How can I design an LED array that can be

[Bernard]

Hi All,

How can I design an LED array that can be driven effectively from my transformer?

Need some advise from you guru out here.

I'm thinking of replacing all my light blub to extra bright white LED but don't know how.

I'm totally know nothing about electronic stuff and hope that can get some advice here.

My 24VDC 5w light blub are connected in parallel and the power transformer is 24VDC 500mA. Is there any LED can take the load of my transformer?

Thanks,

Bernard

[nakazoru]

Dun think you can connect direct to the transformer. Anyway juz go to those LED shop at Sim Lim tower and they will advise you. They have a bunch of LEDs that is not restricted to 24V.

[cdckjn]

There are NO 24VDC LEDs, so no way to use current transformer. LEDs run on 6V okay, so better to buy proper LEDs from Sim Lim Tower. i bought a whole line of 30 LEDs (blue) with power supply at $22.

[Bernard]

Thank you guy's,

But the problem is that I have no way to pull out the wiring and redo the whole set up. So now have to make use of the set up.

I went down to sim lim tower few days ago and was told to use a high wattage 5w resistor with a 3 to 4.5v 10mm LED. when I first connected up everything seem fine. But half an hour later the LED just went out.

I went to this web site and the result I get is this.

http://led.linear1.org/led.wiz

24 Source voltage

3w diode forward voltage

20 diode forward current (mA)

1 number of LEDs in your array

Solution 0: 1 x 1 array uses 1 LEDs exactly

+24V R = 1200 ohms

The wizard says: In solution 0:

each 1200 ohm resistor dissipates 480 mW

the wizard says the color code for 1200 is brown red red

the wizard thinks 1W resistors are needed for your application

together, all resistors dissipate 480 mW

together, the diodes dissipate 60 mW

total power dissipated by the array is 540 mW

the array draws current of 20 mA from the source.

And now I have no idea what all the numbers above means.

[gunzo]

meaning you used too small a resistor

a Std LED runs 3.5v DC .. so if you want to run 24v transformer .. then you need to hookup 7 LEDs in series so they run a total of 24.5v or you run a combinatino of LEDs and resistors to achieve your 24vDC

what the wizard is telling you .. if you want to run 1 LED with a 24v transformer .. you need a 1.2k Ohm resistor running in series to bring the voltage down (ie V=IR) .. with a 1.2k resistor .. your wattage is 480mW (W=IV) .. so in order to safely dissipate 480mW of heat .. you need at least a 1W resistor (50% increase in tolerance)

I suggest you get the Luxeon series LED to get the lumens you want ..

Each LED is $15 .. kekekeke brightest in the market now ..

[chrisyew]

meaning you used too small a resistor

a Std LED runs 3.5v DC .. so if you want to run 24v transformer .. then you need to hookup 7 LEDs in series so they run a total of 24.5v or you run a combinatino of LEDs and resistors to achieve your 24vDC

what the wizard is telling you .. if you want to run 1 LED with a 24v transformer .. you need a 1.2k Ohm resistor running in series to bring the voltage down (ie V=IR) .. with a 1.2k resistor .. your wattage is 480mW (W=IV) .. so in order to safely dissipate 480mW of heat .. you need at least a 1W resistor (50% increase in tolerance)

I suggest you get the Luxeon series LED to get the lumens you want ..

Each LED is $15 .. kekekeke brightest in the market now ..

Output from the transformer is AC, you still need to convert the AC to DC before stepping down the voltages.

[Bernard]

what the wizard is telling you .. if you want to run 1 LED with a 24v transformer .. you need a 1.2k Ohm resistor running in series to bring the voltage down (ie V=IR) .. with a 1.2k resistor .. your wattage is 480mW (W=IV) .. so in order to safely dissipate 480mW of heat .. you need at least a 1W resistor (50% increase in tolerance)

$15 Just the LED going to cost me 300 over dollar?

ok btw. the confusing part is, it said it need 1.2k resistor and then 1w resistor again. So is that means I need to connect both 1.2k and 1w resistors to the LED or either 1 will do?

[Bernard]

Output from the transformer is AC, you still need to convert the AC to DC before stepping down the voltages.

Chim don't get it

my transformer is already out put at 24dcv.

[chrisyew]

Chim don't get it

my transformer is already out put at 24dcv.

Unless you are using those like handphone charger or built in AC to DC converter, else a normal step down transformer from 240V to 24V - the output is still AC and not DC.

Sim Lim sells a wide range of AC to DC converter and is not expensive. Probably best to get those AC 240V to 5V DC. You may connect the LED (5V types) directly in parallet to the output then. Those in Sim Lim selling 20 LEDs also do not have resistor connected in series with the LEDs, though it's better to have resistor.

In fact, juz buy these type and plug and play is the easiest.

Usually they have some simple rectifier circuit like this built in;

http://www.play-hookey.com/ac_theory/ps_rectifiers.html

[Bernard]

Unless you are using those like handphone charger or built in AC to DC converter, else a normal step down transformer from 240V to 24V - the output is still AC and not DC.

Sim Lim sells a wide range of AC to DC converter and is not expensive. Probably best to get those AC 240V to 5V DC. You may connect the LED (5V types) directly in parallet to the output then. Those in Sim Lim selling 20 LEDs also do not have resistor connected in series with the LEDs, though it's better to have resistor.

In fact, juz buy these type and plug and play is the easiest.

Usually they have some simple rectifier circuit like this built in;

http://www.play-hookey.com/ac_theory/ps_rectifiers.html

Thanks will check it out again.

[gunzo]

$15 Just the LED going to cost me 300 over dollar?

ok btw. the confusing part is, it said it need 1.2k resistor and then 1w resistor again. So is that means I need to connect both 1.2k and 1w resistors to the LED or either 1 will do?

luxeon is brightest now.. but cheapest led is still only around a few dollars a pack of 10

resistor is the value.. wattage is the heat capacity.. so you're looking for a 1.2k ohm 1watt resistor IF you intend to run only 1 led..

if you run 7 leds in series.. then no need resistor.. just make sure the +ve leg go to the -ve leg of the next led ..

[gunzo]

Unless you are using those like handphone charger or built in AC to DC converter, else a normal step down transformer from 240V to 24V - the output is still AC and not DC.

Sim Lim sells a wide range of AC to DC converter and is not expensive. Probably best to get those AC 240V to 5V DC. You may connect the LED (5V types) directly in parallet to the output then. Those in Sim Lim selling 20 LEDs also do not have resistor connected in series with the LEDs, though it's better to have resistor.

In fact, juz buy these type and plug and play is the easiest.

Usually they have some simple rectifier circuit like this built in;

http://www.play-hookey.com/ac_theory/ps_rectifiers.html

bro, he's misquoting it as a transformer.. think he's referring to a converter anyway.. don't be so pedantic and confuse him even more

std led only 3.5v.. so you still need resistor inline to lower the voltage..

those sold in simlim are wired in parallels of 3 units with 1 resistor..

becuz 3 =10.5v so you still need to buffer 1.5v using a 12vdc transformer

its not whether its better or not to use resistor..its just supply and demand..oversupply voltage then you lower the demand by putting in resistors

[chrisyew]

bro, he's misquoting it as a transformer.. think he's referring to a converter anyway.. don't be so pedantic and confuse him even more

std led only 3.5v.. so you still need resistor inline to lower the voltage..

those sold in simlim are wired in parallels of 3 units with 1 resistor..

becuz 3 =10.5v so you still need to buffer 1.5v using a 12vdc transformer

its not whether its better or not to use resistor..its just supply and demand..oversupply voltage then you lower the demand by putting in resistors

Think so he probably misquoted as transformer. Anyway it's not my intention to confuse him lah.

I've bought those with 20 leds connected directly to a 5V adapter (or converter) without resistors. The connection is in parallel. BTW there are already 5V leds and onli whether Sim Lim sell them - I don't know. Frankly the place is so much difference compared to 20 years + back when I was doing my project. Can't even find those shops that I juz to go hehe.

Think it's better to change his adapter or converter to probably a 5V one or better still one that suit the led. There are lots to choose from in SL.

[Bernard]

Thanks Bro's,

This is really a chim thing to knock head

The problem is that,

I need to use back the 24vDC/AC transformar to power up is because I can't even located where the transformar is So bopian have to use back lor.

[yus75]

wah tis ting looking interestin to diy....but im abit idiot in elec/electronic.......can some1 post a step by step w pic in doin tis.....

[Bernard]

wah tis ting looking interestin to diy....but im abit idiot in elec/electronic.......can some1 post a step by step w pic in doin tis.....

Try this one, have lot of info that I catch no ball

http://led.linear1.org/led.wiz

[gunzo]

quicky way as suggested by chrisyew also

1. go simlim tower 3rd floor

2. ask for led strip predone and converter package

3. pay $$ go home plug and play

expect about $22-28

[cci[RR]us]

Some things to note.

1. You may want to find some transparent blocks to disperse the light. The LED emission is highly focused and the "spotlight" feeling may not be pleasing to you.

2. You need to waterproof it. The legs of the LEDs may rust if they are exposed to salt sprays. That killed several of my LEDs.

3. Look for alternatives. Sometimes a simple FL might do the job well, at less cost and effort, but less hands-on fun as well.

I did my shitty LED here.

[Bernard]

us,Apr 27 2006, 02:50 PM] Some things to note.

1. You may want to find some transparent blocks to disperse the light. The LED emission is highly focused and the "spotlight" feeling may not be pleasing to you.

2. You need to waterproof it. The legs of the LEDs may rust if they are exposed to salt sprays. That killed several of my LEDs.

3. Look for alternatives. Sometimes a simple FL might do the job well, at less cost and effort, but less hands-on fun as well.

I did my shitty LED here.

transparent blocks where to get from and how it look like and how you waterproof it ?? Getting intresting and more headache