really fucking with my math.

The more and more I play with electronics I think about becoming and electrician, although an electrical engineer would be better suited to answering these problems, lol

If I were you I would definitely avoid fiddling with mains until you know what you're doing. This is not just a throwaway line, I really do mean that. Your life or someone you love's life could depend on it.

[RedShoe]

Originally Posted by jeffrey

At least it works in practice, now lets see it mounted


I am trying to figure out how to use 140 LEDs that will plug into a standard light socket and give a good pattern of lighting.
But the 120v power source (AC at that) is really fucking with my math.

The more and more I play with electronics I think about becoming and electrician, although an electrical engineer would be better suited to answering these problems, lol

Here's the suck ass part. I built this for a crew that was going to Brazil. They use VX2000's. I have a DVX100B. They left a day earlier than they thought. So I never hooked up with them to drop it off. So now.. well... it's pretty much useless to me.


Here it is, I can just look at it and wonder if it works.






This looks like a video, but it's just a 2 frame animation.

[RedShoe]

Originally Posted by rowan

If I were you I would definitely avoid fiddling with mains until you know what you're doing. This is not just a throwaway line, I really do mean that. Your life or someone you love's life could depend on it.

I agree totally.
I have a Tron upright coin-op arcade. And when I got it I plugged it in and reached in the back to fiddle with the settings to get it to display properly. I looked for advice on a Tron board and found out how easily I could have been killed by touching one of the capacitors. Those things are fucking HUGE in those old uprights. And the one that could have killed me was just inchees from where I was fucking around. SCARED the shit out of me.

From now if it's more than 18 volts... I'm not fucking with it. And I mean like, an 18v battery operated drill. Not like car battery shit. I've seen 2 car batteries explode in my time. One was right in a guys face. I never fuck with car bateries now.

[rowan]

Originally Posted by RedShoe

Looks great, are you going to do a writeup for that one as well?

I wonder if this could be adapted for still use, providing some mild fill flash. From memory the high brightness LEs can be pulsed up to 100mA (or was it more)

Have you had any colour balance issues with your other light? As you can see, white LEDs put off quite a cold bluish colour.

[RedShoe]

Originally Posted by rowan

Looks great, are you going to do a writeup for that one as well?

I wonder if this could be adapted for still use, providing some mild fill flash. From memory the high brightness LEs can be pulsed up to 100mA (or was it more)

Have you had any colour balance issues with your other light? As you can see, white LEDs put off quite a cold bluish colour.

I don't know if I'll do a tutorial on this one as well.. but I certainly have enough photos of every stage of this one.

As far as the LED's being pulsed, I dunno. I just assumed you needed strobe/flash lights, I didn't know LED's could be used.

The color balancing will be tweaked when I find out how 'blue' it really is. Like I said this thing is just a $90.00 paper weight right now. I don't have a camera to test it on, hence all the photos are of it in my hand. LOL

[DWB]

Put a dimmer on it instead of a switch so you can control how much light comes out.

[RedShoe]

Originally Posted by DirtyWhiteBoy

Put a dimmer on it instead of a switch so you can control how much light comes out.

Stop telling me what to do all the time!
Oh so check this out, I go to the Electronis store. AndI've eben talked to a few guys here on GFY about this light thing as a direct result of this thread. They all agree that LEDs can NOT be dimmed.

"It's digital, it's either on or off, there is no dim"

I went to EVS today t pick up soame tapes and I saw one of their super-expensive panel lights which made up of about 200 LEDs. And, IT DIMS!

It's not a smooth dim, but it steps down in stages. Like maybe 10 steps from 100% down to 0%.

HOW IS THAT POSSIBLE???

[rowan]

LEDs can certainly be dimmed, just vary the current. That's why I asked earlier about the value of the resistor you used and whether you were satisfied with the light output.

Looks like you're using 240 ohms, which at 2 x 3.5V forward drop would work out to roughly 8mA of current. Check the specs to be sure, but it's likely the ones you have can tolerate more than double that. To limit the current to 20mA for the two LEDs in series with a 9V source you'd use a 100 ohm resistor.

To add dimming to your existing light just put a wire wound potentiometer in the "+" line between the battery and the array, say 1000 ohms. It needs to be wire wound (5 watts) because I don't think a standard pot would handle that current.

[rowan]

Oh yeah, some pots have an on/off switch built into them - when the pot is at minimum it clicks to off. Not sure if you can get them in wirewound, but that may help you save a bit of space.

[RedShoe]

Cool, thanks Rowan, I'm my way to ElectronicCity RIGHT NOW!

[RedShoe]

Well... shit. I just went to Electronic City and they said I'd fry a 1K potentiometer. So I showed him my post-it note (from Rowan's post) and he agreed I'd need a 5 watt potentiometer. He said he didn't carry anything that big.

Jeses, it must look like a dimmer switch from a wall outlet.

Either way... now I'm on a fucking mission. GET A DIMMER!!!
When he saw I had "40 whites" in the light he went "40 whites? WHOA!" LOL.

[Vick!]

RedShoe, Its hard to track the thread back and read lot of different opinions and so.

Why are you using 80 resisters? you know each resister would dissipate some power in form of heat and in turn will consume more battery?

You said you are using second method of rowan's drawing to connect LEDs, thats what I suggested.

But, when you connect 3-4 LEDs in series and attach to 9v battery you don't need the resister. The resister rowan showed is just because you are using two LEDs.

And I don't think anyone can say not to connect in parallel, whatever type of circuit it is. We always connect them parallel when we need to consume one source.
Just like, tube light, bulb and fan in your room are connected parallel to your main power supply.

Electronics is really very simple, you only need to learn 2-3 simple things.

* Ohm's Law
* Effect of series connected resisters and/or bulbs (LEDs whatever)
* Effect of parallel connected resisters and/or bulbs (LEDs whatever)

And the hobby you own is simply loveable. Why you are not into Engineering?

[Vick!]

I was suggesting this way:

[quantum-x]

Hey RedShoe, been watching your project with some interest. Nice one!

I know you're pretty much already done with your project, but if I may make a recommendation?

You might find that a few Luxor LEDs are what you're chasing. They go up to 5W [yes, 5W LEDs] - and their 3Ws are very bright, with a very reasonable power consumption [3AAAs will power them for 25+ hours on full bright]

Everyone is telling you different stories because there are definitely multiple ways to do these things.

Generally speaking though, hooking each LED [esp high consuptions ones such as the whites] to a battery is NOT the optimal solution - most SHOULD have a driver circuit to ensure steady current is delivered. If you can't control the current, you'll burn the LEDs out.

These will not only
a] prolong battery and LED life, but
b] provide maximum brightness off much smaller power supply

Links:
http://www.satcure-focus.com/tutor/page10.htm
http://www.luxeonstar.com/faq.php

Google for luxeon drivers or LED drivers, and you'll find plenty of people have gone where you have before.

I figure if you went to so much effort to make a great device, go the whole way! With a decet driver, you'll have dimming control, and a much cheaper and cleaner system.