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Thread: Can I power a second Teensy LC from another Teensy LC that powers 30 LEDs?

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    Can I power a second Teensy LC from another Teensy LC that powers 30 LEDs?

    This is probably a real noob question. I'm a long time programmer and pretty confident in the logic department but I've always had issues with understanding the electronics fully. I'm getting better at it but still learning. My simple and noobish question is: can I power a second Teensy LC from another Teensy LC that in turn is powered by USB? If so, please show me. I'm guessing utilizing pin 17 in some way. Also of interest might be that is the second Teensy is powering a Neopixel with 30 LEDs (which probably would work fine using 3.3V anyway).

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    Senior Member+ Theremingenieur's Avatar
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    30 simple LEDs 20mA = 600mA. 30 RGB LEDS 60mA = 1800mA. Both variants exceed the USB specification where one port can deliver a maximum of 500mA. Thus, you'll have to invest into an extra power supply for the LEDs.

    On the other side, powering two Teensys from one USB can simply be done by connecting the 5V and the GND pins.

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    Ok. But I'm already able to do the animations using just one USB cable and 60 LEDs. Granted not all LEDs are on simultaneously and I'm testing on a Arduino UNO. I'll have to check and do some measurements later.

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    Senior Member+ Theremingenieur's Avatar
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    Quote Originally Posted by sebrk View Post
    Granted not all LEDs are on simultaneously...
    Professional circuit design requires taking all "worst case" scenarios into account. And yes, there are "USB chargers" like the one for the iPads which can deliver up to 2.4A. But you can't know in advance how your clients or end users for which you develop a device will hook up things. Imagine that someone connects your circuit to a laptop whose main board will go up in smoke because more than 500mA were drawn from the USB port. Such things could ruin your business (and your reputation as an engineer).

  5. #5
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    This project will not leave my home fortunately even though I get what you are saying and agree. I will have to think twice here and maybe add external power. Could you provide me with links to a product that will fit my needs? Regardless I need the USB for data. It is connected to a desktop computer.

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