I am pretty new with this stuff, so please bare with me.
My goal is to make a compact board to work as a stand alone battery powered unit to send alarms to my cell phone. These will be working in an environment without WIFI or bluetooth, so it will require a SIM-card. Also since this unit will be working alone for long periods and occasionally in cold -20...-30°C weather, the power consumption will be a big issue. Since I am planning to have multiple of these working simultaneously in my personal use, I would like to cut down the communication costs and device costs to a minimum.
So following requirements I have set for the unit:
Low power consumption, battery should last min. 2 weeks. I was planning 18650 Li-ion 3500 mAh battery for power.
1 x one on/off input, usable with magnetic switch, also used for wake up from sleep.
low voltage alarm
possibly gps built in
every day check for operation readiness
So basically what I imagine to need are following:
ATmega328 controller + essentials, UNO will do the trick in prototyping phase
Sim board
real time clock
possibly gps board
I have started with prototyping with Arduino UNO and SIM900 board, and I have managed to get sms through with push button. So a lot to do, and I would appreciate advice's for good tutorials regarding programming of these...
I was wondering, that how I handle the every day check of operation. One thing that I had in mind was to make every day a one dial tone call without answering, which would not eat any capacity of future PRE-PAID operator card, but I don't have experience, that how much energy that will consume...? Now I am mostly thinking of handling the communication with SMS (Switch information and low voltage), which aren't used very often I hope, and will not significantly use the sim card capacity. Sending a text every day of the operational readiness will consume the card pretty fast. One option of course would be a gprs via server, but I have very little experience on programming costs of that.
Idea of the gps was to send location in the same SMS as the switch information or low voltage information. And also send it with SMS request.
I have this in very early stages, but do you guys who have more experience with these, have an recommendations of the needed hardware also? For example would an ESP-32 be more suitable or etc...
Maybe in some point I could order a custom PCB Assembly including these components, but I think I am pretty far away from it now...
Do you need a SIM in each unit or are they close enough to each other to local network with Lora and have one unit be the master SIM.
What sort of distance are you looking at for the cell link? kms, 10kms, 100km, roaming?
You will need to research the temperature performance of all your hardware if -30C is going to be experienced.
Especially the batteries.
Can you allow a PV panel to supplement your power requirements.
If your only input is a switch, then making your hardware sleep and wake on interrupt would be advantageous to power consumption.
I have not had much experience with low power/sleep modes, but there are others here who can give you better info.
Do you need a SIM in each unit or are they close enough to each other to local network with Lora and have one unit be the master SIM.
What sort of distance are you looking at for the cell link? kms, 10kms, 100km, roaming?
You will need to research the temperature performance of all your hardware if -30C is going to be experienced.
Especially the batteries.
Can you allow a PV panel to supplement your power requirements.
If your only input is a switch, then making your hardware sleep and wake on interrupt would be advantageous to power consumption.
I have not had much experience with low power/sleep modes, but there are others here who can give you better info.
Tom....
Hi Tom,
Thanks for the prompt reply. -unfortunately the devices will be several kms away from each other and the operating radius from my location is 50 - 100 kms. PV panel is not an option, since I will need to move these around quite much. Just have to trial and error the battery capacity, but I believe sleep mode is essential.
Riva:
It might be worth looking at Kevin Darrah's trigboard. The video explains the details and also links to his tindie store.
Hi Riva, thanks for reply, I have been looking at Kevin Darrah's trig board, and it seems like a ready solution, but the down side is that it is purely WIFI / Bluetooth depending... Although connecting this with sim board, shouldn't be impossible...
-Tuomas
In order to save energy I suggest dropping the GPS. In stead You use a few controller inputs that can be binary coded by straps. Then You will know if the message comes from unit 0, unit 1, unit 2 etc. 3 pins, 8 units, 4 pins 16 units....
