If you power through GPIO pins, you are bypassing the on board power protection circuits. At the very least, put a fuse (probably best to be a polyfuse) in your power circuit to protect against overcurrent conditions. To properly protect your Pi against power supply faults, you would need to--basically--replicate the power protection circuitry built onto the Pi.
Actually, for a Pi3B+, a polyfuse is all that is required to replicate the on-board protection. The perfect diode used on earlier models has been removed, and the TVS diode is not bypassed. Type MF-MSMF250/X or equivalent.W. H. Heydt wrote: ↑Sat Apr 13, 2019 4:47 pmIf you power through GPIO pins, you are bypassing the on board power protection circuits. At the very least, put a fuse (probably best to be a polyfuse) in your power circuit to protect against overcurrent conditions. To properly protect your Pi against power supply faults, you would need to--basically--replicate the power protection circuitry built onto the Pi.
You could easily add a 2.5A solid state fuse, maybe try a google for this or look for alternativesNoel_g wrote: ↑Sat Apr 13, 2019 3:20 amI am new to RPI and have basic understanding of electronics so I want to make sure I am doing things right.
My project is a Sprinkler valve controller. I have learned that those solenoid run at 24VAC so I am getting this power supply.
Orbit Sprinkler System Power Source Transformer 57040 https://www.amazon.com/dp/B000VRYVYS/re ... RCbHA0RP4B
It seems redundant to get a 5V power supply to power the RPI so I am also getting a power converter.
SMAKN® DC 5V/3A(MAX) AC/DC TO DC Buck Power Converter Voltage Step Dowm Power Supply Waterproof Input AC 7-36V/DC 8-50V https://www.amazon.com/dp/B00RE6QN4U/re ... RCbN8CFQ47
My question is as follows. I plan to apply power to the RPI via the GPIO. Do I need to add anything in between the converter and the GPIO for protection? The converter can output up to 3A so I don’t know if that’s a problem.
That solves the fuse problem but you must make sure the wires are thick enough (18 AWG) -- this applies to power connections via the GPIO header too. Most USB cables have much thinner wires, you need one designed for charging at 2-3A.
Actually micro usb.
Why not use something like this?
Yeah "If the buck converter is situated close to the RPi , AWG18 should not be necessary" as for a long time now it has really perplexed me how all pi PSU are extremely bad by just cable design and there seems to a a total lack short run DC figure8 mains power for the Pi.drgeoff wrote: ↑Sun Apr 14, 2019 12:23 pmThin wires are only a problem if they are long.
https://en.wikipedia.org/wiki/American_wire_gauge says for copper wire
AWG18 about 20 milliohms per metre
AWG22 about 50 milliohms per metre
AWG28 about 200 milliohms per metre
So 1 metre of AWG18 or 40cm of AWG22 or 10 cms of AWG28 all drop the same voltage when carrying the same current.
For a 3B+ at max 2.5 amps those lengths would drop 0.1 volts maximum. (The current passes through 2 lengths.)
If the buck converter is situated close to the RPi , AWG18 should not be necessary.
Try searching for the following:
Oh yes I had found a few of those but then I read reviews and people mentioned how hard it was to solder to those little terminals. I am going to try my original idea of cutting a cable and soldering right to those wires.
I take my prior reply back I did a search and found this. Seems to be a good option.
LTolledo wrote: ↑Tue Apr 16, 2019 10:15 pmHow many solenoids (and their power requirements) are you planning to activate with your setup?
the linked AC power source (as I see it) is rated at max 750mA
that 750mA will have to be shared by the solenoid(s) and the buck converter powering the RPi3B+
activating a single solenoid may introduce sufficient power transients to your system, the more solenoid there is, the worst it might get.
For better system stability, powering the RPi3B+ with separate AC mains PSU (no chargers please) 5v 2.4A is my recommendation.
The solenoid(s), deriving power from the 24V AC source, will be activated by the RPi3B+ via a [relay/SSR board -- transistor/transistor module] combo.