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What is the best way to light 10 POWER-LEDs with AC mains (220V)?

(I want to make an LED lamp.)


Here is more info:

I have 10 of these POWER-LEDs:

1W POWER LED

  • Product Chip: 40x40 mil
  • Chip Brand: EVERLIGHT-Taiwan
  • Lumens: 90-100LM
  • Voltage: 3.2-3.4V
  • Current: 300-350mA
  • Viewing angle: 140 degrees

And I have soldered all of them in series (with heat sink).

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    \$\begingroup\$ Yes, you can, but that would be a very bad idea for safety. \$\endgroup\$ Aug 13, 2014 at 10:19
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    \$\begingroup\$ Welcome to this community. Unfortunately there is not enough information to give you an answer and you question may be closed quickly because of this. Please edit your question and add more information about your exact LED model for instance. \$\endgroup\$
    – Blup1980
    Aug 13, 2014 at 10:20
  • \$\begingroup\$ Dear Vladimir Cravero. It will be a lamp. A light bulb. and cannot be touched . So there is no reason to be worried about its safety. \$\endgroup\$
    – AHB
    Aug 13, 2014 at 12:23
  • \$\begingroup\$ @BlueSky When dealing with AC mains, safety is always a factor. Don't take AC mains lightly. \$\endgroup\$
    – Funkyguy
    Aug 13, 2014 at 13:13
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    \$\begingroup\$ My English is not well ('it cant be touched' means nobody will touch the tracks on the PCB). I thought you have realized it ! You say that it's dangerous? So I'll never use Capacitive Power Supplies . Now I edited my question . please read it if you want. \$\endgroup\$
    – AHB
    Aug 13, 2014 at 16:42

1 Answer 1

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Ten in series will require 32V-34VDC at 300-350mA, or worst case just about 12W. You'll need a stepdown transformer from 240VAC to 36VAC at 350mA, and you'll need a half-wave rectifier (do NOT use a full-wave rectifier unless you use a 24V transformer!) good for 50V @ 350mA, and you'll need one stabilizing power resistor capable of dropping about 2V at 350mA (about 5.7 ohms), rated for 12W.

I mentioned a full-wave rectifier. You COULD use a full bridge rectifier with a 24VAC transformer secondary - that'd get you 24*1.414!=34V, but then you wouldn't have any room for the stabilizing power resistor so you'd be running on blind faith unless you removed ONE of those LEDs from the circuit and replaced it with an equivalent power resistor.

Do remember... this whole assembly will generate a significant amount of heat, and you have to get rid of that heat somehow or you'll overheat the LEDs and the resistor.

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  • \$\begingroup\$ No capacitors needed? I'll use a 24VAC transformer and 9 LEDs. then how much resistance should the stabilizer resistor have ? \$\endgroup\$
    – AHB
    Aug 14, 2014 at 4:56
  • \$\begingroup\$ Tthe stabilizer resistor should have about 87.5 Ohms. So Is this schematic the answer ?? \$\endgroup\$
    – AHB
    Aug 14, 2014 at 5:09
  • \$\begingroup\$ Nearly. It'll need a stepdown transformer between the 240VAC and the bridge rectifier, though. \$\endgroup\$ Aug 14, 2014 at 11:05
  • \$\begingroup\$ Yes, I forgot to add transformer in schematic. \$\endgroup\$
    – AHB
    Aug 14, 2014 at 11:15

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