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Habibu Bello Abubakar
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Join Date: Feb 2013
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LED as a DC Bulbs

02/19/2013 9:52 AM

How can I used LED as a 12 V. DC Bulb
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lyn
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#1

Re: LED AS A DC BULBS

02/19/2013 9:56 AM

Just feed it 500mA DC power at 2.5-3.5 volts.
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SolarEagle
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#2

Re: LED AS A DC BULBS

02/19/2013 10:11 AM

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Yahlasit
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#3

Re: LED AS A DC BULBS

02/19/2013 10:22 AM

Use a series resistor, calculate it using this formula:

R= (V supply - V LED)/LED current

If your led has a forward voltage of 3.6 V, your power supply is 12 V and the nominal current of the LED is 500mA (which is fairly high, found only on modern high light output LEDs), then it should be:

R= (12-3.6)/0.500 = 16.8 ohms

You can use a broad range of voltages and resistor values, only make sure you don't exced the nominal LED current.

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NotUrOrdinaryJoe
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#4

Re: Led as a DC Bulbs

02/19/2013 12:03 PM

It really depends on which LED you select. The average LED only uses 20 mA not the half amp that was suggested previously.

There are several suppliers who provide LED replacement bulbs for existing sockets. Sometimes, however, the bulb is too big to fit the fixture.

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redfred
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#5

Re: Led as a DC Bulbs

02/19/2013 12:23 PM

The least efficient but simplest method is to just provide a series resistance to handle the voltage drop from 12V to the diode voltage at the desired current. One of the most efficient approaches would be to design a switch mode power supply that outputs a constant current into the LED. A SMPS can be designed to handle a wide input voltage range so a failing 12V battery will produce the amount of light. With circuit miniaturization a SMPS can be incorporated into the base of many light bulbs.

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gmphadte
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#6

Re: LED as a DC Bulbs

02/20/2013 12:53 AM

Use LM 317T and make a constant current source of the desired mA.

Gajanan Phadte
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PWSlack
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#7

Re: LED as a DC Bulbs

12/10/2020 2:35 AM

Just buy one.

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JRaef
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#9
In reply to #7

Re: LED as a DC Bulbs

12/11/2020 4:29 PM

7 years later, I think it is no longer an issue for the OP...

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SolarEagle
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#8

Re: LED as a DC Bulbs

12/10/2020 4:53 AM

For a single LED you need a 330 Ohm 1/2 watt resistor in the circuit...

For 3 LEDs in parallel you need 100 Ohm 1 watt resistor...

For 3 LED's in series....47 Ohms 1/4 watt...

...Or you can just use a current limiter...

https://lighthouseleds.com/20ma-led-current-limiter-driver.html?gclid=CjwKCAiAq8f-BRBtEiwAGr3DgSh9G17sIL2G_OzliSZf6Benm1nv2sjmeq4FlSfs_fkI7-WApOn9KhoCeFkQAvD_BwE

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gmphadte (1); JRaef (1); lyn (1); NotUrOrdinaryJoe (1); PWSlack (1); redfred (1); SolarEagle (2); Yahlasit (1)

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