Raspberry Pi not recognised when connecting power cable to wall sock but is when connected to laptop

Question

Pi setup is as follows:

• version 4B
• 64 bit OS
• ethernet cable from router to Pi
• power cable from Pi to laptop USB port
• SD card 16 GB
• Router recognizes, lists Pi in devices, can SSH to it

If I move the connection of power cable USB end from laptop to iPhone plug in wall socket, I see power lights, ethernet lights as before on the Pi, but the device isn't listed on the router. Why is this? How do I resolve this?

I have enabled SSH, userconf has username:hash-password, wpa_supplicant.conf as follows:

country=GB
update_config=1
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev

network={
    scan_ssid=1
    ssid="xxxSSIDxxx"
    psk="xxxPasswordxxx"
    key_mgmt=WPA-PSK 
}

Answer 1

You are suffering from a classic problem of not enough power. Assuming you have 3 cores it needs about 5 watts of power. The Raspberry Pi 4 requires a power adapter that outputs at 3 Amps at 5 Volts. The iPhone will give you 5V at how many watts? There is a reason they recommend minimum capacity form the power supplies, you are experiencing it. If you connect peripherals add the additional power requirement(s) to the power supply requirements. I will say A proper power supply will solve your problem.

USB 2 ports are designed to supply 5V of electricity with a maximum current of 0.5A. This wattage is standard standard across the majority of computers and means the overall power output will be 2.5 Watts at best.

USB 3 ports are designed to provide up to 900mA or 0.9A, which translates into 4.5 watts.