LED sequencing/supplies

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Postby gyre » Mon Oct 04, 2010 12:44 am

Some of those color changing strings come addressable and with some default programs.


LEDs come from 1.2 V to 7.5 V.

I still don't understand why not use parallel LEDs and regulate the voltage at the output.
Far more efficient.
And dimmable with the right output, like pwm.
No need to burn out those tricolor LEDs

Running series requires a faith in chinese production standards I lack.
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Postby Theres Always One » Mon Oct 04, 2010 7:06 pm

I guess I am still a bit confused. So the LED wizard is basically telling me to break my LED's up into small groups of LED's wired in series with a resistor on it. The group + resistor stays under the total voltage of the power source (like you said jungle smacks). Then all those mini series are wired together. I kind of see what is going on how this would work instead of having one long 120 LED string wired in parallel. But if I have 13 (or however many it is) of these groups isn't that still going to be 13x times the draw than the source can handle? Or is that what the resistor is for?

Image

I guess I still don't understand how this makes it okay to have such a huge draw on a small power source. Will this rid me of my overheating issues or do I just need to beef up the power supply?

Edit: And don't mind that it says 24v instead of 12. I was just trying it out to see what it would do. It looks like it keeps giving me the same kind of setup regardless of configuration of quantity LED, forward voltage, or power source.

Thanks for your help. :)
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Postby gyre » Tue Oct 05, 2010 12:07 am

13 times the load is 13 times the load.

If you aren't using excessive power on the LEDs, your only improvement is to eliminate or minimize the resistor size.

Are you going to match the LED required voltage as closely as possible with the batteries?
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Postby junglesmacks » Tue Oct 05, 2010 1:24 am

gyre wrote:13 times the load is 13 times the load.

If you aren't using excessive power on the LEDs, your only improvement is to eliminate or minimize the resistor size.

Are you going to match the LED required voltage as closely as possible with the batteries?


Wait.. stop. This is bad advice. Too late now to explain volts vs amps and all that fun stuff. There is a reason for it all explain later. The schematic is right for a reason.
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Postby gyre » Tue Oct 05, 2010 5:09 am

If the battery pack can be closer to native LED voltage and less series nonsense, very worth it.


Another choice is a regulated power supply.

What is your pack?
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Postby junglesmacks » Tue Oct 05, 2010 8:44 am

gyre wrote:13 times the load is 13 times the load.


It's not 13 times the load. It's matched exactly to the supply voltage. Now, how many mA it's drawing is another issue. Your battery source and how many mA it is will dictate how long you can run the string. Different battery types have different mA ratings. 8 x AAs, or a 12v lantern battery, etc etc.

gyre wrote:If you aren't using excessive power on the LEDs, your only improvement is to eliminate or minimize the resistor size.


Depending on the LED of course, for a standard 5mm LED you can really only vary around 5-10mA. You can run them less, but be careful running them more. One option to improve battery life is to increase the resistor value for the series string as to run them all at say 15ma instead of 20ma. Some super brights that want 30ma you can run at 20ma and be fine. Again though, careful overloading them. You may burn them out.

gyre wrote:Are you going to match the LED required voltage as closely as possible with the batteries?


This is the intent of the series strings. You are matching the total draw of the string to the battery output. The resistors purpose is not to control voltage, but to regulate flow and give each LED the correct mA value. For example.. if you had a 12v output and were running red LEDs that consumed say.. 2v. You would be matching the battery output by connecting 6 in a row. 2v LED + 2v LED + 2v LED + 2v LED + 2v LED +2v LED = 12v total power draw.
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Postby gyre » Tue Oct 05, 2010 8:48 am

13 strings = 13 x 1 string's load.
Don't know why voltage is relevant here.


Without matching voltage, the series is used, maybe for no reason.
Very much to be avoided.

What is the pack voltage?
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Postby junglesmacks » Tue Oct 05, 2010 8:55 am

gyre wrote:13 strings = 13 x 1 string's load.
Don't know why voltage is relevant here.


Without matching voltage, the series is used, maybe for no reason.
Very much to be avoided.

What is the pack voltage?


Voltage is completely relevant, and you are matching the voltage by using the connections of strings with the correct amount of LEDS per string. Remember how electrical connections work when you are using parallel vs series connections. In a series circuit , the current through each of the components is the same, and the voltage across the components is the sum of the voltages across each component. In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component.

Meaning.. that you are part right. 13 series strings connected in parallel is still only drawing 12v, but is drawing the same amount of current as if they were all together.

Remember the difference between voltage and current. Here is a great page that explains it: http://www.kpsec.freeuk.com/voltage.htm
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Postby gyre » Tue Oct 05, 2010 8:57 am

Why is the pack voltage locked?
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Postby junglesmacks » Tue Oct 05, 2010 9:09 am

gyre wrote:Why is the pack voltage locked?


Because of the type of battery being used. Batteries have set voltyages that they output. They will output less and less as they get drained, but never more.

AA, C, D battery = 1.5v each

When you series them together, the voltage output adds together.. just as in that previous explanation. So, if you put 8 AA batteries together.. you get a 12v output.

Here is a wiki page on battery types: http://en.wikipedia.org/wiki/List_of_battery_sizes

Now, different battery types even if they are rated the same in voltage, will have a different mAh (milli amp hour) rating. Meaning.. how much juice is inside them that will be able to power a certain draw off them. This is what dictates for example how long you would be able to run a certain string.

For example, if you took this schematic that guy posted before it says that the total array draws 325mA. If you wanted this to run for say.. 6 hours, you would need a battery setup with a total mAh rating of (6x325) or better.

Think of say.. the difference between the battery in your car which is 12v, and 8 AA batteries together which is also 12v. Same amount of voltage output, but current is a whole other story..
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Postby gyre » Tue Oct 05, 2010 10:03 am

Why is the pack 8 batteries?
There is a choice.
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Postby junglesmacks » Tue Oct 05, 2010 10:34 am

gyre wrote:Why is the pack 8 batteries?
There is a choice.


Yes there is a choice. You can use a 2 battery pack, a 4, 8, whatever you want. I keep using an 8 battery/12v example because it provides a good amount of power in a compact space. If weight/size us an issue, by all means use less. Use down to a disc battery if you want. The project I'm working on has 240 LEDs involved, so I need some juice to run all that.
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Postby gyre » Tue Oct 05, 2010 10:42 am

Doesn't have to be even numbers either.

If you need juice, no reason not to run parallel batteries in D cell.
That is only an issue with rechargeable batteries in larger sizes.
Not so much with disposables.
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Postby junglesmacks » Tue Oct 05, 2010 12:05 pm

True.. just most battery packs come in even numbers. Most.

Also, 8 D cells would be pretty encumbersome to wear in a costume. You would also have them in series, not parallel..
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Postby Theres Always One » Tue Oct 05, 2010 10:19 pm

Ok junglesmacks,

I think I like that pic board you posted earlier. Then with the NPN Transistor you can run more than one LED per channel.

junglesmacks wrote:
http://picprojects.org.uk/projects/ledc ... m#Firmware

This gives a basic trigger signal to 8 LEDs. The plan is to use NPN power transistors to use those trigger signals to trigger a string of 24 LEDs on each of the 8 channels. So yeah, the board runs off of 12v.. and then each string is jumped by the same 12v source via transistors.


I'm planning on doing something very similar to you (I think). I want to have the board cycle through each channel and each channel will be a different color. This will mean that each one will need its own set of transistors because the different colors will have different forward voltages. Is it possible to run, say, 6 red LED's and and 6 green on the same channel? That LED wizard link you posted earlier.....I can't find it right now.....does that calculate based on different LED's on the same line?


junglesmacks wrote:DOH!

Of course, now after I've spent $60 on parts and supplies, I find someone with exactly what I'm trying to build. FML.

http://www.digitallighting.com/animatio ... /bcser.htm

I just spoke with these guys, and they said that they supply to a number of Burning man art cars. Check em out and maybe do something cool for next year.. :wink:


Although I want this as much as you do. But $90? Come on. Pricey. I like your idea about the PIC board with the NPN transistor.

.....I think I need a bit more research and I will come back.
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Postby junglesmacks » Tue Oct 05, 2010 10:24 pm

Actually I picked that board up for $60 on EBay. ( http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWAX:IT - make an offer for $60 and it will be automatically accepted) I mean, all the mosfets are prewired and it's fused and it's plug and play and perfect. I went for it. Now, I do also have 2 of the other kits that I bought as well. What I like about those is that they aren't just chase sequences, but full on different light patterns. Check that YouTube video. So, I'm going to play with building them and seeing what happens.

Yes, you can run multiple colors off of the same channel. What you would do, is make a series string of just that color and then parallel it in with the other string. For example.. say you had a 12v source, and you wanted to run 10 red LEDs and 10 green LEDs off of the same channel. You would make 2 strings of 5 red LEDs (assuming they want 2v forward voltage) and then 4 strings of green LEDS ( assuming say a 3.3v forward volatage, 3 x 3 LEDs on ones and then 1 x 1 LED on another). Parallel those into the channel, and they are both taking the 12v.

Yeah.. my plan is to run a different color off of each channel.. going through the rainbow spectrum. I've actually got red, orange, yellow, green, aqua, purple, pink and white. I'm running 24 of each color LEDs off of each channel, and having the colors go in sequential rings down my pants.

I'm thinking now of wiring the pants up and then having just an input plug for the whole pants wiring. Then, keeping the circuit board and battery in a compartment in my backpack, and having an output plug for that. Only drawback is not being able to take my backpack off too easy. Hm. We will see how this all pans out. It's happening though.. :twisted:
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Postby Theres Always One » Wed Oct 06, 2010 12:31 pm

junglesmacks wrote:Yes, you can run multiple colors off of the same channel. What you would do, is make a series string of just that color and then parallel it in with the other string. For example.. say you had a 12v source, and you wanted to run 10 red LEDs and 10 green LEDs off of the same channel. You would make 2 strings of 5 red LEDs (assuming they want 2v forward voltage) and then 4 strings of green LEDS ( assuming say a 3.3v forward volatage, 3 x 3 LEDs on ones and then 1 x 1 LED on another). Parallel those into the channel, and they are both taking the 12v.


I am going to be running a seperate channel for each color as well. Same as yours I believe.

But I was thinking about this last night and I guess I am still not understanding how the voltage and number of LED's works. Even looking at the diagrams by the wizard I still don't get it.

The sum of the forward voltages must not exceed the voltage of the power supply.

So... 1 purple LED with a forward voltage of 3.6v needs a 3.6v power supply. 6 LED's = 6 x 3.6 = 21.6v power supply?! What am I not seeing here? Because you are talking about running 10 red off one 12 power supply.

And I was thinking of...after I figure out what the optimum quantity of LED's to run per channel.....I would be happy with 12 but if I could get 18 or 24 I would be even happier....can I use the LED wizard for each LED color to find the corresponding resistor?

So if channel 1 is orange with a 3.5v forward voltage I would use this setup for channel 1.

Image

Then if channel 2 is red with a 2.2 forward voltage I would use this setup for channel 2?

Image
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Postby junglesmacks » Wed Oct 06, 2010 1:57 pm

Theres Always One wrote:
junglesmacks wrote:Yes, you can run multiple colors off of the same channel. What you would do, is make a series string of just that color and then parallel it in with the other string. For example.. say you had a 12v source, and you wanted to run 10 red LEDs and 10 green LEDs off of the same channel. You would make 2 strings of 5 red LEDs (assuming they want 2v forward voltage) and then 4 strings of green LEDS ( assuming say a 3.3v forward volatage, 3 x 3 LEDs on ones and then 1 x 1 LED on another). Parallel those into the channel, and they are both taking the 12v.



The sum of the forward voltages must not exceed the voltage of the power supply.

So... 1 purple LED with a forward voltage of 3.6v needs a 3.6v power supply. 6 LED's = 6 x 3.6 = 21.6v power supply?! What am I not seeing here? Because you are talking about running 10 red off one 12 power supply.



Yes.. if you wanted to run 6 of those purple LEDs in a series, you would need at least a 21.6v power supply. That's why if you were running say a 12v power supply, you would use them in strings of 3 connected in a series, and then parallel those all together. Use that wiring schematic generator to test it out.

I was using 10 red LEDs with a forward voltage of 2v-2.2v as an example. If you were using a 12 volt source, you would run 2 series strings of 5 LEDS each, and them parallel them to the battery. That way, they battery would still only see no more than 12v of draw. Each string of 5 LEDs would be 2v + 2v + 2v + 2v + 2v = 10v.

You've got this.. :D


By the way.. not sure how you are planning on running 18-24v from your battery pack? I mean.. you could put 2 - 9 volt transistor batteries in series and that would give you 18v.. true. Just wouldn't have much mAh with those two little guys.
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Postby Theres Always One » Wed Oct 06, 2010 5:11 pm

junglesmacks wrote:
Theres Always One wrote:
junglesmacks wrote:Yes, you can run multiple colors off of the same channel. What you would do, is make a series string of just that color and then parallel it in with the other string. For example.. say you had a 12v source, and you wanted to run 10 red LEDs and 10 green LEDs off of the same channel. You would make 2 strings of 5 red LEDs (assuming they want 2v forward voltage) and then 4 strings of green LEDS ( assuming say a 3.3v forward volatage, 3 x 3 LEDs on ones and then 1 x 1 LED on another). Parallel those into the channel, and they are both taking the 12v.



The sum of the forward voltages must not exceed the voltage of the power supply.

So... 1 purple LED with a forward voltage of 3.6v needs a 3.6v power supply. 6 LED's = 6 x 3.6 = 21.6v power supply?! What am I not seeing here? Because you are talking about running 10 red off one 12 power supply.



Yes.. if you wanted to run 6 of those purple LEDs in a series, you would need at least a 21.6v power supply. That's why if you were running say a 12v power supply, you would use them in strings of 3 connected in a series, and then parallel those all together. Use that wiring schematic generator to test it out.

I was using 10 red LEDs with a forward voltage of 2v-2.2v as an example. If you were using a 12 volt source, you would run 2 series strings of 5 LEDS each, and them parallel them to the battery. That way, they battery would still only see no more than 12v of draw. Each string of 5 LEDs would be 2v + 2v + 2v + 2v + 2v = 10v.

You've got this.. :D


By the way.. not sure how you are planning on running 18-24v from your battery pack? I mean.. you could put 2 - 9 volt transistor batteries in series and that would give you 18v.. true. Just wouldn't have much mAh with those two little guys.



I was just testing the wizard out. That pic board can only handle 9-12v anyways. So I am thinking that i would go 12v via 8x AA batteries? I don't know. This needs to be ultra portable and on-the-go like your pants. Energizer makes some awesome AA's that have a really high aH but are also like $10 for a 4 pack.

I guess next is to figure out the amperage. I'm sure with AA's and such I will probably be getting like .5aH lol. Who says LED's are efficient? 20mA per light? I have 12" compact flourescent lights that are 1,000,000 times brighter and only draw 5 mA.
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Postby Theres Always One » Thu Oct 07, 2010 9:19 pm

Ugh. I just ordered most of my LED's. They are all in the 20-25 mA range and the orange is 30 mA.

Then I'm reading this document to figure out the NPN transistor and it is talking about how these LED's require something beyond what an NPN transistor is capable of and it should not be used with these LED's.

http://picprojects.org.uk/projects/inf/drivingLEDs.pdf

I think I'm going to cancel the order for now and see if I can find LED's that use less mA. Or I don't know. Am I worried over nothing?

The document seems to be based off the assumption that LED's are going to be drawing 15 mA. But, from what I've seen, pretty much everything out there is "super high bright" and in the 20-30 mA range.
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Postby gyre » Thu Oct 07, 2010 9:30 pm

When talking about ma, the voltage matters.

20 ma is pretty typical for a low voltage LED.

I think a AA is at least 3 amp/hours.


The lithium one use strength is their stable voltage and exceedingly light weight.
They have a substantial amount of power too.
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Postby junglesmacks » Thu Oct 07, 2010 9:53 pm

Theres Always One wrote:Ugh. I just ordered most of my LED's. They are all in the 20-25 mA range and the orange is 30 mA.

Then I'm reading this document to figure out the NPN transistor and it is talking about how these LED's require something beyond what an NPN transistor is capable of and it should not be used with these LED's.

http://picprojects.org.uk/projects/inf/drivingLEDs.pdf

I think I'm going to cancel the order for now and see if I can find LED's that use less mA. Or I don't know. Am I worried over nothing?

The document seems to be based off the assumption that LED's are going to be drawing 15 mA. But, from what I've seen, pretty much everything out there is "super high bright" and in the 20-30 mA range.



All LEDs except the super brights should be 20 mA. Where are you getting them from? I picked up a bunch from Ebay super duper cheap.. and they are awesome. Tested them all and they kick butt. Do some Ebay searching.

Here is a link to the orange ones that I bought 25 for $1.50 with free shipping: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWNX:IT

There are all colors available.. just search.

In a conversation with Pete who created that pic board and website that you are quoting, he said that you don't have to run the LEDs at the stated mA requirement. You can get away with running 20 mA LEDs at 15, and the 30 mA "superbrights" at 20 mA if you are concerned with battery power.

You would also want to run either all super bight 30 mA models or the normal 20 mA models or else some will be brighter than others.

ALSO.. I was advised to use MOSFETs, not the NPN transistors die to the fact that they have higher power handling and dissipate less power. Use a MOSFET.
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Postby Theres Always One » Thu Oct 07, 2010 10:05 pm

junglesmacks wrote:
All LEDs except the super brights should be 20 mA. Where are you getting them from? I picked up a bunch from Ebay super duper cheap.. and they are awesome. Tested them all and they kick butt. Do some Ebay searching.

Here is a link to the orange ones that I bought 25 for $1.50 with free shipping: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWNX:IT

There are all colors available.. just search.

In a conversation with Pete who created that pic board and website that you are quoting, he said that you don't have to run the LEDs at the stated mA requirement. You can get away with running 20 mA LEDs at 15, and the 30 mA "superbrights" at 20 mA if you are concerned with battery power.

You would also want to run either all super bight 30 mA models or the normal 20 mA models or else some will be brighter than others.

ALSO.. I was advised to use MOSFETs, not the NPN transistors die to the fact that they have higher power handling and dissipate less power. Use a MOSFET.


I got my LED's from Niktronix. http://www.niktronixonline.com/5mm_LED_ ... owslow.htm

18 cents per LED seemed reasonable to me. I know its cheaper on ebay but I've looked around eBay but I have issues with some people's eBay webpages. They have way too much information and it confuses me to the point that I'm not always sure what I am getting. Plus I don't always want to spend $30 for 1000 LEDs. The way I figure, I'm just done with it and I don't have to spend alot of time searching eBay for that deal. But, in retrospect...yeah those are some screaming good deals and I'm a fool for paying way too much for my LEDs. Ah when will I learn?

Thanks for the advice on the MOFSET. I'm off to learn what a MOFSET is and what I will need and where I can get it. :)
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Postby gyre » Thu Oct 07, 2010 10:08 pm

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Postby junglesmacks » Thu Oct 07, 2010 10:14 pm

These guys are a great source for electrical components: http://www.allelectronics.com/

MOSFETs are pretty simple things, really. 3 pins. You hook one pin up to (+), one to (-). When the middle pin gets juice, it flips the switch and completes the circuit. It's just a simple relay.
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Postby Theres Always One » Thu Oct 07, 2010 10:14 pm



Yes. Maxiumum Complication!!! :evil:
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Postby junglesmacks » Thu Oct 07, 2010 10:18 pm

Theres Always One wrote:I got my LED's from Niktronix. http://www.niktronixonline.com/5mm_LED_ ... owslow.htm



Ooooo whoa... notice how on that site they have a whole discussion forum on LED lighting mods.. I would venture to guess that a good amount of info could be drawn from there too.. :wink:
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Postby Theres Always One » Thu Oct 07, 2010 10:24 pm

junglesmacks wrote:These guys are a great source for electrical components: http://www.allelectronics.com/

MOSFETs are pretty simple things, really. 3 pins. You hook one pin up to (+), one to (-). When the middle pin gets juice, it flips the switch and completes the circuit. It's just a simple relay.


Ok......

My understanding of the NPN Transistor was that it would create a gain in the current flowing from the PIC to the LED's based on my needs and which transistor I chose.

Does the MOFSET work the same way?

I'll check out allelectronics. I used to use Mouser when I was building a Sound and Light Machine. I didnt realize what they had until they randomly sent me their catalog in the mail and it was bigger than the phone book. I'll check out allelectronics though.
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Postby gyre » Thu Oct 07, 2010 10:35 pm

I like the ultra efficient relays for most things, but transistors have their place for cost and speed in rapid switching.


I've used these guys and I think diamond electronics too.

http://www.carlton-bates.com/
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Postby Theres Always One » Thu Oct 07, 2010 10:40 pm

I do believe we want enhancement MOFSETs. I found this:

There are two ways in which a MOSFET can function. The first is known as depletion mode . When there is no voltage on the gate, the channel exhibits its maximum conductance . As the voltage on the gate increases (either positively or negatively, depending on whether the channel is made of P-type or N-type semiconductor material), the channel conductivity decreases. The second way in which a MOSFET can operate is called enhancement mode . When there is no voltage on the gate, there is in effect no channel, and the device does not conduct. A channel is produced by the application of a voltage to the gate. The greater the gate voltage, the better the device conducts.
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