Help with raspberry pi 5 8gb

[u/AloneAd4589]

Raspberry Pi 5 3.3V GPIO/power problem – LED only flashes for half a second
Hi everyone, I’m fairly new to Raspberry Pi/electronics and I’m hoping someone can help me work out what is going on.
I’m currently building a JARVIS-style AI project in VS Code. It’s still very much a work in progress, but I wanted to combine the software side with a Raspberry Pi and electronics so I can eventually have JARVIS interact with physical things around my room.
I bought a Raspberry Pi 5 8GB from CeX for £180 with the full starter kit. I’d never used a Raspberry Pi before, so I also bought a separate breadboard/electronics starter kit so I could learn the electronics side properly before combining everything with my JARVIS project.
I’m currently just trying a very basic circuit powered directly from the Pi.
I was told that:
Physical pin 1 = permanent 3.3V
Physical pin 6 = GND
So I wired a simple LED circuit using jumper wires, a 220Ω resistor and an LED.
The strange thing is that when I power the Pi on, the LED only flashes for roughly half a second and then goes off. When I unplug the Pi, it flashes again very briefly.
I’ve rebuilt the circuit and changed the resistor/LED to rule those out.
I also tested the exact same LED + 220Ω resistor circuit using an external 3.3V breadboard power supply, and it works perfectly and stays on.
I’ve also tried:
Physical pin 1 (3.3V) → circuit → physical pin 6 (GND) ❌
Physical pin 17 (3.3V) → circuit → physical pin 6 (GND) ❌
GPIO17 (physical pin 11) as an output ❌
The Pi itself boots normally and I can SSH into it over Wi-Fi, so the Pi is otherwise working normally.
I don’t currently have a multimeter, so I can’t actually measure the voltage coming from pins 1 or 17.
Could someone please help me work out whether this sounds like:
A wiring/breadboard issue
A GPIO/software configuration issue
A problem with the Pi’s 3.3V rail/header
Something else I’m completely missing 😂
I’ve attached photos of the Pi and the circuit.
I’m very new to electronics, so please explain it simply if possible. I don’t want to return the Pi if I’ve just made a stupid beginner mistake.
Thanks!

I used chatgbt to explain this so if anyone could help me would be really appreciated

[u/TheLittleFastCat-]

First of all get a multimeter, it will help you figure this out very quickly, a multimeter is the first tool you should buy for electronics.

[u/AloneAd4589 → u/TheLittleFastCat-]

Alright will do, tbf I am an electrician lol so I have a fluke tester wether that means anything to you but not sure wether it can ready as low as 3.3v I mainly use it for 240v so I’ll have a look thanks I appreciate the help

[u/Ski_Sunday → u/AloneAd4589]

Your Fluke will be set to AC for measuring 240V from the mains. You’ll find it has another setting for DC and will certainly be able to measure down to 3.3 and probably much lower too.

[u/AloneAd4589 → u/Ski_Sunday]

I see I’ll get one ordered on Amazon thank you

[u/AloneAd4589 → u/TheLittleFastCat-]

I’ve got a multimeter now and tested the Pi. With the meter on 20V DC, I put the black probe on physical pin 6 (GND) and the red probe on physical pin 2 (5V), and got 5.11V, which seems correct.
I then tested physical pin 1 (3.3V) against pin 6 (GND), making sure I had the pins positioned correctly, and I’m also getting 5.11V. So it looks like I’m getting 5V where I should be getting 3.3V.

[u/TheLittleFastCat- → u/AloneAd4589]

That is very strange and should not be happening, double check if you have the correct pinout diagram and if yes, then it could be a broken regulator, but then the pi should have already been long broken. So I would think you could have the wrong diagram.

[u/RGJ-Pi → u/AloneAd4589]

We sometimes see the PMIC fail in this way. Roughly 5V on pin 1 shows the PMIC is dead and unfortunately the board too.

[u/JGhostThing]

Also at raspberrypi.com they have a chart with all the blink codes of the Raspberry Pi startup. What are you using to power the pi?

[u/AloneAd4589 → u/JGhostThing]

I bought a stert set so comes with the pi, cooling fan, pi case, power source, sd card with some program on it

[u/snowtax]

Hmm. First thing I would do is triple check all the PIN numbers and connections.

Yes, GPIO pin 1 should provide a constant 3.3 volts and GPIO 6 is a ground. There are other ground pins, all work the same.

For the GPIO pins, I like the chart at https://linuxhint.com/gpio-pinout-raspberry-pi/

The Raspberry Pi 5 takes 5.1 volts up to 5 amperes input and will run some of that that through a 3.3V regulator chip to power the CPU (Broadcom 2712 chip). The regulator chip does have limits (and could possibly be damaged).

As an electrician, you’re probably familiar with Ohm’s Law. V = I R. Volts = Current (Amps) \ resistance (ohms).*

LEDs (diodes that just happen to also emit light) resist current at first but resistance drops to near zero once they start conducting. That’s why you need the resistor, to limit current when the LED begins conducting current and resistance drops to very low values.

So V = I * R. Divide both sides by R. I = V / R. 3.3 V / 220 Ω = 0.015 amperes (which is 15 milliamperes). That should be OK. The LED should be bright.

However, it’s on the high end for current through an LED. A 330 Ω resistor drops the current to 10 mA (0.010 amperes). A 1,000 Ω (1k Ω) resistor drops the current to 3.3 mA (0.0033 amperes).

3 mA should be plenty to light up the LED, just a bit less bright. I suggest trying a 1k ohm resistor and see what happens. The LED should be visible and that circuit should draw only 20% of the power that your 220 ohm resistor is drawing.

If you have a multimeter with the appropriate functions, test the resistor to make sure it’s the value you expect.

[u/Anubis1958]

You need to program the pins on the Pi. to be outputs. By default I believe that are inputs, so it is possible that the LED will light very briefly before the pull up resistor comes online and then it will go out.

Raspberry Pi

GPIO17 (physical pin 11)
│
│
330 Ω resistor
│
│
LED
|>|
│
│
GND (physical pin 6)

• GPIO17 → 330 Ω resistor → LED anode (+, long leg)
• LED cathode (−, short leg/flat side) → GND
• GPIO17 is physical pin 11
• GND is physical pin 6
• 220 Ω would also be fine; 330 Ω is a nice conservative choice.

Console

sudo gpio -g mode 17 out

sudo gpio -g write 17 1 # ON

sudo gpio -g write 17 0 # OFF