Igor Kromin |   Consultant. Coder. Blogger. Tinkerer. Gamer.

Some time during the week I noticed my digital photo frame stopped working. It uses a Raspberry Pi model A to run the jPhotoFrame software and sometimes the screen fails to turn back on after going to sleep overnight. This time the problem was different however. I noticed that the red power light on the Raspberry Pi was constantly flashing.

This is what I was seeing...



According to the R-Pi Troubleshooting page...
A blinking red power LED indicates problems with the power supply. On model A and B, it is hard-wired to the 3.3V power supply rail. If it is blinking, as one user has reported[1] it means the 5V power supply is dropping out. Use a different power supply.


Well the fix was easy then. My power supply was connected to a USB hub which then powered the RPi and the USB monitor, WiFi dongle, etc. Luckily I had an identical power supply as a spare. Plugging the other power supply let the photo frame start and boot normally. So problem fixed, but I wanted to know why it actually happened in the first place.



I checked the voltage output on both power supplies and it was pretty much the same and stable, so that wasn't it.

IMG_0830.jpg IMG_0831.jpg


I didn't want to do any rewiring so didn't measure the current output, but this is what I suspected was going wrong. The power supply is a model WT0502000-MID which is rated at 5V 2A output.

I did a rough calculation of power requirements: 1A for the USB monitor (5W @ 5V according to specs), 150-300mA for the RPi (depending on load), 100mA for the WiFi dongle, 50mA for the USB storage. That's around 1.9A and is quite generous with actual values probably quite a lot less. Still this was close to the maximum output for the power supply. Still no problems, until I realised that I also had my RGB LED clock connected to the same USB hub as well.

The clock LEDs alone add around 6x 20mA of current draw, for a total of around 120mA, and this pushes the total current draw over the 2A maximum. Running it all like this for several months is what I believe caused the original power supply to stop working at it's peak output.

Lesson learned, lets see if the reduced current draw without the clock plugged in helps.

-i

Please leave your comments or feedback below!
comments powered by Disqus
Other posts you may like...
Hi! You can search my blog here ⤵
Or browse the recent top tags...

Recent Blog Posts

Tiny Arcade revision 6 kit assembly and decal application

Jersey JAX-RS filters and interceptors execution order for a simple GET request

How to stop macOS adding shadows to window screenshots

How to run Atari Lynx games on the SNES Classic Mini

Maven dependency scopes with relation to WAR file packaging and the WEB-INF/lib directory

Hacking the Sonoff B1 WiFi LED bulb to run custom firmware

What does an idle WebLogic server run on the hour to cause a CPU spike

How to open the Sonoff B1 wifi LED bulb to access its internal circuitry

Australian release SNES mini classic unboxing and a quick play through

Troubleshooting high CPU usage for JVM threads

Recent Galleries

Atari Lynx repair - Part 5 - McWill LED screen mod installation

Atari Lynx repair - Part 4 - screen cover replacement

Atari Lynx repair - Part 2 - re-capping the motherboard

Atari Lynx repair - Part 3 - broken speaker replacement

Atari Lynx repair - Part 1 - introduction and case disassembly

Building a custom Atari Lynx game box storage shelf unit in a day

Protecting old Atari Lynx game boxes with snug fit plastic sleeves

Monument Valley 2 is released and does not disappoint

Space Food - Chocolate Ice Cream with Chocolate Chips

Legeod Star Wars AT-DP kit

Blogs and Friends

Matt Moores Blog
Georgi's FlatPress Guide
Perplexing Permutations
The Security Sleuth
Ilia Rogatchevski
Travelling Fairy

Blog Activity

Blog Activity