Battery life calculation using Nano, NRF24L01+ and window magnetic reed switch

Question

I'm trying to make my own home wireless security system. I will be using probably 3 AA batteries to power these devices. My problem is that I need to know if the batteries will be enough to power the devices for at least 6 months. Below are the details of all the devices I will be using:

1. Mini Nano V3.0 ATmega328P Microcontroller Board w/USB Cable For Arduino
2. Makerfire Arduino NRF24L01+ 2.4GHz Wireless RF Transceiver Module
3. uxcell MC 38 Mount Wired Door Window Sensor Magnetic Reed Switch Recessed

Below are some project requirements that might be useful:

1. For the Nano, I want to put it to sleep using delay(2000) in the loop() function. The Nano will be the one checking the window sensor.
2. I will be using a project enclosure of about 4X4 inches.

If this will not be possible maybe someone knows of other devices that use less power that will be more suitable for this project? I would prefer something easy to use like Arduino Nano with USB so I can easily program it.

Answer 1

The components you've selected are inappropriate (assuming you selected items from Amazon): https://www.amazon.com/ATmega328P-Microcontroller-Board-Cable-Arduino/dp/B00NLAMS9C
and...
https://www.amazon.com/Makerfire-Arduino-NRF24L01-Wireless-Transceiver/dp/B00O9O868G?th=1

The Nano has extra components (LEDs, regulator and Serial/USB chip) on it that are not required. These will require power even when you put the MCU to sleep.

The NRF24L01 is ok, but won't run on 3 x 1.5 V batteries. This unit has no onboard regulator (which is correct for your application) but would only be suitable for 2 x 1.5 V cells

Answer 2

I would suggest you simply get a switch that only closes when in the tripped position. Then it can power up your system, if the switch does not have the current capacity a MOSFET will do the job. This will give you zero standby current extending the life of your batteries. If it is going to remain triped for a long period of time you can have the arduino shut down the power. You can find a lot of circuits on the internet that do this. For power use the three batteries in series and tap at the second point for the NRF24L01. It is possible to do what you want without the Nano, I have come across it on the web where they use the NRF24L01, a switch and minimal circurity. However I do not remember many of the details.

I was thinking about this and came across this: https://www.youtube.com/watch?v=RrmpN1_Py_4 it does the design going through the battery calculations etc. Give it a try, there are several parts to it.