Yeah sorry the voltage source is 12V

 

So work some of those cases and see how large the variation in current ends up being.

 

I'd still like to "see" your intended layout or a picture of image you're making. This would give us a better idea of what kind of spacing you're looking at. Still need to know what LEDs you're thinking of: 3 or 5mm through-hole, surface mount, etc,? I'll ask one more time:


Is the following correct?

• You are limited or simply choosing to use a power supply rated at 12VDC at 4A, roughly 45W?
• All the LEDs are going to be mounted to a board that is 54" x 54"?

Now some questions:

1. Have you already selected or decided which LEDs you're going to use? If yes, please post links to these.
2. Will the LEDs be thru-hole such as 3mm or 5mm or SMD? There's also high power LEDs, but I don't think you'd be able to get that many on such a small area.
3. Is this display going to be viewed indoors or outdoors? If outdoors, will it be viewed in sunlight, at night, or both?
4. What is the closest distance someone will be viewing the display?
5. What is the farthest distance someone will be viewing the display?
6. Can you post a rough drawing or picture of the overall image you're trying to create with the LEDs? You don't need to draw hundreds of dots, just a line or shape will do.
7. Are you simply wanting to have the LEDs on or do you want to be able to make some or all blink and/or fade?
8. I'm curious how you got the current and wattage requirements for the LEDs. If I'm following correctly, it appears you've planned to connect three LEDs in series and parallel these sets. If so, then the red LEDs are getting 10mA each and the blue and white LEDs are getting 20mA each. Is this correct?
9. What material is the board going to be made from? 1/8" plastic, 1/4" plywood, etc.?
10. Will there be a cover over the display, e.g., glass, plastic, etc.?

 

Some of your strings show a 1 ohm resistor. You need to use one less LED in that string and increse the value of the resistor. I still maintain you can use 12V strips of LED's to accomplish what you want. It will save you work on mounting LED's, wiring them and such. If you want all the LED's to have the same intensity , or for the matter if you want them to have different intensities,reguardless of the wiring you can use PWM with each color. All LED's donot require 20 milliamps of forward current to produce the same intensity.

 

Right here is a picture that represents the depth of the project - note the tiles are more floor tiles than the sort of thing you would stick on a wall

 

This is the full extent of what the LED's are going to follow

 

This shows the through hole location of where the LED's are going to go - this will contain a lot of grout once I've got The tiling finished

 

This shows where I'm up to on the tiling so far

 

I'd still like to "see" your intended layout or a picture of image you're making. This would give us a better idea of what kind of spacing you're looking at. Still need to know what LEDs you're thinking of: 3 or 5mm through-hole, surface mount, etc,? I'll ask one more time:


Is the following correct?

• You are limited or simply choosing to use a power supply rated at 12VDC at 4A, roughly 45W?
• All the LEDs are going to be mounted to a board that is 54" x 54"?

Now some questions:

1. Have you already selected or decided which LEDs you're going to use? If yes, please post links to these.
2. Will the LEDs be thru-hole such as 3mm or 5mm or SMD? There's also high power LEDs, but I don't think you'd be able to get that many on such a small area.
3. Is this display going to be viewed indoors or outdoors? If outdoors, will it be viewed in sunlight, at night, or both?
4. What is the closest distance someone will be viewing the display?
5. What is the farthest distance someone will be viewing the display?
6. Can you post a rough drawing or picture of the overall image you're trying to create with the LEDs? You don't need to draw hundreds of dots, just a line or shape will do.
7. Are you simply wanting to have the LEDs on or do you want to be able to make some or all blink and/or fade?
8. I'm curious how you got the current and wattage requirements for the LEDs. If I'm following correctly, it appears you've planned to connect three LEDs in series and parallel these sets. If so, then the red LEDs are getting 10mA each and the blue and white LEDs are getting 20mA each. Is this correct?
9. What material is the board going to be made from? 1/8" plastic, 1/4" plywood, etc.?
10. Will there be a cover over the display, e.g., glass, plastic, etc.?

Hi _mech. Yeah the LED's are 5mm and will be through hole as opposed to surface mount. I've not bought anything yet apart from a few of the LED's so so far as the power source is concerned I'm not limited to anything. Ideally it would be a higher voltage supply than the 12V drivers that I've Been recommended to get. I'm guessing LED drivers are the only way to go as they convert to DC supply and regulate the current? I'm guessing 12V is also the best choice as any more and it would have serious implications for heat management and possibly melting wire??
Yes the board is 54"^2
The board is going to be for indoor use only ... To add the science that I'm proposing to it, I'm permanently tired at the moment as my job is working nights and I come back and struggle to sleep when the sun is coming up so it is going to go as a pair of mechanical shutters across my window which will open at a set time every day and flood my room with sunlight and help me to wake up

It's basically in my room so it will be a set distance from my bed of approx 4m and the LED's will not be blinking or fading. It's worthy to note that once switched on they probably won't be on for much more than an hour or two at the most but I guess in terms of heat and stress on the component they will get to optimum use within a few minutes??

No there is no cover to go over the top of it although I am considering spraying it with a shiny varnish to finish it.

So far as the wattage requirements I used this calculator:
http://led.linear1.org/led.wiz

And the Red LED's have the following spec sheets:
http://www.vishay.com/docs/83055/tlur540.pdf
... Or at least it should be I'm guessing TLUR 5400 is the product code, I grout them off eBay and the guy couldn't give me anymore relevant detail unfortunately so the red should conduct 20mA as the rest of them do

The rest of the LED's are:
http://www.ebay.co.uk/itm/5mm-Clear...346&pid=100015&prg=1006&rk=1&sd=140863518386&

And the white ones:
http://www.ebay.co.uk/itm/50-x-Ultr...Night_Lights_Fairy_Lights&hash=item58a1b6851a

And the red ones:
http://www.ebay.co.uk/itm/380658366219?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

 

Some of your strings show a 1 ohm resistor. You need to use one less LED in that string and increse the value of the resistor. I still maintain you can use 12V strips of LED's to accomplish what you want. It will save you work on mounting LED's, wiring them and such. If you want all the LED's to have the same intensity , or for the matter if you want them to have different intensities,reguardless of the wiring you can use PWM with each color. All LED's donot require 20 milliamps of forward current to produce the same intensity.

Hiya buddy - if you look at the images I have enclosed and seen how the project is constructed, its not possible unfortunately. Yeah that's not such a bad idea reducing the LED's. 1ohm of resistance Is important not to overlook that though? I asked earlier on if it's such that the only reason they include the value of 1 is so the equations don't equate to 0. If I didn't put a 1 ohm resistor in there would be trouhble??

 

Getting a better schematic together along with some specs on the LEDs will help a lot. Other points to consider clarifying:

1) Explain where your power/current numbers came from. It's not at all obvious and strangers that are asked for help are far more likely to help if you don't make them guess or reverse engineer your thoughts using a crystal ball.

To try to answer some of your questions:

If you use a 12V voltage source with a 4A rating, then it can supply UP TO 4A while holding the voltage at 12V (which would be 48W, not 45W, but that's in the ballpark). Each circuit that is connected across the supply will draw whatever current it will draw at 12V. As long as the sum of all such currents does not exceed 4A, then each circuit is independent and won't even know the other circuits are there (i.e., connecting/disconnecting one should have no significant impact on the others).



I'm not picturing what you have in mind. 52x3=156, so what is up with the 157th LED?

As long as you use sufficiently large wire to connect the brnaches to the string, the voltage drop along the string can be as small as you want. How long, physically, will the longest string be?

WBahn thank you for your inputs:
Well 156 3 in a series and one on its own in the series 3 branches of.
So are you saying basically the larger the wire the better? I'm guessing the strings will possibly reach a maximum length of a meter on the longest white branches.
The power output figures are basically off a website where I've been looking at drivers to power the LED's just seeing what the cheapest option is out there

 

Oh yeah and elec_mech the ply (well actually its chipboard to be 100% accurate is a 1/2 thick

 

I asked earlier on if it's such that the only reason they include the value of 1 is so the equations don't equate to 0. If I didn't put a 1 ohm resistor in there would be trouhble??

And I addressed this point.

What is the current, I, in the string with 6 LEDs?

I = (Vs - 6Vd)/R

Now, plug in the following values:

A) Vs = 12V, Vd=2V, R=1Ω
B) Vs = 12.5V, Vd=1.8V, R=1Ω
C) Vs = 12V, Vd=1.8V, R=1Ω
D) Vs = 12V, Vd=2.2V, R=1Ω
E) Vs = 12V, Vd=2V, R=1.1Ω
F) Vs = 12.5V, Vd=1.8V, R=0.9Ω
G) Vs = 12V, Vd=1.8V, R=1.1Ω
H) Vs = 12V, Vd=2.2V, R=0.9Ω

If you would take the time to crank the numbers on a few of the scenarios I spelled out, you will see that using a 1Ω resistor is completely unsatisfactory. The smaller the resistor, the less unstable the current.

Case D won't result in any current at all, regardless of what size the resistor is.

Case F will result in nearly two amps of current instead of 20 milliamps - or 100 times what you want.

 

I'm guessing LED drivers are the only way to go as they convert to DC supply and regulate the current?

If you don't need to flash, dim, etc. the LEDs, then all you need are resistors and a DC power supply. This can be what we often call a wall wart, although you may need something a little bigger to provide enough current. It isn't a driver so much as power supply that converts your AC wall power to DC power.

I'm guessing 12V is also the best choice as any more and it would have serious implications for heat management and possibly melting wire??

It's worthy to note that once switched on they probably won't be on for much more than an hour or two at the most but I guess in terms of heat and stress on the component they will get to optimum use within a few minutes??

Not quite - unless you select a tiny wire or put all of this into small box with zero air flow, I don't think overheating is going to be a concern with this project.

I was a little confused by your explanation. So is this being hung on a wall like a picture frame or being used as shutters?

Okay, 5mm LEDs it is. With a half (inch?) of wood plus tile, the base will be robust but thick. This will make it a little challenging to mount the LEDs. Typically one drills a hole big enough to allow the LED dome through but small enough to allow the LED lip to catch or uses an LED holder. In both cases, this only works for material about 1/8 inch thick. In your case, you'll need larger holes to allow the whole LED to pass through then seal it somehow, perhaps with caulk. Another concern is being sure the LED is oriented straight (perpendicular to the surface) as the caulk sets or however you decide to fasten them.

The white and blue LEDs you've selected will be extremely bright - like looking into a flashlight bright. If this was for an outdoor application and viewed from tens of meters away or more, then they'd be fine. Since this is for an indoor application with a short viewing distance, I'd strongly suggest looking at diffused LEDs for the white and blue like the red ones you've selected. Something like this and this. Look for a rating of about 100mcd. Anything in the 1000s will be blinding.

Also note the blue and white LEDs will probably still be brighter than the red, so you may find you want to either increase the current to the red LEDs by selecting lower valued resistors or dim the blue and white by using higher valued resistors to increase or decrease the current, respectively.

Other members have already said it, but I'll say it again - six red LEDs in series will not work at 12VDC. The reason is the forward voltage to a red LED is ~2V. Six in series requires 12V minimum. In layman terms, you need at least another volt or two to spare to allow a resistor to properly limit the current going to the LED. WBahn has tried to point this out to you mathematically. You'll need to put five LEDs in series or use a power supply with a higher voltage than 12VDC. There should be no reason not to wire five in series as opposed to six - you can always run wire longer distances if needed to put the LEDs where you need to. I'll work on the power requirements when time allows to see if your proposed 12VDC, 4A supply will be able to provide enough power.

No there is no cover to go over the top of it although I am considering spraying it with a shiny varnish to finish it.

This may affect the LEDs appearance (light output, not so much physical appearance). If you opt to use a varnish, I suggest you apply it before installing the LEDs so they stay varnish free.

 

And I addressed this point.



If you would take the time to crank the numbers on a few of the scenarios I spelled out, you will see that using a 1Ω resistor is completely unsatisfactory. The smaller the resistor, the less unstable the current.

Case D won't result in any current at all, regardless of what size the resistor is.

Case F will result in nearly two amps of current instead of 20 milliamps - or 100 times what you want.

Ah sorry for missing that one dude. Point taken so I basically need to reduce the LED's till I can find a resistor which will balance the current to a satisfactory level

 

If you don't need to flash, dim, etc. the LEDs, then all you need are resistors and a DC power supply. This can be what we often call a wall wart, although you may need something a little bigger to provide enough current. It isn't a driver so much as power supply that converts your AC wall power to DC power.





Not quite - unless you select a tiny wire or put all of this into small box with zero air flow, I don't think overheating is going to be a concern with this project.

I was a little confused by your explanation. So is this being hung on a wall like a picture frame or being used as shutters?

Okay, 5mm LEDs it is. With a half (inch?) of wood plus tile, the base will be robust but thick. This will make it a little challenging to mount the LEDs. Typically one drills a hole big enough to allow the LED dome through but small enough to allow the LED lip to catch or uses an LED holder. In both cases, this only works for material about 1/8 inch thick. In your case, you'll need larger holes to allow the whole LED to pass through then seal it somehow, perhaps with caulk. Another concern is being sure the LED is oriented straight (perpendicular to the surface) as the caulk sets or however you decide to fasten them.

The white and blue LEDs you've selected will be extremely bright - like looking into a flashlight bright. If this was for an outdoor application and viewed from tens of meters away or more, then they'd be fine. Since this is for an indoor application with a short viewing distance, I'd strongly suggest looking at diffused LEDs for the white and blue like the red ones you've selected. Something like this and this. Look for a rating of about 100mcd. Anything in the 1000s will be blinding.

Also note the blue and white LEDs will probably still be brighter than the red, so you may find you want to either increase the current to the red LEDs by selecting lower valued resistors or dim the blue and white by using higher valued resistors to increase or decrease the current, respectively.

Other members have already said it, but I'll say it again - six red LEDs in series will not work at 12VDC. The reason is the forward voltage to a red LED is ~2V. Six in series requires 12V minimum. In layman terms, you need at least another volt or two to spare to allow a resistor to properly limit the current going to the LED. WBahn has tried to point this out to you mathematically. You'll need to put five LEDs in series or use a power supply with a higher voltage than 12VDC. There should be no reason not to wire five in series as opposed to six - you can always run wire longer distances if needed to put the LEDs where you need to. I'll work on the power requirements when time allows to see if your proposed 12VDC, 4A supply will be able to provide enough power.



This may affect the LEDs appearance (light output, not so much physical appearance). If you opt to use a varnish, I suggest you apply it before installing the LEDs so they stay varnish free.

Ahh cool maybe I will consider that then I take it there's no issues with current regulation then and power surges etc? They will go across the window and then slide open ... I'm planning on a device which will automatically open it at 11am each day

I've been musing all day over how to get the LED's to sit straight in the holes and here's the plan so far:
The holes have been slightly filled with tile adhesive and because some of the surrounding tiles are very small I daren't try enlarging the holes with a drill as it may pull it out so ...
Buy some smaller dowels (4mm) coat them in butter, put them in the holes to do the grouting (butter so they come out easily without creating a raised bit of grout)
Once dried, firstly cut in half, then drill all holes from the back forwards to get perfectly perpendicular holes with a 5mm bit
Then follow it through with either a 5.5mm or 6mm bit that I put a mark on to show where a distance 6mm less than the width of the project is and drill so it has the two diffent bores.

I kinda figured its not mega important to have the wider bore super accurate (in terms of depth inwards) so long as the LED has its dome suspended at some point by a 5mm bore.

By doing it this way, ill make the area surrounding the hole stronger through the grouting, then when re-boring the holes it hopefully won't have a lot of resistance to clear away a bit of grout. Also by slightly filling the existing holes a little more with the grout (due to using smaller dowels to fill them) it will allow me to get the LED's perpendicular.

What you think??

Ahhh shucks I've already brought the LED's :-( so am I right in saying that if I reduce the current they will dim?? Only I read somewhere if you reduce either current or voltage they simply won't work at all . Upon thinking about the science of it I'm guessing reduced voltage will prevent them from working yeah?

 

Oh yeah and just to raise the point again everyone, with having the different colour circuits coming directly from the power source, does this mean that the more peripheral circuits will suffer a difference in current? I know that the point has been raised that so long a you use large enough wire it will not draw too much current and voltage off it, but all I can think is if say, I have the red LED circuit with 33 LED's branching off the central wire that lead to the power source, then the wires travel another 10" to meet one of the white LED circuits, then the red circuit will receive more power ... Do the same rules apply to this set up as they do to parallel circuits? I.e having circuits tapping into a central power source

 

I do not think wire size is much of a problem, # 20 wire has about 1 Ω per 98 ft.

 

Sounds like you have a plan for fixing the LEDs in place. I'd suggest testing your ideas on some scrap material first to be sure.

If the LEDs are going to stick out, i.e., the base will rest on the surface, you could drill smaller holes - just enough to allow the leads to pass through but not the base. Even if they aren't perfectly perpendicular, you should be able to adjust them a little by hand depending on how you fasten the leads.

If not, you may consider looking for some metal tubing often found in model shops. If you can find a tube that an LED can fit snuggly into, you could drill the hole sized to fit the tube and use the tube to place the LEDs. Once the LEDs are adhered to the panel, the tubes could be removed.

You could also cut the tube into small lengths - just enough to act as spacer to increase the LED O.D. to snuggly fit the hole diameter - then dab a drop or two of CA glue to keep the LED and tube bonded. Just some thoughts.

Ahhh shucks I've already brought the LED's :-( so am I right in saying that if I reduce the current they will dim?? Only I read somewhere if you reduce either current or voltage they simply won't work at all . Upon thinking about the science of it I'm guessing reduced voltage will prevent them from working yeah?

You can dim them some by reducing the current by increasing the resistor value. This will only go so far and the white and blue are still going to far outshine the red. You can diffuse them yourself by sanding the LED. It will still be bright, but perhaps not blindingly so. Give it a shot with a couple of spare LEDs first and see if you get the results you want. Be sure to test all three colors together so you can "see" how bright they are relative to one another.

 

Hiya buddy - if you look at the images I have enclosed and seen how the project is constructed, its not possible unfortunately. Yeah that's not such a bad idea reducing the LED's. 1ohm of resistance Is important not to overlook that though? I asked earlier on if it's such that the only reason they include the value of 1 is so the equations don't equate to 0. If I didn't put a 1 ohm resistor in there would be trouhble??

The 1 ohm would be useless as it will have little if any on limiting the current limit which is important for LED's. Another point, the intensity of LED's varies and to achieve the same amout of light with less LED's is accomplished with fewer LED's at a higher MCD.