Do-Everything LED Indicator Light Runs From 4V To 60V

If you’re working with 3.3V or 5V circuits, it’s easy for you to throw on a power or status LED here or there. [Tom Gralewicz] has found himself in a pickle, though, often working on projects with voltages like 36V or 48V. Suddenly, it’s no longer practical to throw an LED and a resistor on a line to verify if it’s powered or not. Craving this simplicity, [Tom] invented the Cheap Universal LED Driver, or CULD, to do the job instead.

The CULD is designed as a simple LED indicator that will light up anywhere from 5V to 50V. It’s intended to be set-and-forget, requiring no fussing with different resistor values and no worries for the end user that excessive current draw will result.

The key part ended up being the LV2862XLVDDCR – a cheap switching regulator. It can output 1 mA to 600 mA to drive one or several LEDs, and it can do so anywhere from a 4V to 60V input. Assemble this on a coin-sized PCB with some LEDs, and you’ve got your nifty do-everything indicator light. With a bridge rectifier onboard, it’ll even work on AC circuits, too.

[Tom] has built a handful himself, but he open-sourced the design in the hopes it will go further. By his calculations, it would be possible to build these in quantities of 1000 for a BOM cost of less than $0.50 each, not counting assembly or the PCB itself. We’d love to see them become a standard part of hacker toolkits, too. If you’ve got a pick-and-place plant that’s looking for work this week, maybe get them on to something like this and see what you can do! If it turns out to be a goer, maybe drop us a note on the tipsline, yeah?

31 thoughts on “Do-Everything LED Indicator Light Runs From 4V To 60V

  1. How times have changed. Not long ago, you would do that with just 2 components, a JFET or a depletion-mode MOSFET and a resistor. Or if you were too lazy to calculate the resistor value, you would use a current regulating diode. No need to even think about EMI/RFI compliance.

  2. Even today, for a pilot light, I’d do with just 2 components: LED and resistor. If the 48V system had an existing step-down able to spare 2 or 3mA, then I’d use that. If not, then I’d want a good reason to not just accept 10mW or so dissipation in the resistor.

      1. hmm… a decent LED will light pretty bright on 1mA.

        A red LED, 1.6V, so for 48V that would require 46,4V to be dropped on the resistor.
        46,4V * 1mA = 46,4mW of power lost over the resistor (which needs to be 46,4V/1mA=46400Ohm, but lets use 47K for simplicity.

        Now what’s the problem? Just look for a decent LED, the time where we needed to force 20mA through an LED is way beyond us. This is 2023, LED’s are ridiculously efficient, unless you use the cheapest ones you can find (undocumented in an unsorted bag of 100 from an aliebay seller)? But what’s the gain if you need to add a “complex” circuit? You get what you pay for.

        However, if you want your indicator to be seen at full daylight, outside, in the bright sun, good luck anyway…

        1. The chance you get a very low current LED from China are much higher than finding one in local shops.
          The local shops often have old stock and China runs through them in the millions and restock with the latest constantly.

          But oh, sorry, it’s just about bashing China right? Excuse me, I keep forgetting.

  3. > it would be possible to build these in quantities of 1000 for a BOM cost of less than $0.50 each

    of you could just buy Chinese “LED Voltmeter Digital Voltage Tester DC 0-100V 0.36″ 4 Digit 3 Wire Panel Meter” Voltmeter for $1 with free shipping 3 wire setup, can be powered from same pin its measuring as long as its >3V, STM8 based and easily reprogrammed if you want something fancy.

  4. Fun to read the responses of people who haven’t actually read the blog, CL2? In the post.
    1ma LED? Not sunlight visible. 3 wire volt meter? The need a power supply under 30V.

    Its about about not wasting power in a battery operated environment. And as long as we’ve got the circuit, why not make it able to drive 1W LEDs, COBs, banks of LEDs, etc.

    One solution for most LED driving needs.

    Status lights on an electric golf cart? Why have a different solution for 24, 36, and 48V models? Same for fork lifts. Want LED headlights on those machines? How about interior lights, or ?
    Built a power wheels car and need to show status of BMS but not sure what voltage you’ll run in the final version?

    More complex than most solutions? Yes, less complex than stocking indicators for 10 different values of 1W resistors and giving them enough air flow not to cook.

    Its not the simplest solution, its one that minimizes the users time and effort.

  5. I’ve used Kingbright SMD LEDs on my last half-dozen projects, and every time I half the current because they’re way too bright to be effective indicators, and they’ve still ended up being way too bright.

    On my current project they’re running on 1mA and they’re literally daylight readable. I am going to run them on 0.5mA on my next project, but I expect the same thing to happen again. They’re basically homeopathic.

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