Pi Zero W doesn't boot when powered via GPIO

Hi girls and boys
I am trying to power a Pi Zero W with an " Adjustable Switching Power Supply Module IN 4V-35V OUT 1.5V-30V LM2596S", on pins 4(+) and 6(-). Unfortunately Pi is not cooperating, and despite the LED blinking like it’s actually booting up, I get nothing on HDMI and Pi does not request an IP address. I can confirm Pi is very alive because it behaves when powered through the USB port. I though maybe there isn’t enough amps (or mA for that matter) coming out of the PS, but measuring the consumption, it never goes above 200 mA. I’m sure I am missing something… But can’t figure it out :frowning:

Pin 4(+) and 6(-) connect straight to the USB power connector according to the schematic. I’ve powered these boards like that before. I’d check that the supply doesn’t dip below 5V. I’ve had short spikes at startup on similar boards that I could only pick up with an oscilloscope. Sometimes just putting a large cap at the board helps especially if you have long supply leads.

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Right on target. Added a 470uf capacitor between 2(+) and 9(-) and works like a charm. :slight_smile: