I am following the adafruit for driving LEDs from the pi.

They suggest wiring it like this (this works great for me btw, no flickering):


This is how mine is wired:

my wiring

I'm sure some eyesores jump out at you:

  • wiring color
  • melted squares from when my ground and power were touching D:
  • hot glue around the peripheral wires
  • crossing wires at the power supply adapter

I drew a sharpie line on the wires that are ground. When I wired it according to the guide, that is, with a breadboard that has vertical running lines for power and ground, it works great!

But moving it over to this mini breadboard it starts flickering. I tried powering the led wires (circled in blue) with a wire that goes straight to the power supply adapter output (yellow wire), and it was a bit better, but not much.

So does the voltage really degrade that much with traveling across the board to my led strip connectors? Is the breadboard crap? Does having dedicated lines for power/ground make that big of a difference? Do I need a bigger power supply?

update New wiring New bread board helped a lot with wiring the power in parallel. I grounded the unused inputs to the level shifter. I added a 1000uf 16v capacitor although a smaller one would have been fine. Also added a resistor as recommended by Neopixel guide. I bought a multimeter and can see that voltage drop is much lower and there is almost no flicker.

The little led just shows when my external supply is plugged in.

  • \$\begingroup\$ Welcome to EE.SE. Things seem ok, but you may be missing a crucial bypass capacitor across the supply leads. Any 470uF 16V/25V/35V aluminum radial capacitor with as short of leads as possible. They will take the flicker out of the power feeds. \$\endgroup\$ – user105652 Feb 14 '19 at 3:10
  • \$\begingroup\$ At the very minimum you cannot leave the inputs of your 74AHC125 floating, tie them to ground. The line driver may be oscillating. Secondly follow as @Sparky256 suggests and add a bypass capacitor. \$\endgroup\$ – sstobbe Feb 14 '19 at 3:25
  • \$\begingroup\$ You need a DMM to see the resistance by measuring the voltage drop on each joint and wire length. 10mOhm is ok at 1A but not >100 mOhm \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 14 '19 at 4:30
  • \$\begingroup\$ Thanks for taking a look. I didn't know what a bypass capacitor was. I read this: medium.com/supplyframe-hardware/… \$\endgroup\$ – Matt Wilde Feb 14 '19 at 9:36
  • \$\begingroup\$ If I understand correctly, I put a capacitor between power and ground right where my power adapter comes in to the board. And also put one on the data out pin of the chip, right? Would they both be 470uF? And sstobbe do all unused pins need to be grounded? @SunnyskyguyEE75 I don't know where those ohm numbers are coming from or how I should apply what you are saying. \$\endgroup\$ – Matt Wilde Feb 14 '19 at 9:45

These breadboard contacts are not intended to draw more than 1/4A so improve the connections with many more in parallel for V+, 0V.

  • \$\begingroup\$ 'improve the connections'. All of the connections? which connections? 'many more in parallel' perhaps link to an image showing an example of that please. \$\endgroup\$ – Matt Wilde Feb 14 '19 at 13:37
  • \$\begingroup\$ How about 6 or 8 jumpers in parallel for V+ and V- and to LED from IC and NOT 3. Proto boards must NOT be used for high current outputs. and if you don’t learn OHm’s Law , how old are you? You can calculate 1.4A / 1/4. = 6.4 so I suggested 6 to 8 parallel wires to share 1.4A \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 14 '19 at 14:28
  • \$\begingroup\$ Adafruit examples are sometimes done by rookies. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Feb 14 '19 at 14:33
  • \$\begingroup\$ To be honest age isn't relevant here. If you'd like to ask me more about my background and why I'm not experienced, I'd be happy to oblige. \$\endgroup\$ – Matt Wilde Feb 14 '19 at 15:11
  • \$\begingroup\$ I've done some more digging into capacitors, farad measurements, other examples of led wiring with the pi, neoPixel best practices, and using a level shifter \$\endgroup\$ – Matt Wilde Feb 15 '19 at 22:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.