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I have about 30 small white LEDs tightly packed in a column to together form a value indicator (imagine "virtual mercury thermometer"). I would like to control them as a group with a microcontroller, but they have to be driven with high-quality PWM and individually addressable.

My first idea was to use off-the-shelf addressable LEDs, however I didn't find any that were suitably small.

My second idea was to use the WS2811 (or something similar that doesn't need 12V) and connect each of the channels to one LED, but it seems kinda dumb to have 10 of these chips.

Is there some kind of low-voltage LED driver IC that satisfies my requirements above?
If not, what are your other ideas?

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    \$\begingroup\$ The WS2811 doesn't "need" 12V, that's its absolute maximum for the LED outputs. \$\endgroup\$
    – Finbarr
    Commented May 9, 2022 at 14:53
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    \$\begingroup\$ Ugh why are people voting to close this as a recommendation question. Asking for alternative engineering methods is not a recommendation question. \$\endgroup\$
    – Passerby
    Commented May 9, 2022 at 16:50
  • \$\begingroup\$ search "LED bar graph IC"? \$\endgroup\$
    – Criticizing Israel not allowed
    Commented May 9, 2022 at 17:47
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    \$\begingroup\$ this may help ... duckduckgo.com/?q=tm1812&ia=web \$\endgroup\$
    – jsotola
    Commented May 10, 2022 at 0:58
  • \$\begingroup\$ It would be good to know what are your actual dimensional limits (i.e. how small your control circuit has to be) and the specs of those LEDs. Some high efficiency LEDs can be driven with a couple milliamps and still be quite bright. Knowing this information would open up more design options. \$\endgroup\$
    – LorenzoDonati4Ukraine-OnStrike
    Commented May 10, 2022 at 11:06

3 Answers 3

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You want led matrix driver or multichannel led pwm driver ics. Most can handle the pwm and dot control themselves as well. You may need a microcontroller locally depending on your setup.

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    \$\begingroup\$ @KryštofVosyka, Hint: Just because some IC expects LEDs to be electrically connected in an MxN matrix, that doesn't mean that you can't physically arrange them in some different way (e.g., by putting all of the "rows" or "columns" end-to-end in a single straight line.) \$\endgroup\$
    – Solomon Slow
    Commented May 9, 2022 at 16:10
  • \$\begingroup\$ In the end, two of the TLC5946 seems like the easiest solution, they can be bought dirt cheap on Aliexpress. \$\endgroup\$
    – Kryštof Vosyka
    Commented May 10, 2022 at 17:53
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One of many solutions: get a microcontroller with 44 pins – cheapest you can find, and drive the LEDs using an NPN transistor as a buffer. Some microcontrollers may be able to drive all those LEDs without buffers. The microcontroller should cost about $1 for this application. It really can be as basic as you wish, and will still be able to do the job. You can command it via SPI, I2C or UART.

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  • \$\begingroup\$ Rolling your own 30 led pwm addressable driver seems... onerous. \$\endgroup\$
    – Passerby
    Commented May 9, 2022 at 16:58
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    \$\begingroup\$ @Passerby It’s a page of C, or maybe two pages of assembly. Sure, it needs to be debugged and tested, but it’s dirt cheap if you need it in volume and it looks like the MCU may have better availability than the matrix drivers. \$\endgroup\$
    – Kuba hasn't forgotten Monica
    Commented May 9, 2022 at 18:24
  • \$\begingroup\$ Since I need separate PWM per LED (which most matrix drivers don't have) and you can get a MCU for 60 cents a piece, I'm starting to like this idea. \$\endgroup\$
    – Kryštof Vosyka
    Commented May 9, 2022 at 20:57
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    \$\begingroup\$ @KryštofVosyka many multichannel led drivers have independent pwm grayscale pwm control on all channels, but sure won't meet a 60 cent price. Your paying for the software development, guaranteed behavior and constant current control plus other features. \$\endgroup\$
    – Passerby
    Commented May 9, 2022 at 22:46
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Another option: there are various LED driver ICs that are basically a shift register with output stages to drive LEDs, e.g. TLC6C5912, see the data sheet

They can be driven from an SPI interface, and chained to drive larger numbers of LEDs.

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