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Powering a Trinket M0 using external DC power supply
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Powering a Trinket M0 using external DC power supply

by RockB on Wed May 20, 2020 1:15 am

Hello,

I want to use a 12 LED RGB Neopixel ring (https://www.adafruit.com/product/1643) with trinket M0. Can trinket M0 be powered from a 5v DC power supply directly soldered to board using JST connector? Are there any special requirements on the power supply?

Also, in my project, all LEDs will be ON and color changes depending on certain digital inputs from external devices. How many such 12 LED rings can a single Trinket M0 board drive?

RockB
 
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Re: Powering a Trinket M0 using external DC power supply

by adafruit_support_bill on Wed May 20, 2020 5:23 am

See the pinout page here: https://learn.adafruit.com/adafruit-tri ... r-pins-3-3
You can power the board with 3v-6v via the GND and BAT pins.

RGB Neopixels require 3 bytes of RAM per pixel. (4 bytes for RGBW). The M0 has 32KB of RAM, so even allowing for stack and heap space, you have enough RAM for hundreds of rings.

Note that the logic level output of the board is 3.3v. Neopixels expect a control signal level of VCC * 0.7. If you are powering the pixels with 5v, that means you need a control signal of at least 3.5v for reliable operation. 3.3v sometimes works, but not always. You may need to add a level-shifter between the M0 and the first ring.

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Re: Powering a Trinket M0 using external DC power supply

by RockB on Wed May 20, 2020 3:09 pm

Thank you for the clarification. In the pinout for Trinket M0, I dont see any 5V output pin. The external 5V power supply powers both trinket and LED ring?

Also, for level shifting from 3V to 5V to drive the data signal for LED ring from trinket, can I use something like 74AHCT125 - Quad Level-Shifter (3V to 5V)? or do you recommend any other chip?

Could you provide me with a wiring example please?

Thanks!

RockB
 
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Joined: Wed May 20, 2020 1:01 am

Re: Powering a Trinket M0 using external DC power supply

by adafruit_support_bill on Wed May 20, 2020 3:39 pm

You should run power and ground to the rings directly- not through the processor board. You just need a GND and signal connection from the M0 to the first ring.

The 74AHCT125 is the recommended level shifter chip for use with neopixels.

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