Tale of two Dashes


#1

This may explain some of my recent posts about connectivity/deep sleep. I brought my original Dash home and been doing tests between the two devices (using same antenna and code). They both fire up, connect to modem, and send a Hologram message fine. But the newer Dash never shows up again after a deep sleep, while the old one does just fine. Both log the same signal strength when they start up. On the newer one if I don’t power down the modem, but go into deep sleep, it works. But the combo of modem power off and deep sleep appears to stop it from getting a connection after it wakes up.

Any ideas on trying to figure out what is wrong? I’d been programming with SMS handling using the newer one and it was so inconsistent, but I’d been blaming weak cell signal at home. After this test I’m not so sure.


#2

what is your signal strength at home?


#3

During the tests it was from 10-12%. The old dash would connect after deep sleep in 10-11 seconds (max time the code waits for connected status is 15s), then it would proceed to try and sendMessage anyways, which looks like it will wait another 10-20s for connection.

This morning the signal is 7% … and the new Dash is working. Well, it worked once I cranked up the max wait time. It appears that this board takes an extra five seconds or more to establish a connection.

I know, I know “why not have a much bigger wait time?” Since this is sipping a battery deep in the woods I’ve been trying to minimize how much battery is being used when it wakes up. If there’s a problem with the cell signal I don’t want it to wait around wasting battery. I’m fine with missing a reading from time to time and the old Dash usually connects from 6-12s after powering up the modem and so I’ve been optimizing for that.

I have this idea that maybe after powering up the modem, it can go into deep sleep for 10s while the modem is establishing connection with the tower. Then wake up and spin for a bit checking for connection.


#4

I’m also in the range of 8-12 signal strength and it’s tricky to get consistent connections. moving the board few inches and connection break. It start working great with 15 signal str. It also gives me headache to test with low signal. Do you monitor the behavior with leds or serial monitor? When I compare my dash with GF cellphone working on the same carrier, her cellphone connects more easily than my Dash V1.2.


#5

I’ve added signal to the data coming from (old) dash in the woods. Surprised to see it hovers around 8-9% and yet always connects.

And by “old” they are probably a month or two apart.


#6

I am currently doing a battery life test and for about 5 days, I have no network where I had a signal of 20. I start to doubt like you that there is to be a problem somewhere. Milivolt reading is also bad 4200 and few reset after, 2900, multimeter says 3.75v


#7

I’ve been able to get 30 days out of one 2700mAh 3.7v battery so far and that’s when we had a lot of sub-freezing temperatures. This is waking up every 15mins to send sensor data. My new code swaps over to 30 mins after 8pm - 6am, since we don’t really need as up to date temps then (mt biking trails). Not sure how much longer the battery would last with that, it was up to 15 days and still around 3.8v, but I did an OTA update with the deepSleepMin(7) after powering up the modem and after it booted up and sent initial message I never heard from it again! ":^)


#8

Just a “heads-up”. Check the manufacturer’s datasheet for the charging temperature range for your cells.


#9

Good point. Originally I thought I could just bring a USB battery pack out, hook it up and go biking while it tops off the battery. The guy who 3d printed the case suggested just swapping out batteries instead. It’s in the woods and would be tough to get enough light for a solar panel trickle charge anyways.

I have another project where the Dash would be on a trail kiosk driving an e-paper display. It’s a good candidate for a solar cell. But what to do in the Winter when we get below 0˚F temps for a week? I’m not sure if the e-paper displays will function in that temp. Maybe wait for it to warm up enough and sneak in a quick charge & screen update. ":^)


#10

But what to do in the Winter when we get below 0˚F temps for a week?

It doesn’t get that cold here even over-night! I am off-grid using LiFePO4. The recommended charging temperature range is 5C to 45C (battery guru advise). As the batteries are outside I have them in an insulated box with a 25Watt/Hour heater to keep them at 20C. It can be on all night.

A heater is probably not a option for you. Also my manufacturer said min charge temp -45C, so I suggest you find out general user recommendations.

Solar panels generate quite a bit of heat, maybe you can channel that into the batteries and start charging when they get up to acceptable temperature.


#11

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