The buck converter solution seems reasonable. I was going to use similar in my microscale cloud prototype
Yep. Been using a recycled PC power supply to power multiple Pi's for years now. Some recommend fusing but I haven't bothered.
I admit I haven't bothered with fuses. Partly because I'm lazy but mostly because I've never seen fuses between PSU and motherboard/HDD/ODD/GFX cards/etc.
Yes, ATX PSUs have over-current protection. But the output will reach the full capacity of the rail you are using (maybe 50A or more) before the protection kicks in. A short under the Pi's PCB can cause a lot of damage before the PSU shuts down -- the tracks will not tolerate that level of current for long, compared with the time for which 3A is safe.thagrol wrote: All thsoe things can potentially short, with no inline fuses I assumed (correctly it turns out) that protection is inside the PSU.
heh.. Ive bought MeanWell RS-50-5 but having issues with USB connectors.. simply not good quality and not delivering enough so when all 4 USBs are in use I'm getting low power errors I'll try the GPIO pinsJMK8 wrote: ↑Tue Jun 30, 2020 11:12 amI use one of these...
https://www.amazon.co.uk/XKTTSUEERCRR-S ... 356&sr=8-2
Earth leakage breakers (sic) do NOT provide over-current protection.
A 200W 5V supply is at least 40A before the overcurrent kicks in. If you are using anything less than 10A (may be more) cable then there is a good chance that a short/fault at the end of that cable won't trigger the overcurrent protection. So regardless of damage to the pi, the cable is likely to set fire to your house - similar to certain 3D printers.
Fast-blow fuses designed for use in automobiles seem pretty cheap compared to a new house. Would a 3A fuse frompidd wrote: ↑Tue Jun 30, 2020 10:34 pmA 200W 5V supply is at least 40A before the overcurrent kicks in. If you are using anything less than 10A (may be more) cable then there is a good chance that a short/fault at the end of that cable won't trigger the overcurrent protection. So regardless of damage to the pi, the cable is likely to set fire to your house - similar to certain 3D printers.
Fuses other than those fitted on/in devices are not designed to protect devices, they are there to protect cables, they are a fire safety device.
Devices generally have thermal fuses in them to protect against overheating - again fire safety related protection.
So please stop thinking about protecting an already faulty device, use fuses to ensure your property and people don't end up as a charcoaled mess.
More or less agreed. 4A fuse if I could find one! The cable needs to be able to stand the short circuit current (way more than the fuse rating) for the time it takes the fuse to blow. Not usually a problem unless the short circuit current is limited (by the PSU or wiring resistance) to a smallish overload where the time to blow is long. Just use cable capable of something like 6A or 10A. The full calculation is foul: it's an adiabatic equation, because the cable characteristics vary as it heats up while carrying SC current. It requires knowledge of detailed cable and fuse characteristics and ambient operating temperature. It can be solved graphically. Details are in BS7454, or briefly in Wiring Regs (BS7671:2018) 543.1.3.