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I'm building a project to flash three concentric rings of LEDs in sequence to give the effect of light moving from the centre to the edge. The circumference of each loop is based on an even number of LED blocks (three LEDs per block @50 mm), so the three strips will be:

Strip 1    610 mm   12 blocks     36 LEDs
Strip 2   1400 mm   28 blocks     84 LEDs
Strip 3   2050 mm   41 blocks    123 LEDs

What I figured out so far is that I can use an Arduino Nano to control the pattern, and a MOSFET to turn each strip on and off with the right timings.

I came unstuck looking at power and voltage specifications for the MOSFET, then saw diagrams using other components in the circuit and am completely out of my depth. How can I do this?

I'm planning on using white SMD5630 LED strips (60 LEDs/m) and have calculated the power/current for the largest strip (2050 mm, 41x3 LEDs) based on power information for this LED from How to select an appropriate transformer for 12 V LED strips as being 41 A/492 W, but maybe a grownup should check this.

I'm assuming I'll need three identical circuits, one for each strip.

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  • \$\begingroup\$ Add more information about the schematic. It is bit unclear for the middle and inner circle. \$\endgroup\$
    – Triak
    Commented Feb 19, 2015 at 23:06
  • \$\begingroup\$ 41A is not something you want to try to put through a wire if you are new to electronics. Break it into smaller pieces. \$\endgroup\$ Commented Feb 20, 2015 at 1:02
  • \$\begingroup\$ 2050mm, 41x3 leds? So 2 meters? That's 9.6 Watts. Not 492 Watts. \$\endgroup\$
    – Passerby
    Commented Feb 20, 2015 at 7:01
  • \$\begingroup\$ The circumference of each loop is based on an even number of LED blocks (three leds per block @ 50mm) so the three strips will be: *Strip 1 610mm 12 blocks 36 leds *Strip 2 1400mm 28 blocks 84 leds *Strip 3 2050mm 41 blocks 123 leds \$\endgroup\$ Commented Feb 20, 2015 at 10:26
  • \$\begingroup\$ I mistakenly specified the wrong chip It will be a SMD 5630 \$\endgroup\$ Commented Feb 20, 2015 at 10:28

1 Answer 1

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Per the specifications of the SMD3528: You apply 12 V to the strip. Each sub-group has three LEDs and a resistor.

The power calculation is given as: Total power = (0.08 W x LED_Quantity).
Or use 0.4 w x LED_Quantity for type SMD5630.

Using the total number of LEDs (LED_Quantity) calculate the total power, then divide by 12. This gives you required current (A).

So you will need a power supply with an output of 12 V at (A) ampere.

If you plan on flashing these strips with an Arduino output a good method would be to use a MOSFET in the DC line powering the LEDs. The MOSFET would need to be rated for at least 10 A. In place of a discrete MOSFET a similar rated solid-state DC relay module could be used. Solid-state relay modules often have opto-coupler inputs which are ideal for driving with an Arduino. If using a module be sure it is a DC type, not an AC type.

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  • \$\begingroup\$ Thanks for your answer. I spec'd the wrong chip. they will be SMD 5630's I used the first figures I found on interweb which look suspect. 0.5w per chip seems to be the number quoted in the data sheets. Am I correct in using this figure? \$\endgroup\$ Commented Feb 20, 2015 at 10:36
  • \$\begingroup\$ I don't see where you get 0.5w/LED. Looking on this page: ledlightsworld.com/page.html?id=38 , The chart shows: Strip Model 5630 300LED/Roll, 24w/100cm (1m). This comes to 24w/12v = 2A per meter. So with 60LEDs per meter, 24w/60LEDs = 0.4w/LED \$\endgroup\$
    – Nedd
    Commented Feb 25, 2015 at 3:51
  • \$\begingroup\$ With a 2050mm + 1400mm + 610mm = 4060mm, (4.060 meters), and 60 LEDs per meter: 4.060x60 = 244 LEDs. At 0.4w/LED: 244x0.4w = 97.6w. Using a 12v transformer this comes to 97.6w/12v = 8.13A . Since this is over 8 amps use the next larger transformer of 10 amp 120w. Transformers listed on this page: ledlightsworld.com/… \$\endgroup\$
    – Nedd
    Commented Feb 25, 2015 at 4:30
  • \$\begingroup\$ If you plan on flashing these strings with an Arduino output the best way would be by using a 10A mosfet or a similar rated Solid State DC relay module. Solid State relay modules often have opto-coupler inputs which would be ideal for driving with the Arduino. Be sure to get a DC module, not an AC type. \$\endgroup\$
    – Nedd
    Commented Feb 25, 2015 at 4:53

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