Hi,
I have a smal battery operated led sign that i was thinking about turning "smart".
My first thought was an esp but quickly realized that it would probably only be operational for a day (max) then my 3 AAA batteries would have to be switched..
I also thought about a RF433 receiver but couldn't figure out how to get it low powered. I have tried searching the web but haven't found much.. So now I am looking for a low powered microController of some kind kapabel of receiving commands wirelessly over wifi, RF433 or any other greate alternatives. All it is going to do when it receives the right command is to turn on the light with a relay or a pnp Transistor or simular.
I would love some alternatives or different ways to solving my problem.
Hi
All microcontrollers will have some sort of sleep mode. Battery driven electronics with microcontrollers usually sees the microcontroller itself asleep for the vast majority of time. It's fairly easy to have an ATMEL 328P (as used in the UNO) to keep running for a year or more on a few AA batteries by just having it only on once a minute, for example sending a sensor measurement.
If you want a device that listens, rather than sending a signal, it's a bit tougher on battery power as the receiver needs to be constantly powered up. It may not use much power, but if on 24/7 that soon drains the batteries. Typically devices that use for example 433MHz the battery operated side is the sender, with the transmitter turned off between sends and in reality only on each minute for a few milliseconds. The receiver is typically mains powered and so can remain on listening.
An interesting work around to a receiver being used in battery operated devices is used in things like weather stations, where the base station runs on battery power and needs to listen constantly for the senor readings. The receiver is only turned on when the signal is expected, so in learning mode the base station listens constantly for a few minutes, each sensor reading is received, then it knows from that point the next reading arrives in x seconds. So it turns on the receiver just before the sensor transmits, then turns the receiver off again until the next sensor reading is due. Is this something you can do if you don't need an immediate response?
Low power over Wi-Fi for battery operated devices (where battery run-times of months are required or expected) is very hard to achieve. Wi-Fi was never designed for this sort of use case, which is why we have ZigBee, low powered Bluetooth or products using medical bands and their own simple protocols.
My advice would be to look at the something like the nRF24L01+, if you search on Ebay these can be had for very little money and experiment with these, or at least searching for that term you will find loads of examples of this in use with battery equipment. Although the issue of long battery life when the device is the receiver and on constantly is still a problem. Perhaps turning the receiver on once every 10 seconds, off for ten seconds might be responsive enough for your application. This would mean your transmit signal would need to be repeated for at least 11 seconds each time for the receiver to get a chance to hear it.
Lee