General Pi project tips
In this Tech Tip, I'll try to give a few bits of advice about issues we often see when assisting our customers. I hope these tips will help you get a good start in your Pi projects!
Powering your Pi
How to power
The Raspberry Pi can be powered from the USB-C/micro-USB ports or a PoE(+) hat. However, for some projects, you may find powering it from the GPIO header is easier. As long as the voltage on the GPIO header +5V/Gnd pins stays in the 5.0-5.1V for currents of 0-3A, it should work! Just make sure the power source meets the technical requirements (see here: https://www.raspberrypi.org/documentation/computers/raspberry-pi.html#power-supply). See the official schematics for additional details: https://www.raspberrypi.org/documentation/computers/raspberry-pi.html#schematics-and-mechanical-drawings
Power quality
The Pi needs stable, computer-grade power which is 5.0V +/- 5%, with low ripple. This is the design goal of the power supplies we offer for use with Pis, they are stable in voltage for the current range they are rated for. If you want to use other power sources, you may need extra filtering to meet the quality requirements of the Pi. Keep the Pi voltage in the range 5.0V to 5.25V at all times! If you exceed this, you may damage the Pi and the connected devices!
Be aware that all power supplies are not created equal! For example, some produce an equipment-destroying spike on power-ups. Another frequent example is the phone charger: they are of varying qualities and are often of a quality barely enough to charge phones! If you plan on using power sources not designed for Pis or of unknown cleanliness, consider checking the power quality with an oscilloscope. You may be surprised at the ripple and noise they contain, and both can lead to crashes, damages or malfunctions.
Power wiring
The cable quality and current carrying capacity is an important factor when powering Pis due to the resistive effect of the cable material. This is the reason our Designed-for-Pi power supplies use non-removable cables; they use a thicker cable to reduce the voltage drop caused by current passing in it. I know high-quality USB cables are available elsewhere that meet this low-resistivity requirement, but they are more expensive compared to common USB cables. These high-quality cables are designed to reduce the impact of resistivity vs length by using thicker wiring for longer cables. I've tested some of them and they worked correctly with Pis in most cases.
In any case, I believe you can avoid resistivity issues by using 20AWG or larger copper wires. Of course, the wire size depends on the length of the cable and the current requirements of your project, so make sure to test them! It passes the test if you get at least 5.0V on the GPIO pins at full current load!
Troubleshooting
Monitor
A monitor is essential for debugging in many cases, especially if the goal is going without a monitor/keyboard/mouse attached (headless). Once you are headless, if the remote connection fails, a monitor is the only way you can know what happens on the Pi. Keep one handy, hope to never need it! You could also use a direct serial connection if you configured the Pi for debugging before you need it. More details are available here: https://www.raspberrypi.org/documentation/computers/configuration.html#configuring-uarts and https://www.raspberrypi.org/documentation/computers/remote-access.html
Baby steps
Don't test the project as a whole, do it step by step. Make sure the basics (Pi, monitor, power supply) work properly then add the card with the Operating System, then an accessory, etc. Add one or two small changes and test again. Doing so makes it much easier to find faults and negative interactions, each step is sitting on a known good step. If you don't test at every step while assembling a project and it doesn't power up, every part could be the problem and like a house without a solid foundation, it collapses! You would need to break everything apart to find the fault.
Pi4/Pi400 no-card boot
The Raspberry Pi 4B and Pi400 contain an EEPROM holding the firmware, unlike the other Pis. This allows the boot code to be more sophisticated, meaning that you can do a simple basic Pass/Fail test of your power supply, monitor and Pi 4 or Pi400 by booting it without a card. If the parts are correctly working together, you will see a "boot failed" screen showing some information about the failing boot process. Never underestimate the usefulness of testing a Pi4/Pi400 card-less (power, monitor, Pi4 only) to do a quick Pass/Fail test! You will know that the power supply provides electricity, the Pi works, and it talks to the monitor!
Note: if you are using an operating system that isn't Raspberry Pi OS, you may need to manually update the boot EEPROM code from time to time. Follow the "Updating the bootloader" instructions on the Official Raspberry Pi 4 boot EEPROM documentation page for details.
Conclusion
I hope these few tips will help you find and fix issues you are having or avoid them!
Don't hesitate to contact us if you need more help!
Revised 2021-08-25 - Link update for the RPF website restructuring