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I am planning to connect 100 LEDs to an arduino in a parallel circuit.

The current limit exceed beyond the Arduino UNO board.

In want to blink all 100 LEDs at same time. So how can I provide power source to 100 LEDs so they can blink with arduino programming.

Thanks in advance

Edit: As per discussion, MOSFET is required but which value MOSFET is required. There are many P- and N-channel MOSFETs available.

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    Arduino problem is only how to blink, not what to blink.
    – Juraj ♦
    Sep 16, 2018 at 10:07
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    A relay, a mosfet, a (motor) driver, a transistor, and so on. Have you soldered 100 leds parallel? That was a bad idea, they will not have the same brightness, since they require a certain current, not a voltage. What kind of leds are they?
    – Jot
    Sep 16, 2018 at 10:11
  • I little bit understand that Mosfet work as a switch of blinking function. What mosfet is better for lit 100 leds. i didn't connect 100 leds yet, but i will make circuit according to connectivity with arduino.
    – begin123
    Sep 17, 2018 at 7:35

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For 100 LEDs in parallel you will also need 100 resistors, and a transistor (MOSFET) that can handle the total current for all the LEDs.

For instance, at 20mA drive current you would be dealing with 2A - you'd need a (minimum) 2A power supply and a MOSFET that can handle 2A.

Or you can think a little differently.

If you use a higher voltage power supply you can group your LEDs together into chains. For example with a 12V power supply you could (depending on the voltage of the LEDs) have up to 4 in a chain (red LEDs, 2V forward voltage, 2x4=8. White LEDs, 3V forward voltage, 3x4=12). Each chain then has a single resistor, and you're working with a quarter of the current (500mA) - just 25 chains of 20mA but at a higher voltage. So you can use a smaller MOSFET and you have only 25 resistors.

Another thing you could consider is to then further group those chains together. Maybe 5 groups of 5 chains, each with their own MOSFET. Then you switch just one group on at a time, but cycle through them very rapidly. Each group only then uses 100mA (5 chains at 20mA = 100mA), and you can use a really small MOSFET, and your power supply needs only be able to provide a couple of hundred mA (give it some headroom) and can be smaller and cheaper.

The only down-side of that method is you can get flicker which may be noticeable if the LEDs are moving. It also means your Arduino is doing more work to light all the LEDs.

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  • Thanks for valuable reply. I also have 10 RGB Common Anode. in this project i want to make different animations,effects. I am studying about mutiplexing. Is it necessary to use TLC5940NT IC for multiplexing?
    – begin123
    Sep 17, 2018 at 7:38
  • No, you don't need the TLC5940NT. That doesn't multiplex, anyway, it's a shift register. For simple multiplexing of 10 LEDs you want 10 P-channel FETs and 3 resistors. Or you can use 5 P-fets and 6 N-fets and 6 resistors, depending on how you want to arrange your multiplexing. If you only want to use low currents then you could probably get away without the fets - as long as the total curret through an IO pin at any moment in time doesn't exceed 25mA (or 40mA for brief periods).
    – Majenko ♦
    Sep 17, 2018 at 9:08
  • ok could you please tell me the correct values for both p-channel FETS and 3 resistors and 5 p-fets and 6 n-fets, 6 resistors............................I little bit understand that Mosfet work as a switch of blinking function. What mosfet is better for lit 100 leds. i didn't connect 100 leds yet, but i will make circuit according to connectivity with arduino..........If you can share some tutorials, i will be very thankful to you.
    – begin123
    Sep 17, 2018 at 9:32
  • A MOSFET is just a switch (in this situation), yes. You need to make sure it can handle the peak current for your arrangement, and that the threshold voltage (VGS) is below about 4V - ideally below 2V (-4 and -2 for P FETs). P FETs switch the anodes, and N FETs switch the cathodes. Multiplexing is just rapid switching on and off of LEDs so fast you can't see it.
    – Majenko ♦
    Sep 17, 2018 at 9:40
  • thanks for reply. last thing could you provide p channel mosfet name (like IRFxxxxx) for multiplexing RGB leds. i dont have enough knowledge about electronic components.
    – begin123
    Sep 17, 2018 at 17:04

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