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

 

Patience maties.   Don’t knock anybody making a product which is pretty much exclusively for ham radio ops.  Hams are NOT that great of a market place.  We need all that we can get.  

The DRAWS is pretty cool if you want to be doing APRS stuff with Direwolf.  

I acknowledge that it doesn’t address the 12v backup power thing we’ve been talking about.  
This is my wishlist for a Raspberry PI backup and power control system:
  • Runs a Raspberry PI 3B, 3B+ or 4B @5.1vDC 
  • It is powered by a 11.5vDC to 15vDC mains/primary power source.  
  • Powered using Anderson PowerPole connection.
  • Provides backup power to the Raspberry PI with instant switchover if the primary power source goes below 11.5v (maybe configurable?)
  • It should have an on/off button or toggle to do a safe shutdown of the Raspberry PI.  
  • It should know if we turned off the PI using an external switch, that the PI should stay off until we turn it on, even of the main power and secondary power are removed and re-applied.   A toggle switch input is ideal for this since it has a real “OFF” state. 
  • Uses an unspecified battery for backup power, given some reasonable battery voltage (6.5v to 15v?).  
  • Supports an unspecified external charger for any particular battery and can remove the charger from the circuit when the battery is discharging.  
  • It should be configurable to do a self-declared Raspberry Pi shutdown if the battery backup battery goes below the configured voltage, and then return the Raspberry PI to powered-up only if the mains/PRIMARY source is present for a configured length of time. 
  • It should be able to tell us how l long the power was off for, and let us read the voltage of either mains/PRIMARY or battery input in real time.
  • It would be nice if it could log the voltage on each power input periodically whenever the switch is ON, regardless of whether running on primary/mains or battery.  Perhaps the log would increase the time between readings logarithmically if it runs out of memory space?  
  • It should have some RF immunity features built in, including ground-plane, a large tinned-thru-hole screw-hole for #4 screw to ground the unit, and maybe provision to insert ferrite beads and bypass caps in off-the-board circuits?  
  • It should be almost free (haha)
There aren’t many points not covered by the MOPI.  

I’m not particularly wedded to having a shield card/hat for a Raspberry PI.  I find the physical mounting of such units to be sloppy and access to switches, variable controls, and LEDs on stacked boards is difficult.  I’d prefer using a 6” USB cable, but I acknowledge the additional expense and in-circuit loss of such a thing.  
   Tadd / KA2DEW
   Raleigh NC




On Dec 30, 2019, at 12:30 PM, Daniel Holmes <danielh@...> wrote:

Eh, considering all that it does and the convenience factor I don’t think $150 is all that outrageous. I already have a Pi-TNC, Signalink, GPS puck, and the Mo-Pi, so it’s superfluous for me. The Mo-Pi handled my power requirements (namely multiple inputs and charging circuitry) better than the DRAWS HAT. Although it would be very convenient to have everything in one package.

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


On Dec 30, 2019, at 10:22 AM, Michael WA7SKG <wa7skg@...> wrote:

Thanks for the suggestion, but I am not going to spend another $150+ for more hardware that is less capable than what I already have to do the work of a $7 buck-boost module.

Michael WA7SKG

John D Hays - K7VE wrote on 12/30/19 8:48 AM:
For Amateur Radio use, be sure to look at the DRAWS™ <http://www.nwdigitalradio.com/draws> board: 9-15 VDC input supply, sound card, dual radio interfaces, GPIO pin extensions, GPS (w/battery backed clock) -- all integrated into a Raspberry Pi HAT.
http://nwdigitalradio.com/shop/
--
John D. Hays
Kingston, WA
K7VE








 

Not, yet, interested in 1200 baud, especially at $150.
The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle. In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.

DRAWS has suggested it will work at 19,200 but I'm waiting for them to
demo that - preferably with iPerf numbers...

Bill

Ed K6ESS
 

Tad came pretty close to a "Santa's wish list" card. I could pass on all the data logging, but all else is spot on. Santa, can you come thru with a late Christmas gift?

Ed K6ESS
Sacramento CA

Make everything as simple as possible,  but not simpler.  Albert Einstein

On Tue, Dec 31, 2019, 16:14 Bill Vodall <wa7nwp@...> wrote:
> Not, yet, interested in 1200 baud, especially at $150.

The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle.  In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.

DRAWS has suggested it will work at 19,200 but I'm waiting for them to
demo that - preferably with iPerf numbers...

Bill



Michael WA7SKG
 

"the Signalink will not work at the higher speed because it has transformers in the audio chain."

Huh?? It is audio. Maybe a greater bandwidth due to the speed, but audio nonetheless. Entertainment system audio often goes over 15 kHz through transformers. I would be interested in understanding why the Signalink cannot do the higher speeds because it has transformers. I always like to learn new things.

Michael WA7SKG

Bill Vodall wrote on 12/31/19 4:13 PM:


The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle. In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.

Daniel Holmes
 

It’s always been my understanding it’s not the transformers that are the problem, it’s where the audio is injected—if it’s injected in the mic input then you are limited to 1200 baud, but if you inject elsewhere (the IF? I can’t remember) the you can get 9k6. A lot of modern radios have inputs for data that take 9k6. I think any soundcard can connect to those inputs for higher baud rates via direwolf. The signalink and other specialized cards I think have optical isolators that isolate from the computer. ‘Course it is NYE, and I could be all wrong due to that. 

Dan

--
. Please pardon any mispelings or errors.


On Dec 31, 2019, at 8:48 PM, Michael WA7SKG <wa7skg@...> wrote:

"the Signalink will not work at the higher speed because it has transformers in the audio chain."

Huh?? It is audio. Maybe a greater bandwidth due to the speed, but audio nonetheless. Entertainment system audio often goes over 15 kHz through transformers. I would be interested in understanding why the Signalink cannot do the higher speeds because it has transformers. I always like to learn new things.

Michael WA7SKG

Bill Vodall wrote on 12/31/19 4:13 PM:

The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle.  In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.



Ray Wells
 

In simple terms 9600 is not audio tones, it's a data switching rate (actually at 4800 and doubled in the process) . For 9600 the frequency response of the signal chain is ideally down to a DC response which of course won't pass through a transformer. One of the "fathers of 9600 packet was James Miller G3RUH who produced various modems. His writings on 9600 are worth a read for some detail about what works and what doesn't. Try this for starters https://www.amsat.org/amsat/articles/g3ruh/109.html

HTH
Ray vk2tv

On 1/1/20 3:02 pm, Daniel Holmes wrote:
It’s always been my understanding it’s not the transformers that are the problem, it’s where the audio is injected—if it’s injected in the mic input then you are limited to 1200 baud, but if you inject elsewhere (the IF? I can’t remember) the you can get 9k6. A lot of modern radios have inputs for data that take 9k6. I think any soundcard can connect to those inputs for higher baud rates via direwolf. The signalink and other specialized cards I think have optical isolators that isolate from the computer. ‘Course it is NYE, and I could be all wrong due to that. 

Dan

--
. Please pardon any mispelings or errors.


On Dec 31, 2019, at 8:48 PM, Michael WA7SKG <wa7skg@...> wrote:

"the Signalink will not work at the higher speed because it has transformers in the audio chain."

Huh?? It is audio. Maybe a greater bandwidth due to the speed, but audio nonetheless. Entertainment system audio often goes over 15 kHz through transformers. I would be interested in understanding why the Signalink cannot do the higher speeds because it has transformers. I always like to learn new things.

Michael WA7SKG

Bill Vodall wrote on 12/31/19 4:13 PM:

The DRAWS board is designed for 9600 baud which most other sound card
interfaces won't handle.  In particular, as handy as it is, the
Signalink will not work at the higher speed because it has
transformers in the audio chain.




Eric
 

I think I remember reading that 9600 bps requires DC coupling to the modulator.

Transformer coupling would be a problem if that is the case.

Eric
WB6TIX

On Tue, Dec 31, 2019, 20:48 Michael WA7SKG <wa7skg@...> wrote:
"the Signalink will not work at the higher speed because it has
transformers in the audio chain."

Huh?? It is audio. Maybe a greater bandwidth due to the speed, but audio
nonetheless. Entertainment system audio often goes over 15 kHz through
transformers. I would be interested in understanding why the Signalink
cannot do the higher speeds because it has transformers. I always like
to learn new things.

Michael WA7SKG

Bill Vodall wrote on 12/31/19 4:13 PM:
>
> The DRAWS board is designed for 9600 baud which most other sound card
> interfaces won't handle.  In particular, as handy as it is, the
> Signalink will not work at the higher speed because it has
> transformers in the audio chain.
>



Michael WA7SKG
 

And yet the previously referenced article ( https://www.amsat.org/amsat/articles/g3ruh/109.html) says:

"One is that the channel is not DC coupled. It could never be so in an FM system unless one could guarantee both transmitter and receiver were always exactly on frequency and had no drift. As this is virtually impossible to achieve, one simply AC couples the channel, i.e. gives it a response down to a few Hz, and exploits the feature of the randomised data that it has a negligible DC component."

I always thought AC coupling was often via a transformer.

That's okay, I'm a native of the State of Confusion.

I'll crawl back under my rock now.

Michael WA7SKG



Eric wrote on 12/31/19 8:31 PM:

I think I remember reading that 9600 bps requires DC coupling to the modulator.
Transformer coupling would be a problem if that is the case.
Eric
WB6TIX
On Tue, Dec 31, 2019, 20:48 Michael WA7SKG <wa7skg@... <mailto:wa7skg@...>> wrote:
"the Signalink will not work at the higher speed because it has
transformers in the audio chain."
Huh?? It is audio. Maybe a greater bandwidth due to the speed, but
audio
nonetheless. Entertainment system audio often goes over 15 kHz through
transformers. I would be interested in understanding why the Signalink
cannot do the higher speeds because it has transformers. I always like
to learn new things.
Michael WA7SKG
Bill Vodall wrote on 12/31/19 4:13 PM:
>
> The DRAWS board is designed for 9600 baud which most other sound card
> interfaces won't handle.  In particular, as handy as it is, the
> Signalink will not work at the higher speed because it has
> transformers in the audio chain.
>