Reader, you may recall I had decided to make a low power media streaming server using a Raspberry Pi 5 (RPi5) with attached usb hard drives.
The RPi5 works when connected to a standard usb power source. However there is a low power warning if the RPi5 detects the power source is insufficient to power attached external devices (eg, usb hard drives).
The Raspberry Pi company sell a high power device for the RPi5. It's rated at 27 Watts. All RPi's operate on 5 Volts. The advice from the Raspberry Pi company is a RPi5 requires a minimum of 5 Amps. Their power source is rated at 5.4 Amps.
Purchasing an official RPi5 power supply has two disadvantages. 1. Delivery would take two weeks. 2. The postage added 33% to the total cost.
Looking for an alternative I found a local computer store selling a usb power source rated at 30 Watts. Not only was it cheaper, but more powerful. I purchased one and the RPi5 worked.
However this morning I found the RPi5 had stopped working ?????? I couldn't get it to start with the external usb hard drives connected. When these were disconnected the RPi5 would start but displayed the following screen message.
The problem couldn't be the power supply as it's rated at 30 Watt (6 Amps). Perhaps it was the cable between the power supply and the RPi5.
I connected my USB Tester between the power supply and the RPi5
There was 5V and only 0.77A.
After a period of various trials I reverted back to the original power supply
The RPi5 worked. Albeit the external usb hard drives were not attached and I wasn't getting the low power warning
Next I plugged in the four usb hard drives and they were recognised.
But the system has lag and sometimes freezes. Obviously the original power supply doesn't have enough power. But it's doing better than the 30 Watt device.
The 30W power supply is marked as 30W. It's grey text on a grey case so you will have to take my word for it.
Then I realised there was some tiny grey on grey text on the side of the case. I've done a Kate and enhanced it
The problem has been revealed. The power supply is rated at 30W when drawing 15V @ 2A. The RPi5 needs 5V and the device can only supply a maximum of 3A (5Vx3A=15W) My 30W supply can only produce 15W at 5V. This is insufficient to adequately power the RPi5 when the usb hard drives are attached.
Bugger!
2 comments :
Tom. Can you not use a separately powered USB port to run the disk drives? I have a 4 port extender that copes with the drives power requirements leaving the Pi to it's own PSU.
Graham,
Both dual slot usb external ports are separately powered. However the Pi OS still requires a higher power supply (5A). It will run with a standard 2A source but freezes when any external devices are attached. Well that's not strictly true as I have a wireless keyboard dongle in one of the onboard usb ports and the bottom HAT for the NVMe drive is also attached.
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