battery power for PocketBeagle?

[Shannon Mackey]

I expect I'm overlooking something, But it isn't obvious to me how to power the PocketBeagle with batteries.  It doesn't have a similar arrangement to BBB.  Can someone point me in the right direction, please?  Thanks!

[wi...@geomonkey.com]

I, too, am interested to know this. Wondering what the nominal and max. voltages are for SYS VIN and BAT VIN. Also, what sort of temperature sensor gets hooked up to BAT TEMP.

-- Will

[Graham]

P2 pins 14 and 16 ?

--

[Adam Saenz]

Pin 14 is the positive input for a single cell lithium (lion/lipo) battery.  Data sheet lists max input of 7V so you could use other battery combinations/chemistries if you like, but the internal circuitry will protect based on a single cell lithium.

Pin 16 is for a temperature sensor used for battery charging.  From the data sheet:

Temperature sense input. Connect to NTC thermistor to sense battery temperature. Works with 10k and 100k thermistors.  

I attached a snapshot showing the battery charge/temp sense circuit.

[Shannon Mackey]

Thank you very much!  The voltage limit was a concern. 

- Shannon

From: ajs...@gmail.com Sent: November 10, 2017 12:54 PM To: beagl...@googlegroups.com Reply-to: beagl...@googlegroups.com Subject: [beagleboard] Re: battery power for PocketBeagle?

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[Adam Saenz]

Keep in mind that the 7V is Absolute Max voltage so you should operate below this level or risk damaging the chip.

[wi...@geomonkey.com]

Adam --

Great, thanks for the info!

BTW, would you provide a link to the data sheet?

-- Will

[Adam Saenz]

Here is the link to data sheet:  http://www.ti.com/lit/ds/symlink/tps65217.pdf

Remember that this TI power management IC is integrated into the Octavo Systems part so that is why the data sheet is from TI.

Adam

[wm.ba...@gmail.com]

Adam --

This data sheet will be very useful. Thanks for sharing it!

Sincerely,
-- Will

[markus....@googlemail.com]

So if I connect Vbat (LiPo) to pin 14 I should expect the PocketBeagle to run, shouldn't I? (And obviously connect GND.)

With the PocketBeagle I have nothing happens. (I even put a 10k resistor as a mock NTC.)

[Adam Saenz]

Yes, Pin 14 of the P2 Header.  If you connect to Pin 14 of the P1 header you could have damaged your chip; that pin is connected to the 3.3V bus.

See section 7 (7.1.2 specifically) of the reference manual linked below.

https://github.com/beagleboard/pocketbeagle/wiki/System-Reference-Manual#Figure_24_PocketBeagle_Expansion_Headers

[Markus Mayer]

That's exactly what I did. (And I'm certain I didn't mix up P1 and P2.) I checked everything about ten times - there's not much to do: One battery, two pins...

But nothing happens.

Does this work for you??

[Johan Lind]

I just tried this and it works for me.
Battery plus to P2.14 and gnd to P2.15 (make sure you don't use P2.16, that's not batt gnd it's temp sensor input).
Press power button on board and it starts (it does not auto boot like when connecting to USB).

Where did your 10k resistor go (P2.16 and gnd)?

The board draw about 300mA at 3.8V when I tried it.

[Markus Mayer]

Oh I see... I thought I tried with the push button, but apparently I didn't. Yes, that works!

So, when pushed, the power button connects T11 on the SiM to GND. T11 is PB_IN of the TPS65127. PB_IN is the push button monitor (§8.3.3 of the datasheet rev. J):

"The push-button monitor has two functions. The first is to power-up the device from the OFF or SLEEP state when a falling edge is detected on the PB_IN pin. The second is to power cycle the device when the PB_IN pin is held low for more than 8 s."

I see up to 300mA draw when booting, then about 200mA when idling.

[Shannon Mackey]

Here is something that might help for all of you battery powering your devices:

http://derekmolloy.ie/changing-the-beaglebone-cpu-frequency/

I've effectively reduced power consumption to ~80 milliamps by slowing the cpu down to 300 MHz.

Naturally, you have to understand your situation.  I don't need high speed calculation or display - just moderate data crunching and large filesystem access. 

thanks, all, for the great feedback from my original question.

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[Fred Kerr]

Hello all,

I'm being just a little bit careful here:

I'm about to try this, but I will connect up the serial terminal first, so I can see output and interact with the board. (Graceful shutdown!)

I will test the serial connection first with just a micro USB charging cable rather than USB to a computer. (Simplify!)

It's my understanding that LiPo charging is disabled or not present in the firmware. (I'll give you the "uname -a" and other info the next time I fire it up. Just let me know what and how to check.)

Also, it's not clear (without reading the data sheet :) ) about the resistor values for the thermistor and the parallel (linearizing?) resistor.

If you have a 10K thermistor, do you put it in parallel with a 10K resistor, or likewise 100K thermistor in parallel with a 100K resistor? Do you put the thermistor anywhere in contact with the (e.g., 18650) LiPo?

From the prior thread, it seems to be sufficient (if even necessary) just to connect a 10K resistor from TS (P2-16) to ground (P2-15).

10uF cap from battery (P2-14) to ground (P2-15).

(Tangent/future: What about larger cap, perhaps using a 5.5V supercap, detect supercap discharging (lipo voltage to ~min input voltage on vbat) and give an interrupt to shut the board down?)

Thanks in advance for your help, and to the original thread authors!

Other posts that I found:

Safely power down the PocketBeagle supplied by a battery (no replies?):

https://groups.google.com/d/msg/beagleboard/dDSD89DGzpU/j2WzZyA2CgAJ

Supplying two ICs from the PocketBeagle powered by a Lipo battery

https://groups.google.com/d/msg/beagleboard/B7Zyf97hvzY/z8cOt0MHBwAJ

I want to do some excessive self-telemetry, both internal and external. I plan to scale the raw battery voltage by 1/11 with an op amp before feeding to one of the 1.8V ADC inputs. I'll defer to suggestions about measuring current.

(This is a tangent: I also plan to be paranoid if I connect to a car and want to monitor the car's "12V" with something like a VCO on the car side pulsing to an optoisolator, but I'm sure there are better ideas out there! :) (I could use several PIC -> nrf24l01 for some "really good" isolation!)

Thanks,

Fred Kerr

[Fred Kerr]

Maybe I need more than 10uf. It runs just long enough for only a few lines on the serial console.

[Fred Kerr]

1F 5.5v supercap helps.

I'll solder up the circuit with better current-carrying capacity.

Maybe I'll set up one of my other pocket beagles with scaled op-amp inputs with 4051 and op amp. :) Some day?

[Shannon Mackey]

"1F 5.5v supercap helps"

Curious, Fred, how long does it run on that supercap?  more than a "few lines on the serial console?"

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[Jason Kridner]

On Monday, August 27, 2018 at 11:15:36 PM UTC-4, Fred Kerr wrote:

Hello all,

I'm being just a little bit careful here:

I'm about to try this, but I will connect up the serial terminal first, so I can see output and interact with the board. (Graceful shutdown!)

Don't connect the power or RX (ie., serial cable to PocketBeagle) signals to avoid them interfering. Great thing to monitor.

 

I will test the serial connection first with just a micro USB charging cable rather than USB to a computer. (Simplify!)

Not sure what you are testing here. Are you just saying you'll power via the microUSB connection and not connect to a computer, just to see the behavior? You are monitoring with a serial connection?

 

It's my understanding that LiPo charging is disabled or not present in the firmware. (I'll give you the "uname -a" and other info the next time I fire it up. Just let me know what and how to check.)

It is not enabled by default. There is a flag in the PMIC that needs to be enabled. We've been playing with a driver to set the flag, but there are other bugs in that driver not related to actually charging.

 

Also, it's not clear (without reading the data sheet :) ) about the resistor values for the thermistor and the parallel (linearizing?) resistor.

If you have a 10K thermistor, do you put it in parallel with a 10K resistor, or likewise 100K thermistor in parallel with a 100K resistor? Do you put the thermistor anywhere in contact with the (e.g., 18650) LiPo?

Looking at the TPS65217 datasheet says to put a 75kohm resistor in parallel.

I'm not sure, but I believe the actual thermal resistor should be something like https://www.ametherm.com/blog/thermistors/thermistors-ntc-thermistor-temperature-sensors-provide-li-ion-battery-safety/. 

 

From the prior thread, it seems to be sufficient (if even necessary) just to connect a 10K resistor from TS (P2-16) to ground (P2-15).

Yes, that is supposed to work, ignoring the battery temperature.

 

10uF cap from battery (P2-14) to ground (P2-15).

(Tangent/future: What about larger cap, perhaps using a 5.5V supercap, detect supercap discharging (lipo voltage to ~min input voltage on vbat) and give an interrupt to shut the board down?)

Thanks in advance for your help, and to the original thread authors!

Other posts that I found:

Safely power down the PocketBeagle supplied by a battery (no replies?):

https://groups.google.com/d/msg/beagleboard/dDSD89DGzpU/j2WzZyA2CgAJ

I threw in a reply.

[Fred Kerr]

Yes, it ran quite a lot longer on the 1F, but still hung.

I wired this up (see pic) to be more stable than the breadboard mess I had. The led on 1.8k resistor is gonna run a lot longer than I'll take at lunch!!!

Can I isolate RX and TX or...oh I just need TX from the beagle for visibility!

1F 5.5v supercap (that battery was discharged to 3.96v). This one has more charge. Also put a 1000uf electrolytic on the soldered version, "because".

Fred Kerr (mobile)

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[Fred Kerr]

I'll try again soon with my more stable circuit (*soldered), also with RX disconnected so I just get output from the Pocket Beagle and the only power input is from the battery circuit. 

(*Soldered, so no loose breadboard connections, better current carrying capacity, etc.)

What is a good way to share log files? Mine can get verbose! I could store it somewhere and post a link - suggestions welcomed! I have a lot of possibilities, but just let me know what works best for you.

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[Fred Kerr]

It runs well with the soldered implementation. My breadboards are a little cheap.

The attached minicom_20180830b.cap shows a boot with microUSB power from a wall wart (from my rpi3), then a boot with the battery circuit. I left both RX and TX attached; I'll play with disconnecting them another time.

I'll look into getting some "telemetry" info from the pocket beagle. I'm open to suggestions about things to add/log, etc. Also, I think this pocket beagle doesn't have a fix that I got before - after the shutdown, things panic.

If anything else jumps out from the log file, please let me know!

[Fred Kerr]

I am looking for 10K NTC Thermistors with B=3480. How critical is the B value, or what range can I accept? Currently I am looking on Mouser.

Is there a specific or recommended battery pack? I'm just using an 18650 from a local surplus store.

Regarding the log file, I still need to do this:

sudo /opt/scripts/tools/developers/update_bootloader.sh

I'll also look for 100K thermistor with B=3960

[Graham Haddock]

Fred:

The temperature coefficient is only important if you are going to use them as temperature monitors, and you are going to thermally/mechanically attach them to the battery.

If you are just trying to get the battery power supply to run, and are not concerned about battery temperatures, a fixed resistor will work fine.

--- Graham

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[Fred Kerr]

I am concerned about the battery temperature for safety in my office, house, and around my 4-year-old son. :) And I'm curious about logging stuff infinitum.

I have it working with a fixed resistor (without attempting charging yet).

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[Jason Kridner]

On Thursday, September 6, 2018 at 10:22:38 AM UTC-4, Fred Kerr wrote:

I am concerned about the battery temperature for safety in my office, house, and around my 4-year-old son. :) And I'm curious about logging stuff infinitum.

I have it working with a fixed resistor (without attempting charging yet).

Did you ever get your thermistor working and enable charging?

 

On Thu, Sep 6, 2018 at 7:18 AM Graham Haddock wrote:

Fred:

The temperature coefficient is only important if you are going to use them as temperature monitors, and you are going to thermally/mechanically attach them to the battery.

If you are just trying to get the battery power supply to run, and are not concerned about battery temperatures, a fixed resistor will work fine.

--- Graham

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[Fred Kerr]

Hello, I had to put the charging project on hold but will pick it up again soon. I probably blocked excessively on finding an acceptable 10K NTC thermistor with the right B= value.

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[Taivas Gogoljuk]

I connected a 6v 5amp battery and it broke my bricked my pocket beagle.