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I am driving a common anode RGB LED using a 15mA constant current LED driver. What really confuses me, is that only the blue light works when plugged in. The red and green ones seem to be dead. Whenever the lead for Red or Green is plugged in, the voltage across either would drop from ~5V to ~0V. I haven't written any code yet, and need help in debugging the LED behavior.

Any input would be appreciated!

The red and green lights are still functional, as I can light them up by tuning a dc power supply. However, they wouldn't light up when connected to the constant current driver.

enter image description here

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    \$\begingroup\$ You'd need to supply a schematic showing how you wired it up. We can't guess. There's a schematic button on the editor toolbar. \$\endgroup\$
    – Transistor
    Commented Sep 29, 2020 at 19:03
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    \$\begingroup\$ That's a wiring diagram rather than a schematic and it doesn't show us the schema of your design. Those Fritzing diagrams are often called "cartoons" around here. It doesn't show us the function of the LED pins, the function of the pins on the blue board or the green board. To make sense of it we have to research three documents to understand the pinout. Fritzing may be able to export a proper schematic for you to upload. \$\endgroup\$
    – Transistor
    Commented Sep 29, 2020 at 19:36
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    \$\begingroup\$ I think as you draw the proper schematic it may reveal some errors in your thinking or your wiring. It should make it much clearer to you how the circuit is supposed to work. \$\endgroup\$
    – Transistor
    Commented Sep 29, 2020 at 19:48
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    \$\begingroup\$ That Fritzing "schematic" is only a slight improvement over the previous picture. It appears you have the cathode of the blue LED connected to +5V, and the comon anode of the LEDs and the red and green cathodes all connected to PWM pins - something is definitely wrong with the LED connections. \$\endgroup\$
    – Peter Bennett
    Commented Sep 29, 2020 at 20:07
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    \$\begingroup\$ The schematic is unreadable in its current form, please fix it \$\endgroup\$
    – Voltage Spike ♦
    Commented Sep 29, 2020 at 21:08

1 Answer 1

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Let's tidy up.

enter image description here

  1. Rotate 90° anti-clockwise.
  2. Rotate 90° anti-clockwise.
  3. Show your power supply ground connection. You can use GND symbols for everything connected to GND and eliminate some wiring to tidy up your schematic.
  4. Show your power supply + connection.
  5. Untangle the wires here. Can you see anything odd with the wiring of the three LEDs? (I can.)
  6. Sort out this neatly.

Try and make your schematics read neatly from left to right. Positive voltages go to the top and negative or ground to the bottom of the drawing. That's why, when you rotate the board schematics so that the text is the right way up you'll find the GNDs at the bottom and V+ at the top. The LEDs are the right way up.

Tidy up the wiring and add the new diagram to your post to show your progress.

When you do this the reason for your problem should become apparent.

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