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first post here but I've been doing some research and cant find a definitive answer.

Goal: Use some type of voltage-controlled switches in parallel (similar to schmitt trigger) that will accept PWM DC power from an Arduino Uno that will all actuate at different times (voltages).

Example: Source voltage is 6v, I want an array of 5 LEDs that can be turned on/off individually, each one triggering at a different input (1 Vdd each) from a single Arduino PWM pin.

I would like to use simple components that I already have (good selection of transistors, diodes, resistors, capacitors etc.), and don't mind building a circuit that's already on an IC if it means I don't need to go get parts.

I've looked into Schmitt Triggers and can't find a version that will run off of PWM DC power, AC only (kinda the same thing? couldn't get it to work). I'd like to avoid the 74HC595 because it requires 3 inputs not one. Physical size isn't a problem, only specialized parts. Tried using simple transistors as switches but there's a lead in/out dimming effect, I want as close to all the way off and all the way on as possible. I also looked into a 555 timer option where there's a voltage divider network leading to each timer, and pins 2/6 on the timer were inputs from the Arduino, but couldn't quite get that to work also (with the whole 1/3 and 2/3 being on and off instead of being relatively close).

If I'm missing any crucial info please let me know! I'll be pretty happy if there's a simple fix that I'm overlooking, thanks!

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  • \$\begingroup\$ There's no such thing as "PWM DC power" - that's an AC signal like any other. \$\endgroup\$ – Nick Johnson Jun 18 '15 at 9:41
  • \$\begingroup\$ I know PWM alternates between 0 vdc and 5 vdc (in this case), but I thought to be AC power (by definition) it needs to alternate into a negative voltage as well (-5 to 5 for example) \$\endgroup\$ – Taylor Roysdon Jun 19 '15 at 3:11
  • \$\begingroup\$ No, that's just a matter of DC bias. Your PWM signal is a 5Vp-p AC signal, with a 2.5V DC bias. \$\endgroup\$ – Nick Johnson Jun 19 '15 at 8:43
  • \$\begingroup\$ Use addressable led's, google it. \$\endgroup\$ – Codebeat Nov 23 '16 at 0:09
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The LM3914 is a bar graph driver that handles up to 10 LEDs with a single chip (and is cascadeable to... I don't know how many dozens). Simply put a LPF on the PWM output and pass it to an appropriately configured LM3914 and you're done.

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  • \$\begingroup\$ Thanks! I ordered a few of those and I'll update here how it all works out :) \$\endgroup\$ – Taylor Roysdon Jun 19 '15 at 3:08
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Serial in Parallel out LED drivers exist for this. Feed the logic IC a serial input which turns on/off specific outputs. You can even get them with constant current sources integrated. For example: TI TLC5925, 8 or 16 outputs. Dimmable if desired.

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