Power Pi4B via Einsy?
Cross-posted from the "Other" forum.
Hooked up a 4B to my MK3S per the following (which is the same as the Pi Zero layout and what people seem to be doing):
Got everything running but OctoPrint doesn't like the 2.5A underpowered state.
Before anyone asks, the reason I'm pursuing this is that the idea of 2 separate power cables to 1 device (the printer, overall) is fundamentally wrong/unrefined in my mind.
Now, I know I can loop in a buck converter at 5V 3/5A from the PSU, or more aptly the power rail on the Einsy, but that seems too hacky.
I am pretty amateur on electronics but I know a decent amount. The J19 RPi header is delivering 5V 2.5A to the Pi via VCC pin 2. 
What are the implications of connecting VCC pin 10 to the currently unused pin 2 (+5V) on the Pi? The Pi specs say 5A is OK.
Additionally, would I need to add another ground? I would think so because somewhere I saw either the GPIO or J19 are only rated for 3A. It was speculated in another post that the J19 Pin-14 which connects to GPIO 23 is actually unused and only for structural integrity with the Pi Zero. Could swap that out if necessary. Anyway, hope someone who knows more than me can chime in.
RE: Power Pi4B via Einsy?
I read a lot about power issues with the Pi to my mind and backed up by testing the issue is often not the lack of available current but not enough voltage. 5.1V is required by the newer Pi’s. So a buck converter is the way to go. I’m using these powered direct from the 24V supply. One is dialled in at 5.1V for the Pi and one at 12V for LED lighting. They are the size of a stamp and quite efficient so don’t get to warm unless pushed
RE: Power Pi4B via Einsy?
the issue is often not the lack of available current but not enough voltage. 5.1V is required by the newer Pi’s.
But these are VERY related. Example. What happens when something tries to draw 2.5 A from a 2A power source? Most often it if voltage sag, so as the current approaches 2.5A, the voltage will start dropping from 5V to something else. That isn't always the case, sometimes the device will overheat and burn up, or protect itself or turn off. But, the common behavior when you pull more than the rated amps from a device is that the provided voltage will lower. People often describe a power source as being "stiff" if the voltage doesn't sag at all or very much near its rated current.
RE: Power Pi4B via Einsy?
Hi krb,
You are spot on. And the datasheets quote 5V but often all that is needed is a little voltage headroom.
I've built quite a few RPi based projectes over the years and often the current consumption is nowhere near the quoted maximum's. Quite often the only way to get there is to add power hungry periperals, screens, USB devices etc. or of course overclocking.
The thing with the Pi is that its voltage monitoring circuit is very sensitive and depending on how you introduce the power, cables and connectors can have a big influence. I'm not a fan of the micro USB connector for power. The pins are small, add a bit of dirt/corrosion and some very small conductors as used in poor cables and theres the voltage drop you state.
A lot of people are aware of the current requirement and make alloweneces but then wiring or poor regulation in the supply let them down.
As an example I have a RPi running as a media streamer with a DAC hat that was running on a 2nd gen Pi. It had twin supplies, one for the digital (Pi) and one for the audio (DAC) ran fine for years. Recently I upgraded the Pi and started to get the power indicator to pop-up. There were no operational issues and measuring the current consumption showed nothing that the PSU couldn't handle it was down to the voltage drop and that was with solid wiring direct to the board. In this case I swapped out the supply for a small 5V open frame PSU that I could adjust. Dialled up to 5.1V and the nagging indicator was gone.
Using a little PSU like the one I mentioned takes the load off the Ensiy board. You still have to consider the overall consumption from the main 24V PSU though.
RE: Power Pi4B via Einsy?
I have not had a single issue and have been running it for 12 months.
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Chuck H
3D Printer Review Blog
RE: Power Pi4B via Einsy?
For several years of my OctoPi setup, I've never saw a problem feeding a RPi 3B power via the micro USB, as long as the thing providing 5V was stiff enough. I've used the HobbyWing UBEC-3A in a variety of projects, because they've been more reliable for me at their rated limits. For the Octoprint RPi I replaced the wire with I 18 or 20AWG just to reduce voltage drop.
A few months ago, I wanted to control the power to the printer via the RPi, so I moved to an enclosure that has a MeanWell RS-25-5 (it's overkill, but it was in stock, I was impatient, and it was only $2 more than the RS-15-5) and a relay hat for the RPi. To keep the enclosure small, it doesn't have room to power via micro USB, so I ran power directly to the RPi header via 20AWG, and like you, I adjusted the voltage on the PSU so that it was a hair over 5V measured at the RPi when under load and connected to the Einsy.
Now to answer your original questions. A little searching makes gave mixed results on whether RPi Zero headers on Einsy board are capable of supplying enough current at 5V to power an RPi 3 reliably.
This says no:
https://www.thingiverse.com/thing:2840520
This seems to say yes:
https://www.thingiverse.com/thing:3289419
This thread on PrusaForums talks about the issues:
https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-others-archive/connecting-raspberry-pi-3-to-einsy-headers
RE: Power Pi4B via Einsy?
I'm working with the Pi3B+ and an external PS "Meanwell Ps-15-5" since over two years and never had a problem with undervoltage or other failures. (installed 3 cams, a touchscreen und a keyboard, some relais, set the Meanwell to 5.2V). I printed a case for the Pi and the PS and mounted it on the Frame -> https://www.thingiverse.com/thing:3289419
The 24V Prusa PSU is running sometimes on it's limit (nozzle and bedheating simultaneously) and therefore i would not connect a 24/5 converter for the Pi.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Power Pi4B via Einsy?
The 24V Prusa PSU is running sometimes on it's limit (nozzle and bedheating simultaneously) and therefore i would not connect a 24/5 converter for the Pi.
Sage advice.
RE: Power Pi4B via Einsy?
...it is also problematic to simply switch off the Pi with the printer. I switch the printer off via the Pi and then shut it down properly. This can significantly increase the life of the Pi-SD card.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Power Pi4B via Einsy?
@karl-herbert
It can be. I have a Streamdeck with buttons and I have a button for each pi so I can quickly shut them down before turning off the switch.
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Chuck H
3D Printer Review Blog
RE: Power Pi4B via Einsy?
The 24V Prusa PSU is running sometimes on it's limit (nozzle and bedheating simultaneously) and therefore i would not connect a 24/5 converter for the Pi.
Sage advice.
I did do this for a while to power a 3B. But PSU ticking, house light flickering, and wanting to add what turned out to be 7W of LEDs is what pushed me into upgrading the PSU to MeanWell LRS-350-24V.
RE: Power Pi4B via Einsy?
MeanWells are a good choice, used them in alsorts of solutions and can be trusted unlike a lot of the clones on your favorite auction site
RE: Power Pi4B via Einsy?
...it is also problematic to simply switch off the Pi with the printer. I switch the printer off via the Pi and then shut it down properly. This can significantly increase the life of the Pi-SD card.
I use relay, controlled by Pi. In Pi's command screen (OctoDash) i hit "shutdown" and Pi shuts down itself and at the end it also shuts down relay. It can be done simply by inserting this line in config.txt:
dtoverlay=gpio-poweroff,gpiopin=27,active_low=1
This will cause GPIO27 (pin 13) going LOW to do a shutdown and HIGH at power-up. You must only bypass relay contacts (with pushbutton, switch...) for a couple of seconds, long enough for relay to trigger, that's all.
I wouldn't power Pi via printer's 5V... i guess it's too stresfull for build-in regulator. Small buck converter does the job just fine.
Power-off button can also be made by inserting this line:
dtoverlay=gpio-shutdown,gpio_pin=7
GPIO27 (pin26) will indicate the pi is running when: HIGH if active_low=1; LOW if active_low=0
RE: Power Pi4B via Einsy?
Sorry, i messed up two commands.. correct is this:
power of button:
dtoverlay=gpio-shutdown,gpio_pin=7
This will cause GPIO7 (pin 26) going LOW to do a shutdown;
relay pin:
dtoverlay=gpio-poweroff,gpiopin=27,active_low=1
GPIO27 (pin13) will indicate the pi is running when: HIGH if active_low=1; LOW if active_low=0
RE: Power Pi4B via Einsy?
Before anyone asks, the reason I'm pursuing this is that the idea of 2 separate power cables to 1 device (the printer, overall) is fundamentally wrong/unrefined in my mind.
For me the printer and RPI are two different and separate devices. The one is always on (to get the updates and control the printer) and the other one is executing the tasks/prints.
Your setup is pushing the hardware out of specs. The einsy voltage regulator (LM25011MY) data sheet is saying:
| Current - Output | 2A |
|---|
This is for everything connected to 5V. Means your setup might work under certain conditions but you shorten the live span of the components and risk instability/hardware failure. I wouldn't recommend it.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Power Pi4B via Einsy?
@nikolai-r
i agree 1000% 👍
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Power Pi4B via Einsy?
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Power Pi4B via Einsy?
These cables make it easy!
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Chuck H
3D Printer Review Blog
RE: Power Pi4B via Einsy?
@charles-h13
Of course you can also buy this finished product, but you can also easily build it yourself. In the beginning I used a self assembled ribbon cable as an alternative.
something like this one: https://www.amazon.de/14-polig-2-54mm-Steigung-Buchse-Flachband/dp/B012SPRYMG
what I would not recommend due to lack of stability are these jumper wires: https://www.amazon.de/Aukru-20cm-female-female-Steckbr%C3%BCcken-Drahtbr%C3%BCcken/dp/B00OL6JZ3C
I only use them on the plug-in board for experimental purposes.
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.
RE: Power Pi4B via Einsy?
@karl-herbert
True. It is not worth my time and that cable is very professionally done with a great protective sleeve.
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Chuck H
3D Printer Review Blog