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Thread: Teensy Power from source other than USB

  1. #1
    Junior Member
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    Teensy Power from source other than USB

    I am using a Teensy 3.2 and FastLED to control a strip of 840 12 Volt WS2812 LED's.

    I'll be powering the Teensy from the 12 volts powering the LED's through a Buck Converter that has the output voltage dialed down to 5.0 volts.

    Here is my problem; when I have the Teensy on the workbench powered through a USB cable connected to my PC; everything runs perfect. When I remove the USB and try to power the Teensy from the Buck Converter, the Teensy does not work. I've tested the Pins on the Teensy and I'm getting 5.0 volts to the GND and Vin pins and the voltage is the correct polarity.

    I am stumped.

    Any similar experience with this problem out there?

    Appreciate the help,

    Bob

  2. #2
    Senior Member+ defragster's Avatar
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    Have you programmed a simple blink running from the Buck Converter? Enough to show it works at all from that power source? Can you measure 3.3V from that pin then?

  3. #3
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    Good idea. Ran a blink and I get 3.3 volts at pin 13 and the board LED blinking with both the USB power and Buck Converter. Chip is at least alive.

  4. #4
    Senior Member+ defragster's Avatar
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    Put a couple second delay in setup() with a blink to show it is alive.

    while(millis()<5000) {
    digitalWriteFast(LED_BUILTIN, !digitalReadFast(LED_BUILTIN) );
    delay( 250 );
    }
    May be 'warm start' when on USB and a race otherwise - not sure what other things are in the system. Put that blink in your loop() maybe too.

  5. #5
    Senior Member+ MichaelMeissner's Avatar
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    Cool

    Also make sure you don't have loops like the following in startup, which will wait forever for the USB serial connection to start up.

    Code:
      while (!Serial)
        ;
    If you do want to do Serial output when the USB is attached, you can put a timeout such as this which waits for a maximum of 3 seconds for the USB serial connection, and if it doesn't get connected, it will go on. The Teensy Serial library is robust enough that it will ignore Serial.print and Serial.println if there is no USB connection:

    Code:
      while (!Serial && (millis () <= 3000))
        ;

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