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 == On Thu, Sep 6, 2018 at 3:34 AM Fred Kerr <[email protected]> wrote: > 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 > > On Thursday, August 30, 2018 at 5:35:43 PM UTC-7, Fred Kerr wrote: >> >> 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! >> >> On Wednesday, August 29, 2018 at 10:59:03 AM UTC-7, Fred Kerr wrote: >>> >>> 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. >>> >>> On Tuesday, August 28, 2018 at 12:51:23 PM UTC-7, Fred Kerr wrote: >>>> >>>> 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) >>>> >>>> On Tue, Aug 28, 2018, 12:13 PM Jason Kridner <[email protected]> >>>> wrote: >>>> >>>>> >>>>> >>>>> 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. >>>>> >>>>> >>>>>> >>>>>> >>>>>> 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 >>>>>> >>>>>> On Friday, November 10, 2017 at 10:32:46 AM UTC-8, Adam Saenz wrote: >>>>>>> >>>>>>> Keep in mind that the 7V is Absolute Max voltage so you should >>>>>>> operate below this level or risk damaging the chip. >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Thursday, November 9, 2017 at 10:15:05 PM UTC-8, Shannon Mackey >>>>>>> wrote: >>>>>>>> >>>>>>>> >>>>>>>> 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! >>>>>>>> >>>>>>>> -- >>>>> For more options, visit http://beagleboard.org/discuss >>>>> --- >>>>> You received this message because you are subscribed to a topic in the >>>>> Google Groups "BeagleBoard" group. >>>>> To unsubscribe from this topic, visit >>>>> https://groups.google.com/d/topic/beagleboard/PQCNhmeBK3M/unsubscribe. >>>>> To unsubscribe from this group and all its topics, send an email to >>>>> [email protected]. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/d/msgid/beagleboard/846799d8-d0bf-481a-9599-cd3b97c1b065%40googlegroups.com >>>>> <https://groups.google.com/d/msgid/beagleboard/846799d8-d0bf-481a-9599-cd3b97c1b065%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>> . >>>>> For more options, visit https://groups.google.com/d/optout. >>>>> >>>> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/84b1f839-cfe2-4dff-b9b3-ecffdc9f2527%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/84b1f839-cfe2-4dff-b9b3-ecffdc9f2527%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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