For example, cars have a listener that knows when someone unlocks it with the remote key.. But how? The car is off, and the listener is always on..
That depends on how you set up your wiring, what components you want to use. etc etc.Like a arduino nano BLE that has a low energy state. this kind off set your BLE device in deep sleep. untill it got connected to a device.and still you have to calculate the drainage of the electrical system to calculate your battery's.
Because the 'listener' takes very little power and the battery in a car stores a great deal of energy in comparison to the the requirements of the 'listener', so the battery can power the 'listener' for weeks without significantly discharging the battery.
I figured so, do we know how much battery can last? Like is there calculations or something?
Is there any recommendation on which approach is the best? Wifi/blue/radio? Which takes the less power on sleep mode?
Depends on what you want to use it for? like are you going to be in a range of let's say 5 meters around the controller, i would recommend using BLE.But if you want to control it in let's say a another country i would use a wifi controller or a nano with a LTE Module.And if you are going to be in a radius between 10-1000m then 2,4ghz should do the trick. but that's only in open air.The point is that so far i know only the every BLE and every Wifi supports deep sleep state.
True, but if you make your app in mit2appinventor then that can all be done while building the app.But if you use wifi connection you are better off buying a esp8266-01 relais module and modify it.Download a simple sketch en connect it to blynk. download the blynk app and voila you have yourself an awesome smart bulb! like they called it 'smart'. it's just a simple on and off connection.
What i'm saying is based on whatever you are going to use, you still have to calculate your battery in amps.Otherwise the capicity won't be enought to power your project for the time you want it to.First of all it's best to learn the basics of calculating power and energy. and how it works. from that point on you can decide to use what you want.and what i'm saying about the app you can make a ble connect button in the app, after connected to the ble you can use the bttns in the app.
well, if you are going to use a esp8266-01 relay and a stand alone esp8266. you are able to use it stand alone! and it's cheap aswell! i used it in my house aswell.Works without a flaw.The thing is that you need an usb to tll usb. like USB to TTL serial converter CP2102 UART.This is needed for programming the esp8266. and take a good look at the wiring of the esp8266 to put it in programming mode! programming can be done in the arduino ide, this will overwrite the standard esp8266 AT Firmware.
what do you think about the NodeMcu?