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How to Use 1W Star LED


These power LED stars offer an extremely high light output in an energy efficient way. The power LED comes mounted on to special PCB star that acts to draw heat away from the LED, therefore extending its operational life. This makes them perfect for many lighting applications and this sheet explains how.

Technical Information

Forward Voltage: 3.0V – 3.4V
Angle: 110 deg
Luminus Flux (lm): 110 – 130
Colour Temp: 2700K – 3300K


Mechanical Information



how_to_use_a_1w_warm_star_led_2 Description:
1W Warm white power LED star
Stock Code:


Using the LED

The LED is a 1W LED and the forward voltage is rated at 3.0V to 3.4V so for the purpose of the calculations a forward voltage of 3.2V is used. The typical current of the LED will therefore be 310mA (from Power = Current x Voltage). The power source used with the LED must therefore be able to deliver at least 310mA. Since most power supplies will be higher than 3.2V a current limit resistor will be required. The next page shows a few examples of using this LED with different power supplies and what value this resistor needs to be. The resistor also needs to handle 310mA flowing through it and as a result will need to be a power resistor. Please note that during use both the star LED and the resistor will get hot and shouldn’t be touched.

The LED has markings for ‘+’ and ‘-’ as indicated below:


Single LED powered by a 12V wall block

how_to_use_a_1w_warm_star_led_4 Parts List:
12V wall block PSU
1W star LED
33 Ohm power resistor


Single LED powered by a USB lead

how_to_use_a_1w_warm_star_led_5 Parts List:
USB Power Cable (1m)
1W star LED
10 Ohm power resistor


Three LEDs powered by a 12V wall block

how_to_use_a_1w_warm_star_led_6 Parts List:
12V wall block PSU
1W star LED
10 Ohm power resistor


PLEASE NOTE: The resistor values (and power rating) listed have been calculated for the specific configurations demonstrated in this datasheet. If you make any alterations to the configurations listed, you must ensure that you use a suitably rated resistor of the correct value.


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19 thoughts on “How to Use 1W Star LED”

  • Sujay Singha September 28, 2014 at 7:39 am

    how make 5w led light in 12v dc

    • Rob Haywood September 29, 2014 at 10:10 am

      Hi Sujay,

      We only sell this LED in 1W and 3W versions.


  • Rob January 11, 2015 at 7:29 am

    I want to string a few LED in series. With 'regular' bulbs you look at the voltage drop off. Let's say it's 2.5V. If you have 120V you can put 48 of those bulbs in series without needing a resistor (120V/2.5V = 48). Now assume we have a 24VDC PSU. If a 1W LED has a forward current of 3.2V then I should put 8 in series (24V/3.2V) to get maximum brightness without putting too much current through them.

    Having said that, I read that LED need constant current. So would the above setup of a 24VDC PSU with 8 1W bulbs in series be a bad idea (shortened life, flickering, etc)?

    • Rob Haywood January 12, 2015 at 10:34 am

      Hi Rob,
      It should be fine to do that, the current will be constant with that setup.

    • David Hodgson June 22, 2017 at 9:27 pm

      2.5 years ago I converted my halogen bulb reading lamp to LED bulbs. I connected 3x 1W LED Stars in series and attached them to an aluminium backing plate with heat conducting tape. I used a Femtobuck 350mA constant current supply to drive the LEDs. It worked perfectly but recently started to flicker. Cooling the backing plate with water restored perfect operation. It appears therefore that the LEDs have degraded over 2.5 years. I rebuilt the assembly with three new LEDs and adhesive tape and it works fine again, thereby confirming that the old LEDs had become defective.
      Is 2.5 years all I can hope for, or should I be using an extra heatsink?

      • Mark Donnison June 23, 2017 at 10:08 am

        Hi David, it is difficult to say without some rigorous testing but heat can greatly reduce the lifespan of LEDs. I would say that it is highly likely that any steps you can take to reduce the amount of heat that the LEDs are subjected to would have a noticeable effect on their lifespan.

        • David Hodgson June 23, 2017 at 6:21 pm

          Thank you Mark for your helpful comment. I've added a heatsink to my new design and crossed my fingers. Sadly the datasheet says nothing about lifetime. Amazingly this same LED can be run at twice the current, i.e. 700mA. I shudder to think how long it would last in that case.

  • sarabjeet March 31, 2015 at 7:01 pm

    i want to use 10 nos. of 1w led bulbs in parallel me to make this circuit with component values

    • Rob Haywood April 1, 2015 at 12:59 pm

      The easiest way to do this would be to use one resistor per LED, however you will need a power supply which can handle at least 3.1 Amps, you would normally therefore use a 5A PSU.


  • Marcelo May 26, 2016 at 6:44 am

    Hi. I want to use three 1W LED in serise in 110V. It's possible using a polyester capacitor to drop the voltage?

    • Mark Donnison May 26, 2016 at 11:43 am

      Hi Marcelo, thanks for getting in touch. Each of the LED's would nominally drop the voltage around 3.5V, as you have them in series this would add up to a total of 10.5V. This would leave you with approx. 100V's still to lose. We would suggest using a 12V regulated supply for your circuit, if possible, rather than use a capacitor.

      I hope this helps.

      • Marcelo May 27, 2016 at 8:19 am

        Well, it's that I would like to mount to a E27 socket bulb.

  • Clay December 7, 2016 at 11:25 am

    Hi,I want to have 3 groups ,with each group having 3 1w led in parallel and then put each group in series, and still use 12v psu woulfd this be possible.Also would i need resister ?..

    • Rob Haywood December 8, 2016 at 2:28 pm

      Hi Clay,

      The forward voltage of the LEDs is 3.0-3.4V so it would not be possible to power 9 of these from a 12V supply.


  • Vishal Thombare December 24, 2016 at 5:38 am


    Thanks for sharing this article , this is very easy to understand and helpful.

    I am new to this . May be this question seems sily to you :).

    I bought 4 LEDs of 1 w and connected 12v - 2 amp power supply to it. After powering ON, it glow once and then went OFF. I think it has damage.

    Is it because i gave higher voltage.?

    Your calculations says each LED required 3.2 v forward does that mean i have to connect 4 LED in series to work this circuit perfectly with 12v 2 amp driver.

    What if i want to connect such 10 LEDs in series. What will be the power requirement. ?
    I have 230 v 400 AMP power supply . What type of registors i have to use to control power output.


    • Rob Haywood January 11, 2017 at 9:24 am

      Hi Vishal,

      The PSU you used has too much current.
      Likewise a 400 amp power supply is certainly too powerful. The LEDs only draw 310mA.


      • Vishal Thombare April 9, 2017 at 11:12 am

        Thanks Rob for your response .

  • Sherwin Baptista January 17, 2017 at 10:43 am

    I have 5pcs of 1W LED and want to connect it to a single power source of 12V 7Ah lead-acid battery,
    My question:
    If i connect all leds in parallel my total current requirement will be 1.55A at 3.4V, so what value and wattage resistor should i use with the above mentioned power source?

    • Rob Haywood February 6, 2017 at 8:25 am


      Each LED would need a 33Ohm power resistor. The resistors would need to be connected to each LED in series.


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