Small LED Current Limiters

Discussion in 'Tips and Tricks' started by AA4PB, Jul 21, 2021.

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  1. AA4PB

    AA4PB Ham Member QRZ Page

    While rigging up some backlight LEDs for meters, I ran across these small LED Current Limiters from that automatically limit the current through a string of LEDs. Even if the supply voltage changes, the current remains constant. They are available in 10mA and 20mA models. They are only $5.91 for ten units. Much nicer than using a resistor.
    NY4Q, WE4E and N0TZU like this.
  2. NC5P

    NC5P Ham Member QRZ Page

    ON Semiconductor makes those. They also have larger current models and you can parallel them to get even more current. I used to work for a lighting company that bought hundreds of thousands of them on reels.
    AB1YW and N0TZU like this.
  3. AA4PB

    AA4PB Ham Member QRZ Page

    ON Semiconductor probably makes the SMD devices, but provides them mounted on a tiny PC board with through hole solder points to attach your wires and clear heat shrink tubing to insulate the assembly.
  4. KS2G

    KS2G Premium Subscriber QRZ Page

    Good tip.
  5. W0RIO

    W0RIO Ham Member QRZ Page

    What part numbers are you using? A quick Google search showed the ON Semiconductor NSI45030, a 2 pin
    30mA current regulator and the NSI45015, a 15mA current regulator.

    I've built many versions of an LED current regulator that uses a common LM317L and a resistor to set the
    current value. It can regulate two white LEDs or three red LEDs using a 12VDC supply.

    I made a circuit board layout with Eagle CAD and had a few boards made by a Chinese PC fab
    for a small amount of money.

  6. NC5P

    NC5P Ham Member QRZ Page

    NSI, NSIC, NSVC series. They make 15, 20, 25, 30, and 50 mA versions. You can parallel them to get whatever current you want. Many of these parts are backordered now. The nice thing about these is they only have two terminals so are easy to use. I have also used a simple current limiter with NPN, MOSFET, and two resistors to accomplish the same thing. It costs less than the ON Semi part when you are building millions of LED boards and supply chain issues are almost eliminated. Transistors cost around one to two cents and resistors less than a cent. The ON IC's are quite a bit more than that. It does matter when you are running 500,000 or more boards. Eventually the company I worked for transitioned over to that solution to save money. I never heard any complaints from customers about the brightness being effected in any way.

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