APRS to monitor your Airstream?

[Scoutx]

Additional data plan option.

Freedompop

$5-10 for sim. $0 for a 200M per month data only plan.
overages either shutdown data or automatically adds data at $0.015 per Megabyte. User selectable.

A must read on this service:

https://www.cnet.com/google-amp/news...r-your-tablet/

[alano]

Sounds like a good deal, but it's not very useful in this project since SMS messages are required for communications. Anyone with an internet-connected tablet should investigate.

I've been testing the monitor now for about three weeks and there are some stability issues with MKR GSM library. As I'm waiting for the library to be stable, I'm going to rev the PCB one more time to change the connector layout. I should have something in a few weeks to share.

[alano]

Scoutx, after checking with the Freedompop site it does appear that they support 500 sms messages per month for free, so I ordered a SIM card. I'll need to change my software since it will no longer pass through an IoT provider, but heck, that's a simplification. I'll post an update once I get everything up and running.

[Scoutx]

May want to include what you've got of the IoT provider module as a seperate file just in case someone wants/needs that and/or if this service goes down. Would at least give someone a starting point.

Anyway it sounded like a cheap alternative option which is always good as that allows people more flexibility for their own needs.

Plus knowing of it opens up other options.

I'm thinking I may take the tracker and add a RTC chip driving the built in clock in the overhead which can then maintain accuracy and allow for daylight saving time changes. Should add very minimal power overhead. The clock and RTC would run on D cells and the GPS would provide accurate time for RTC updates.

[alano]

The code changes aren't extensive to switch from using an IoT vendor to 100% SMS, so I'll probably keep the code together and just use a compiler directive to enable or disable IoT.

When the GSM modem registers with the cell tower, the modem gets the time automatically. There's a choice of getting UTC time or the local time - taking care of daylight savings time updates.

Currently I'm using the cell tower location feature for GPS. I typically get about 1000 m accuracy. It's not great, but it's free. Perhaps a GPS module is warranted in a future version.

[Scoutx]

Well cell tower location does have the advantage of keeping hardware costs and power demands down. For theft prevention and such 1000m accuracy would probably be adequate.

Might include the GPS as an add-on option for those that might want closer monitoring, but that's minor.

But moving on...

I have battery analog clock in my overhead, what I was thinking since this will obtain accurate time, I could feed that to a RTC modual that in conjunction with a microprocessor would drive the analog clock movement. Normally the RTC would be driving the clock with the 1Hz output, but the microprocessor would handle time updates, and hand repositioning given a feedback loop that can locate the position of each hand once per cycle. I would set it up to run off a stand alone battery pack or 12 volt system. Haven't decided. I do know, I'm wanting to put a small solar panel on the roof to keep battery topped up and handle such parasitic loads. If so it might run off the 12 volt system, and shut down once voltage dips below 11.5 volts or if shut down by the tracker system. Which would allow remote control.

[alano]

Sounds slightly Rube Goldbergish but fun. You could possibly use an optical sensor to detect the back of the minute hand or even a tiny magnet and a hall-effect sensor. If you monitored both the hour and minute hand you could probably turn it off when you're not in the trailer and just watch it catch-up to the correct time when power is applied.

[Scoutx]

To some degree it is, but a self setting self regulating clock that is almost always right...would be nice to have. Plus since most of the hardware would already be resident and local to the clock the addition would be minimal.
Might even do something similar with my pair of wall clocks,. Though they would be more expensive to do since I would have to add the GPS or modem in order to obtain time data, and the processor might need to have a few more pins.

I can get a clock movement that triggers a output pulse each hour on the hour, which would be adequate to set minute and second, a hall effect on the hour hand would allow me to know twice a day the exact positioning of the hour hand at the time of the triggered pulse. That should place my hand positioning within 1-2 seconds. More than adequate. Particularly if I leave off the second hand. At which point you really only need to be within 10-15 seconds to be 'close enough' to be 'dead on'.

Oh, and I've tried the atomic clocks and find my ability to pick up the signal with any reasonable positioning of the clock to be nearly impossible. Hence the desire for something a bit more...robust.

[alano]

Originally Posted by Scoutx

Additional data plan option.

Freedompop

$5-10 for sim. $0 for a 200M per month data only plan.
overages either shutdown data or automatically adds data at $0.015 per Megabyte. User selectable.

A must read on this service:

https://www.cnet.com/google-amp/news...r-your-tablet/

Apparently, Freedompop won't work for Arduino and similar modems. The reason is that Freedompop's SMS messages are sent and received over GPRS using TCP/IP. So it looks like I'm stuck with Hologram's SIM. Their current rates are $1.5/month for the SIM card plus another $0.4/MB. One MB is good for about 1000 messages per month so it's more expensive than free but considering free doesn't work it's not a bad deal!

[alano]

Well I've finally got this project back on track after having to redesign it due to the loss of the Hologram dash module. It took some time to find a replacement module and even then I've spent many hours debugging the library support that was introduced with the module. In any event, I took the opportunity to make improvements. So here's the current features of the monitor:

• SMS-based interface – no apps needed
• Compatible with any phone, SMS-based commands and alerts
• Shore power detection
• Battery monitoring up to two systems, 12 V or 24 V
• Temperature monitoring
• Intrusion alarm with an input for a door sensor and an output for a siren
• General purpose input and output
• GPS location via cell tower triangulation
• Monthly history of battery voltage and temperature statistics
• Weekly status updates
• Over-the-air firmware updates
• SMS alerts for:

o Low or high programmable battery limits
o Low or high programmable temperature limits
o Shore power connection/disconnection
o Intrusion alarm with programmable siren duration

Here's a list of example screens:


Send *help or any text that the monitor doesn't understand will return a list of commands.


Advanced allows the user to configure the monitor. There is a general purpose input and output that can be enabled. You can configure a second battery system and configure a security alarm feature. A separate input and output is provided for a door sensor and alarm horn respectively.


You can query the cell connection.


You can perform poor man's GPS feature with cell tower triangulation.


You can see the cell voltage and temperature min/max for the last 30 days.


You can change the alert settings for cell voltage and temperature. The device will send one alert per day for each measurement that exceeds the corresponding setting.


You can ask for a status update at any time or the device can send you weekly status updates automatically.


You can request software updates!

Here's photo of the system, which includes a wall transformer for shore power detection and the temperature probe:


I'd be happy to support a few Airforum members to build their own system. I can provide a PCB but you'll need to be able to solder 0603 size components, purchase all other components, be able to install software via the Arduino IDE, setup your own account with Hologram, including purchasing a SIM card, and create a github account so you can access the project's documentation. In exchange for giving me feedback about the operation of the system you'll have your own system at cost. If you're interested send me a PM with your contact info.

What really drove me in doing this project was knowing whether or not my battery system is in good health when I pickup my trailer for an outing. Once I left the use/store switch in the use position for several weeks after putting my trailer away for storage and didn't realize it until I tried to pickup the trailer for a trip and discovered my batteries were dead. Luckily they weren't discharged for too long and I was able to recharge them with some difficulty. Losing your entire battery system isn't unrealistic. This shouldn't happen again with the monitor since the system will send me daily alerts should the battery voltage below a programmable limit!

[Scoutx]

Link

[Scoutx]

Here is an alternative to soldering. With care it allows you to mount small PCB components and make their electrical connections without the need for solder or heat.

Warning: do not use too much, pay attention to your working time and you can't make mistakes as this is an epoxy.

<Link>

[KelloggKid]

Al - I admire what you've done and would love to get on the band wagon. I sent you a PM yesterday but today I noticed a posting that said the PM system wasn't working. I checked my Sent folder and the PM to you was missing. I just tried the email method as an alternative. I'm a retired EE and ham radio operator with some limited experience with Arduino's. I have a MKR board coming and have also ordered a Hologram SIM.

Dale
W7HLO