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?
LEDs are current-driven elements so they don’t really care about voltage. I guess you could regulate them with a basic 2N2222 circuit.
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.
Or a light bulb with a filament and a length of wire.
“current regulating diode”? Can’t say I’ve every heard of that! Any details, please?
https://eu.mouser.com/c/semiconductors/discrete-semiconductors/diodes-rectifiers/current-regulator-diodes
I remember thinking “Wait, what?” when I first heard about those.
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.
It will be more like 1W of dissipation instead of 10mW for a led on 48W
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…
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.
+1
No problems with cheap Ali LEDs. Please stop this China BS already.
> 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 https://hackaday.io/project/16097-eforth-for-cheap-stm8s-gadgets/log/52998-yet-another-voltmeter. 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.
No.
Yes.
Maybe
Sometimes
Come to think of it, don’t they sell LED with circuits inside of them that can handle a very high range of voltages? Might be a fraction of the cost.
Big Clive did a video on those 7 years ago, but all were constant voltage
https://www.youtube.com/watch?v=fUTiYs3i4Cs
No need to mess around with resistor values – uses 10 components instead :/
Over engineering at its finest
I generally use a CL2 led driver.
I always use this circuit: https://www.electroschematics.com/led-constant-current/
Two npn transistors and two resistors, simple and easy. It is also possible to control it with a uC by connecting the 2k2 resistor to a GPIO.
That is a neat circuit. There are so many ways to approach this problem and this sits nicely between crude and elaborate.
I need 0-25V
from solar panel, battery, 3v, 3.7V usb, car baterry etc.
You’re gonna have to bend on that 0 requirement.
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? https://powerracingseries.org/
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.
Absolutely. It’s a swiss army knife indicator that minimises the engineer’s time spent having to solve a trivial issue.
Good point, the had summary does not really convey that it’s for more uses than a indicator.
And I did not read the full blog :D
Nice reinventing a cheap buck converter. I’ll just buy one from china for less than a buck.
Totally missed opportunity on the acronym though
CHeap Universal Driver – CHUD
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.