Hey guys, sorry if I keep on asking a lot of questions.
I am planning to run an SX1276 module and a soil moisture sensor to an Arduino Pro Mini (3.3V, 8 MHz) via a 12V, 12.8 aH 3s2p battery pack. The battery is shown below for the reference.
Is it okay to plug the 12V supply to the RAW input of the board, considering the amount of pins to be taken by both the module and sensor? If not, what will be the proper workaround for this?
Thank you.
Do you plan on connecting anything to the Pro mini Vcc pin?
Just the single Vcc coming from the module and the sensor. The two of them are connected onto a breadboard, and a spare connector from the breadboard to the Vcc of the Pro Mini.
The problem is, if you use the 12V battery connected to raw, then you cannot draw a lot of current from the Vcc output. I think the SX1276 module will draw too much current.
Can you post a datasheet fot the SX1276 and soil moisture module?
Hi Jim.
Attached below are the datasheets of the SX1276 and the soil moisture sensor.
SX1276: https://www.mouser.com/datasheet/2/761/sx1276-1278113.pdf
Soil Moisture Sensor: Soil Moisture Sensor Module Pinout, Features, Specs & Circuit
Depends on the useage pattern.
The LoRa module can consume in the region of 100mA (or more) and the rest of it maybe 20mA depending on how you are using it. In that case the tiny regulator on the Pro Mini will need to dissiapate (12.6V - 3.3V) * 0.12A = 1.16Watts. The regulator would fry.
Using a 12V battery is a big risk.
How you safely power the setup does rather depend on the application.
Will using a buck converter suffice? Like a LM2596?
You can connect the soil moisture sensor to the Vcc pin but not the SX1276, it uses to much current. You will need a 12 to 3.3V buck converter. So you might as well power everything from the 3.3V buck converter.
I don't recommend using an adjustable buck.
Find one that goes from 12v to fixed 3V. 1A current rating is plenty
This is noted. Thanks so much.
Like this
Would stepping down to 7V be a good idea? I've read that the minimum input voltage around the RAW input of the Pro Mini is 7V.
I assume you are planning to use LoRaWAN to the TTN server
I would recommend that you get the SX1276 working with the Pro Mini running from USB and connecting to the TTN server
once it uplinks/downlink then worry about powering it from baattery
If your using a step down converter, then it makes sense to step down to 3.3V, no potential regulator overheating issues then.
Would stepping down to 7V be a good idea?
You can power the pro mini with 3.3V connected to the Vcc pin but make sure you have nothing connected to the raw pin
Yep, I did manage to get the uplink/downlink from the TTN server via USB-UART.
Once I have stepped down from 12V to 3.3V, then can I safely connect the stepped-down 3.3V to the Vcc pin? Assuming that I should make sure that RAW pin has nothing connected to it.
See post #15
This is noted. Thanks so much, Jim.
This is noted. Thanks so much.