Forget about resistors use a constant current source for the love of Christ.

 

How do you plan on repairing it when an LED or whatever breaks?

 

If the white LEDs are too bright & current can be cut down to 10 mA, then total current drain is down to 2A from 3.54A, not counting on blue changes. For interconnecting LEDs I would use # 28 bare tined wire with thin spaghetti as needed. for groups of strings, go to # 20, & maybe run two buss bars across bottom, or around perimeter of picture of # 18.
Is the big E about 4 in across?

 

Forget about resistors use a constant current source for the love of Christ.

Why? You would need to have a separate constant current source for each string of LEDs. Use a constant voltage source with multiple strings of LEDs with a current limiting resistor in each string. Pick the number of LEDs so that they drop about 3/4 of the voltage and drop the rest across the resistor. Put the same kinds of LEDs in each string so that their brightness will be reasonably close.

 

Hello!! The project is now finished and I am just in the process of working out power requirements and must ask this:

Basically the way it's connected is {series/parallel} within a parallel wire if that makes any sense. So I've worked out the resistance of each individual circuit and then worked it out as one individual parallel circuit as that made logical sense. However I am stuck at this:
The array produces
3.352 ohms of resistance through the LEDs and resistors
1.164 ohms for the 100' of 22 gauge wiring within it
... So how do I calculate the overall resistance?? Do you simply add the two numbers together or do you have to do:
1/[1/resistance of components + 1/resistance of wire] as in the case of parallel

Because in the latter case it basically reduces the resistance to less than an ohm which means that it would be drawing over 12A off a 5A source or if you add the numbers normally it draws 2.42A which is very comfortably within the parameters. There are 543LED's powered off the 5A 12V source so surely this is plenty right?
:S :S

 

And also I've switched it on for 30 mins seems to work perfectly well and after touching components they don't seem to be heating up at all ... Is this sufficient time for any components to blow up or over he's causing a fire risk?? They should according to many calculations and help off an Internet calculator all be resisted appropriately.

The power source has a 1A fuse at the plug and a 5A output so if it does start drawing too much current then the fuse should blow right??

 

LEDs are non-linear so it is not a simple matter of reducing things to equivalent resistances and adding them in series/parallel.

How many parallel strings do you have?

How much does each string draw?

Multiply the two numbers above and you have your total current draw.

If you have strings that draw different amounts, then group them according to current draw and add them up in groups.

543=181*3 and 181 is a prime number. How are these LEDs arranged?

 

Basically there is on strings:

124 - 14.6341463 ohms
118 - 15 ohms
39 - 46.1538462 ohms
1 - 600 ohms

All in blue

88 - 20 ohms
88 - 20 ohms
50 - 35.2941176 ohms

All in white

33 - 85.7142857 ohms

In red

Each one of these strings are connected in parallel to a central wire. Being as they all differ, are you saying add each of these values up to calculate the current draw when you say 'add them up in groups' ?? Once again many thanks for your help

 

Oh btw I've calculated this using ohms law from a current value given off an online calculator

 

Basically there is on strings:

124 - 14.6341463 ohms
118 - 15 ohms
39 - 46.1538462 ohms
1 - 600 ohms

All in blue

88 - 20 ohms
88 - 20 ohms
50 - 35.2941176 ohms

All in white

33 - 85.7142857 ohms

In red

Each one of these strings are connected in parallel to a central wire. Being as they all differ, are you saying add each of these values up to calculate the current draw when you say 'add them up in groups' ?? Once again many thanks for your help

I'm totally confused.

Let's take the last one. Are you saying you have one string of 33 red LEDs in series? That makes no sense if you are talking about a 5V supply.

Or do you have 33 strings each of which consists of 1 red LED and a resistor?

What is the value of that resistor? Is the 85.7Ω (and there no reason to report a resistance to nine significant figures!) the parallel equivalent of 33 resistors? How did you arrive at that 85.7Ω number?

Bottom line, what is your topology? Describe the circuit, not the results of what you've combined or did equivalents for, but the circuit as it actually is built.

 

My apologies:
Right ill start from the beginning - the driver gives the following output:
12V
5A

The red circuit is arranged as:
5 LED's connected in series which are attached to a 100 ohm resistor if I remember correctly (all series circuits regardless are resisted appropriately). this is then connected o parallel with the other 28 in the same configuration. the three remaining are also in series attached to a 330ohm resistor so this accounts for all of the reds.
Then the whites and blues are connected 3 and a resistor in series.

So the first number corresponds to the number in any given series/parallel array.

Each of these circuits is then attached in parallel to a central wire leading to the driver (I.e separate from the other circuits)

The values I've calculated are based on R = V/I with the voltage being 12V and the current is given by an online calculator

 

Just off the top of my head for example - I THINK it said 88 white in series/parallel draws 600mA so using ohms law 12 / 0.6 is 20 ohms.

... My original calculation of net resistance was formulated by getting values of resisttance for each series/parallel circuit and then running it as follows:

Lets say:
Resistance of 124 LED's is 'a'
Resistance of 78 LED's is 'b'
Resistance of 129 LED's is 'c'


Total resistance=
1/(1/a + 1/b + 1/c ... Etc)

 

Basically there is on strings:

124 - 14.6341463 ohms
118 - 15 ohms
39 - 46.1538462 ohms
1 - 600 ohms

All in blue

88 - 20 ohms
88 - 20 ohms
50 - 35.2941176 ohms

All in white

33 - 85.7142857 ohms

In red

Each one of these strings are connected in parallel to a central wire. Being as they all differ, are you saying add each of these values up to calculate the current draw when you say 'add them up in groups' ?? Once again many thanks for your help

I can't figure out how what you say above correlates in any way with what you say below:

My apologies:
Right ill start from the beginning - the driver gives the following output:
12V
5A

The red circuit is arranged as:
5 LED's connected in series which are attached to a 100 ohm resistor if I remember correctly (all series circuits regardless are resisted appropriately). this is then connected o parallel with the other 28 in the same configuration. the three remaining are also in series attached to a 330ohm resistor so this accounts for all of the reds.
Then the whites and blues are connected 3 and a resistor in series.

So the first number corresponds to the number in any given series/parallel array.

Each of these circuits is then attached in parallel to a central wire leading to the driver (I.e separate from the other circuits)

The values I've calculated are based on R = V/I with the voltage being 12V and the current is given by an online calculator

In the first post, for the red, you said

33 - 85.7142857 ohms

But in the second post you have 5 LEDs in a string and that you have a total of 29 such strings in parallel plus an additional string of three LEDs.

How does that relate to '33' in the first post?

Please describe the circuit for the blue and white in the same way that you did the red in the second post.

Then please give the forward voltage drop for a single red, white, and blue LED.

 

We can offer much more help if you could post a schematic similar to what you did in post #17, although I'd suggest using a different program like ExpressPCB which is made for drawing circuits.

As WBahn has mentioned, we're having a hard time following your descriptions alone. You're applying Ohm's Law and series and parallel resistances with the correct formulas, but I think you're missing the mark on how you're applying them or simply on how you're describing them, I'm not sure. In any event, please take some time and draw a schematic - if you're not 100% sure how you wired something or don't remember the exact value of the resistors you used, please check your circuit. It's extremely important to accurately document your work. For electronics, this is done with a schematic.

Once we have that we can verify if the power supply is adequate, if your resistor values are good, if the circuit is wired properly, and answer just about any questions you have. I cannot stress the importance of an accurate schematic enough. Without it, we're simply guessing what you've done which results in poor answers to your questions at best.

 

Oh btw I've calculated this using ohms law from a current value given off an online calculator

Those can't be trusted.
If your situation is exactly what the programmer imagined, they work very well, but they don't have the intuition to realize when you've made a mistake. Be sure to double check your answers.

 

Right guys and gals - I'm stopping out for work tonight so I am unable to draw up a full schematic. I have included an image of the layout of the circuits which will hopefully clarify the wiring. If its as feeble in use as it is in quality please let me know and ill do a more worthy one using a computer application.
Basically for each individual circuit I've calculated it's resistance so I can calculate an overall resistance using the formula:

Resistance = 1 / (1/a + 1/b + 1/c ..... Etc )

I hope it makes things a little clearer for you

 

Oh and the data is as follows:
Red LED:
2V
20mA

Blue LED:
3.1V
20mA

White:
3.3V
20mA

 

Just off the top of my head for example - I THINK it said 88 white in series/parallel draws 600mA so using ohms law 12 / 0.6 is 20 ohms.

... My original calculation of net resistance was formulated by getting values of resistance for each series/parallel circuit and then running it as follows:

Lets say:
Resistance of 124 LED's is 'a'
Resistance of 78 LED's is 'b'
Resistance of 129 LED's is 'c'


Total resistance=
1/(1/a + 1/b + 1/c ... Etc)

You are making extra work for yourself.
Once you have calculated the current draw for each series string (which will then be connected in parallel to the 12VDC supply), you just need to add the currents for your total required current. You don't need to re-calculate to come up with an equivalent resistance.

And as suggested, do your own calculations.

 

So literally if you have 3 LED's in series drawing 60mA then add this up for every colour and every string so if there's
170 strings of 3 in the configuration given and 6 strings of 5 LEDs then all I need to do is:
(170 x 60mA) + (6 x 100mA)
?!

 

Yes. Provided the LED strings (each string with a series resistor) are all calculated using the same power supply voltage, that's it. For the most accurate help, please post a detailed schematic of your intended setup.