Choosing the right PSU and buck circuit to power SBCs - Page 1
Forum section: electronics / beginners

author: System Error Message
author_rank: Frequent Contributor
timestamp: February 15, 2023, 10:22:21 am
content: Hi im looking to power my SBCs via buck circuits and a common PSU but my experience with the usual metal case PSUs all around have been poor in reliability so i need help finding a reliable one. Only option for me are shops like aliexpress due to location. The other thing i want to do is to place 2 power supplies together in redundancy and connect with a battery similar to lead acid but with a compatible voltage so there wont need to be a controller or anything.Most of my SBCs run on 5V, and can power via GPIO or via DC jack. Im sick of usb charging hubs not providing reliable 5V at the amps they need despite supposedly being capable of way more and leakage of AC voltage which i have seen mess with boards before on PCs (like feeling a shock on the PC case). A lot of SBCs are strict on voltage they get while my networking gear operate with a large voltage range (12-48V). i also have case fans sitting around that are 12V. My goal is to place the network and SBCs small portable rack and all the associating gear and fans. I've calculated how many watts i need.My first problem is tackling the pairing of PSUs together, how do i safely pair them together? Do i need diodes to prevent current flow in the wrong direction? Do i only need a diode on + or both + and - outputs?For the choice of voltage between the PSU and buck circuit, the output voltage can be adjusted, would 12V or 24V PSU be better for efficiency down to 5V? in the event of a PSU failure 12V wont give much range for the network as 12V is on the lower end, but i heard that buck circuits operate best when the voltages are close together. My goal in using a buck circuit is that i need stable 5V. Using a similar PSU on my router it only started rebooting at 9V despite the PSU being 24V as it failed within months and the router being rated at 12V minimum (120W). The buck circuit im looking at can be tweaked between 2-30V i think so the highest voltage for some SBCs that are x86 based are 19.5V similar to laptops and while their power bricks work fine they do not work fine if i attach any drives to them so im still questioning whether or not to switch to the same setup for them.For network gear that accept a large range of voltages, there is no need to prepare any circuit for them so i can just directly plug the PSU into them. Battery is something i will deal with a lot later. If i want to monitor the voltage of the PSU, if paired even with diodes, is there an accurate way to check in order to check for failure?

author: MathWizard
author_rank: Super Contributor
timestamp: February 16, 2023, 06:49:30 am
content: I'm not sure what a SBC is, but if I was looking for well regulated 5V or 12V at many many amps, I'd use a good quality computer PSU (maybe even a low-end one would do). IDK what some industrial 5/12V supply would cost, but decent computers PSU's are fairly cheap, and easy to find.

author: System Error Message
author_rank: Frequent Contributor
timestamp: February 16, 2023, 09:28:13 am
content: single board computer like a raspberry pi. When powering them, they are voltage sensitive that instead of 5V you get 4. and it hangs. some have a voltage range like 9-15V. so using buck circuits let you avoid that and allows you to cater to different devices from the same source and not worry much about voltage accuracy. So instead of buying a 100A 5V PSU you could get a 24V 20A PSU for example which is usually a better option in many ways.Then pairing them up is another challenge, for PSUs anything to prevent backwards flow that could damage them, for buck circuits, their efficiency depends on the input voltage vs output voltage (not sure about this one).Since i have a range of voltage needs it just makes sense for me to power them all with just 2 as there will be less bulky plugs and rackmount power distributions are a let more decent than your regular power extensions in quality and space. I also have power outages so figuring out a compatible battery making my own our of recycled materials would be fun and keep my software running.Some of the wall warts and 5V PSUs i have arent great, and some of the SBCs i have dont run HDDs well because of it or because of the voltage out may just hang. WHile a phone can see the voltage drop and stop pulling more amps, SBCs dont have the same circuits and once the voltage is out of whack will just hang and stop working needing a reboot. So phone chargers and similar usb hubs allow a voltage drop but SBCs hate it.

author: Junaid_raza
author_rank: Contributor
timestamp: March 28, 2023, 06:16:29 pm
content: You can use diodes to stop current flow in the wrong direction when connecting two power supplies safely. On the positive and negative outputs, you'll need a diode. When choosing between a higher voltage PSU and a buck circuit, you can step down to 5V more effectively, but you must make sure the voltage is within the buck circuit's operating range.You can use a multimeter to check the output voltage and keep an eye on the PSU's voltage. To prevent electrical shock or short circuits, make sure the multimeter is adjusted to the proper voltage range and use caution when probing the PSU outputs.

author: Infraviolet
author_rank: Super Contributor
timestamp: March 28, 2023, 08:50:56 pm
content: Raspberry Pi branded microUSB wall warts are pretty good quality, supplies either 2A or 2.4A max at 5V. Depending what you need to power breakouts from microUSB to header pins are easy to find online.You mention buck circuits as well as PSUs, is that for battery powering? When I've put SBCs in battery powered things I've gone for pre-builtswitching regulator modules with substantially over-specced maximum currents. A Pi ran with no trouble on a 5A 5V step down switching regulator run from a 13V to 10V (as charge varies) battery. Pololu makes some good step-down switching regulator modules, and I think there are several UK sellers for some models.

author: shapirus
author_rank: Super Contributor
timestamp: March 28, 2023, 09:01:46 pm
content: I've had issues with OrangePi Zero (which is quite a low-power SBC) powered from a battery via a step-down (switching) converter that has a potentiometer for limiting current.Normally the OPi draws something around 400-500 mA, so one would imagine that pretty much any USB charger would do. Wrong. Even when the converter was set to 1A and, IIRC, 1.5A, the OPi failed to boot, and the indicator leds on the converter showed switching to the CC mode. I had to crank it up to 2A or even more, and only then it became able to start reliably. Apparently there are short high-current pulses somewhere during initialization. I tried adding a beefy capacitor, I guess 1000 uF or so, on the output of the converter, but it didn't help, it still went into the CC mode.So yes, a decent power source is required that can provide short bursts of higher current even when most of the time it's going to be low.

author: radiolistener
author_rank: Super Contributor
timestamp: March 28, 2023, 11:23:09 pm
content: Quote from: System Error Message on February 16, 2023, 09:28:13 amany PSU which fairly fits Amperage rating should works. Voltage may drop down due to a bad wires or bad contacts.