Re: Noisy Pi4 - particularly on 2m


Indeed.  $140 is a non-starter.  
It would be idea to be able to fully discharge the battery once in a while with a constant current load while watching the voltage.  This could give us the true capacity.  However..  For $3 worth of parts we can float a gel-cel across a 13.7v supply through a 47 ohm 10watt resistor and that does the job within the Gel Cel survival tolerances specified by the UPS manufacturers, i.e. about 3 years to replacement.  The real value in the $140 device is that it saves the Gel Cel from damage as it passes through the not-recoverable-voltage.  But we can do that with a zener diode, a transistor and a relay.  What we’d really like is two Zener diodes where the higher voltage one would be used to send a logic signal to the Raspberry PI telling it that it is in danger of losing power soon.  I don’t think the $140 device does that.  But we can make a circuit that does, put all fo the switchover and charging parts along with the zeners, relay and whatnot onto a PCB for about $15.  
now.. toss in a DC in 5.1v DC out 3amp regulator with a USB-A socket and we have a real product.  $140?  How about if we sell the PCB for cost and let the operator build the kit from Digikey purchased parts?  $40.  There you go.  My thought processes in a nutshell.  

   Tadd - KA2DEW

On Jun 3, 2020, at 3:15 PM, Mark Griffith via <mdgriffith2003@...> wrote:

If you want battery backup, you need to have some sort of charger to manage the battery.  This is much more than just providing 12v power.  The PWRGate switches instantly from the power supply to the battery, not causing a Raspberry Pi reboot.  This is the most important thing to me to prevent premature SD card failure.

You can also try putting a battery maintainer as sold in Walmart and other stores that supply 1.5A at 12VDC, and attach that to a battery, and then your 12VDC to microUSB power module.  This works, I have done it in the past, but they are not very good at keeping the battery charged AND supply power to a Raspberry Pi and radio.  The battery eventually looses its charge and you don't find out about it until the power fails and your Raspberry Pis go down.  The PWRGate integrates all the parts.

You are, of course, free to design your own.  There are lots of plans online for voltage converters.


On Wednesday, June 3, 2020, 1:30:46 PM CDT, Tadd KA2DEW in NC via <tadd@...> wrote:

The wet mount radio power gate costs $140??  
And I thought $40 was high. And the battery protection and charge is just one minor feature of the $40 project. 
$13 EACH to try some and see what happens.  Hmm..   

What I’m hearing is that there isn’t really a product out there that gives us the 5.1v from 12v every time one is bought and tried.  
The little wall wart thing for the Raspberry PI 4 is a good thing, but it has the wrong voltage input and no battery backup. 

On Jun 3, 2020, at 2:26 PM, Mark Griffith via <mdgriffith2003@...> wrote:

There are lots of these modules around, some are better than others.  I have used some that output 5.15 volts consistently, and some just 5.0 volts.  Some have two micro USB connectors, some do not.  I have a few of these I use now that are very reliable.  eBay is a good place to find them.

I guess for $13 you get some and see what happens.  You can also afford to get a few as backups in case of failure.

In my shack, I use a West Mountain Radio PG40S power gate which takes 15 volts from an old Radio Shack analog power supply, and outputs about 14.8 volts to a Anderson Power Pole power block, and keeps a Type 27 deep cycle battery charged.  From the power block I use a few of these DC-DC step down modules to convert to 5.1 volts.  I have the same setup at my home (shack is in a different location) with a smaller battery to power the PiGate development devices and a radio.  If the power fails, the battery is switched in instantly and give me enough power to supply my PiGate RMS station for a day or so, or my home development site for about 12 hours.

There are lots of solutions.  Experiment!



On Wednesday, June 3, 2020, 12:29:02 PM CDT, Tadd KA2DEW in NC via <tadd@...> wrote:

What we need is a 9 V to 15 V DC input device which outputs 5.1v regulated to a USB socket and which delivers that voltage reliably automatically when the input voltage is applied (not like the new DROK device which requires menu manipulation to turn on the USB output).  Most of the devices that are close to these specs only put out 4.9 to 5 V which is not enough for the PI 4B.  Or, they use screw terminal outputs which is not good for the casual Raspberry PI software engineer.  Sockets are good.  
We’d further like this device to be $20 or less.  I’ve seen things which are really close to what we want for as little as a couple of dollars.  But close doesn’t count here.  It has to be 5.1 VDC and it has to be always on, and it has to take DC input.  

Would it be worth $40 to have a 3 Amp linear supply through-hole KIT that does the above?  I have a schematic for a circuit to do this and handle charging, switchover, and relay protect for a GelCel UPS and early protection alert to Raspberry PI when the battery is getting close to damaging itself.  WN8P did the schematic.  We’re pondering making and selling PCBs (for cost via ETSY) and publishing a bill-of-materials for builder purchase from DigiKey.  

The design seems expensive.  I’m just wondering if it is worth it.  The cost includes the heat sync but no housing or Gel Cel.   Dunno.  It seemed a good idea at the time.  I can do really good kit building instructions. See this page: 


On Jun 2, 2020, at 8:33 PM, Chuck M via <cam51mail@...> wrote:

I've done that as well.  On pi3 tweaked the voltage until lightning icon stayed home.

Thingiverse has various case designs for them depending on model.  Also designs to make inline fuse holder.

Can also get something like this:


On Tue, Jun 2, 2020 at 7:34 PM, nb7o
<khedgepe@...> wrote:

Another solution, that I use here, is to buy a dc-dc voltage converter.  I have a 12v to 5v dc-dc converter with a usb connector on the 5v side.  I have Anderson power poles on the 12v side and I plug it into my 50a 12v power supply.  The DC-DC converter I have provides 3a of power to the PI which also helps with low voltage conditions on the pi.


Seven three de kevin/NB7O

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