Power consumption for small servo project

Projects General Guidance
1

Hi everyone,

I am planning to build a small micro servo project to switch my bedroom light on and off. This is the only way I can do it (with a servo) because I don't have permission to modify any existing electrical stuff with the light switch.

I am planning on using just the ATMEGA328p-pu on a small breadboard with a micro-servo attached, and also a RTC module (DS3231) for scheduled On/Off switching.

If I power the the ATMEGA328p-pu, the micro servo and the RTC module with a 9V battery, how long would it last if I switch the light on once a day and off once a day?

I am also very new to Arduino, so I am confused as to how "sleep mode" can be enabled but still keep an eye on the time from the RTC so it can trigger the servo, any guidance and help would be greatly appreciated.

Thanks!

2

If you mean a PP3 style 9v battery the answer is not very long.

If you are just using an Atmega 328 why not use 3xAA cells - that way you won't need any voltage regulator. An Atmega 328 will happily run at 8MHz on 2xAA cells but the servo would probably need a higher voltage.

I think you will need something to disconnect power from the servo or it will consume all the battery power on its own. This assumes, of course, that the servo will hold its position without power.

...R

3

The total power consumption mainly depends on the servo power, and the servo power depends on its torque, and the required torque depends on how much force is required to press the original light switch.

So how does your switch look like, and how much force (gram, pound) is required to press it?

4

Another point to consider is how you intend to manually operate the switch if required.

5

@Robin2 I hadn't considered using 4.5 volts, I also didn't know that servos are power hungry, I will need to figure out a way to cut power to the servo as you suggested.

@DrDiettrich My switch looks like a circuit breaker switch, not really a normal lightswitch. I am honestly not sure about how much force is required to press, I don't know how to go about getting a ballpark figure for that. It makes a lot of sense about the power required after having read your answer! Thanks

@bluejets I am going to use a design by the folks at Oomlaut that allows manual operation, it also uses a micro-servo to flick a switch on and off. You can see the design here: http://www.instructables.com/id/Easy-Home-Automation-using-servo-switches/