Re: 12V Power for the Pi (was Re: [RaspberryPi-4-HamRadio] Getting back to the RPi)


A basic solution would be to just let the mains be online for some period of time before you let the Raspberry PI start.  That period of time could be configured based on charger and battery chemistry I guess.

I'm also interested in it NOT bringing the Raspberry PI up if the last time the operator played with it they left it shutdown.  That would require the charger controller CPU keeping track in RAM or in NVmemory of some kind. 

I made a charge/backup management device with these features but it didn't have provision for an external charger, it only had a trickle for SLA batteries, and it didn't put out enough volts for the Raspberry PI 4.  It used a fixed 5V USB regulator, and worse, it had a USB A socket for a cable to go over to the Raspberry PI.  For a modern Raspberry PI we want 5.1 or so and that voltage AT the Raspberry PI. 
I think PWRMAN has been abandoned because of the low voltage output.  One of the TARPN people was working on a new PCB which was a hat for the Raspberry PI but other things came up. 
 Tadd KA2DEW

On December 24, 2019 at 2:50 PM, David Lane <kg4giy@...> wrote:

By default, yes, once there is enough power, the boot cycle starts. 

Question - how would you retard the boot cycle, until the battery fully charges? Or are you assuming that once the mains are back up, you are ‘good to go,’ and not worried about a secondary outage without enough battery? If the MOPI is managing the battery, does it have the ability to retard that restart?  (I am thinking about the much larger logic circuits that are in smart ups and larger power systems that keep the main CPUs from coming back if the battery charge is still insufficient for full operations and shutdown again - then you get into a is there enough capacity in the capacitor for the battery to know if the capacitor is charged enough to tell the battery to start charging again). Or does it not really matter? (Worse case scenario is a required FSCK on the drive preventing a boot and needing a manual intervention). 


On Dec 24, 2019, at 2:34 PM, Daniel Holmes <danielh@...> wrote:

I don’t have it handy to check, but I’d assume so—anytime you remove power from a Pi and then reapply power it starts up. 


. Please pardon any mispelings or errors.

On Dec 24, 2019, at 11:41 AM, Tadd KA2DEW in NC via Groups.Io <tadd@...> wrote:

interesting.  ok.  so same scenario but in B> the Raspberry PI is left OFF.  Does it turn on when G or H? 

On December 24, 2019 at 1:36 PM, Daniel Holmes <danielh@...> wrote:

If power is applied to the Pi while it is off it will turn on at G.

Daniel Holmes, danielh@...
"Laugh while you can, monkey boy!" -- Lord John Whorfin

On Dec 24, 2019, at 11:33 AM, Tadd KA2DEW in NC via Groups.Io <tadd@...> wrote:

Using the MOPI-2 In this scenario

A> mains are working.   
B> Start Raspberry PI
C> runs steady for a long time (weeks) 
D> Mains go to 0v but are still hooked up.
E> battery eventually gets low
F> MOFI does LInux shutdown and turns off Raspberry PI
G> mains come back eventually
H>  battery charges 
J> raspberry is provided power again 

Is there a way to have the Raspberry PI come back on-line in H or J ?   

  Tadd - KA2DEW 
  Raleigh NC USA

On December 24, 2019 at 11:39 AM, Daniel Holmes <danielh@...> wrote:

Good question on a monitor—I think the specs said it’ll only do about 2.5-3 amps, but there’s a way to switch in a 5V relay to power up the monitor. I personally run my Pi headless, and use VNC on my iPad to connect in (although I have a small wireless keyboard I use because typing on a virtual keyboard stinks.)

Daniel Holmes, danielh@...
"Laugh while you can, monkey boy!" -- Lord John Whorfin

On Dec 24, 2019, at 9:35 AM, Michael WA7SKG <wa7skg@...> wrote:


THANK YOU! What a device! While you say expensive, it's only a few dollars more than the USBuddy and does so much more. The on/off switch is a big plus, as well as the HAT configuration. The only thing I'm not sure of is powering the monitor as well. As I am using the Smarti-Pi Touch Case, the RPi is not mounted directly to the monitor, so it is not powered through the IO pins, but from a separate USB connection. However, I do not think this is insurmountable.

Thanks again.

Michael WA7SKG

Daniel Holmes wrote on 12/24/19 6:57 AM:
For running off a 12V supply, this is what I use: Seems to be pretty RF quiet.
Yeah, it’s a bit expensive, but I have it wired with an on/off switch to power up/power down the Pi cleanly, and it powers it down when the batteries are almost exhausted. I haven’t worked up the battery charger just yet, but it’ll be a handy part of my go-kit. I still need to figure out how to use more than 1 HAT on my Pi, but that’s just a bit of research—so many projects so little time.

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