8 Grove Bar Graph at same time

Community Project Proposal
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Hi everyone,

I am using the Grove Mega Shield : seeedstudio.com/wiki/index.php?t … ega_Shield with my Arduino Mega 2560

I want to use 8 Grove LED Bar Graph at the same time… seeedstudio.com/wiki/Grove_-_LED_Bar

Of course this doesn’t work because the card doesn’t provide enough power. Even with an external power supply of 12V.

What should I do ? Can I change the brightness of the LEDS ? Or I should use a ULN2803 ?

Thank you

1 Like
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Did you manage to solve this ? I’m on the exact same situation. I was planning to remove the vcc wire (red) from the connectors and plug to an external supply and then setting a common ground between the arduino usb gnd and the power supply gnd, I think that should do the trick.

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If you’re powering the Grove shield from a 12V external power supply, the onboard regulator of the Arduino or shield likely can’t supply enough current. Instead:

  • Use a dedicated 5V power supply (e.g., a 5V 5A switching power supply).
  • Cut the VCC trace going from the Arduino’s 5V to the shield (or modify wiring) so that you can supply 5V directly to the Grove modules.
  • Connect GND of the external power supply to Arduino GND to share a common ground.

You can inject 5V power using the Grove shield’s EXT_PWR screw terminal block (check Seeed’s documentation for this).

You can also use ULN2803 for Power Switching. How to make a water level meter with uln2803 - Share Project - PCBWay

The Grove LED Bar is based on the MY9221 or MY9231 LED driver IC, which controls current internally, so it’s not meant to be driven via ULN2803 directly unless you’re trying to switch power to the whole bar.

You can use a ULN2803 (or MOSFETs) to:

  • Switch the 5V power supply to each LED bar
  • Isolate high-current loads from the Arduino

However, this is usually overkill unless you’re dynamically switching bars on/off to conserve power.