Baby cradle rocker

Hi, I want to create a rocker for my coming baby's cradle.
I've been spent the whole day googling but I cannot find basic details about the setup.
It's worth knowing that I have never done anything with Arduino before, so this would be my first project.
Ideally, I'd like this to have microphone activation (when the baby cries) but for now, I'll already be happy having just a motor that rocks the cradle.

I understand that I need:

  • Arduino Uno
  • Servomotor
  • Rope to connect cradle to servomotor
  • Microphone (later)

I'm looking on AliExpress for a servomotor but I genuinely have no idea which one to buy.
Which one would you recommend?

Thanks in advance, your help is highly appreciated!

Why use an Arduino? Use a geard motor and a crank shaft.

Honestly, this does not sound to me like a safe idea. It's not that there are so many things that can go wrong, but that the cost of failure is so high. :frowning:

Honestly, this does not sound to me like a safe idea. It's not that there are so many things that can go wrong, but that the cost of failure is so high. :frowning:

do you mind elaborating on that?

do you mind elaborating on that?

Sure. Dead baby.

Or crushed fingers at least. Baby progress comes without warnings. Enjoy the feeling of doint the rocking manually.
On baby was put in a swing. The swing was made swing until the "passenger" turned into a sack of potatoes.
The next baby was put in the baby bed, laying on the stomach, and my firm hand was doing the rocking, laying on the floor, impossible to "buy", to abbondend the go asleep program.
Using a "machine'".... You will miss fine memories.

There are commercial versions of this.

Primarily, and in regard to the safety aspects, the cradle has to be designed for rocking; the mechanical aspects are far more significant than for whatever an Arduino might be needed, which is debatable.

And you would need something a lot more substanial than the typical “hobby” servo. :astonished:

Are you thinking about a curved wood base on the floor ?
or the hanging bassinet ?
or a perambulator that has a spring suspension ?

A simple motor with a cam can be secured to a wooden base and push on the floor. A small movement will have the effect of motion to the occupant.

I am guessing that the little one will not be climbing out of the safety cage any time soon so like every door in the house, every drawer and cabinet that has a pinch-point, the base to floor will not have fingers any time soon.
An extremely simple finger guard can be installed faster than reading this thread. So, on the safety side, the there is no issue.

The string to a wall is another way.

The basic concept is speed. Watch a baby rocking and count the times per minute movement
That is your desired motor RPM.
The distance of movement is the distance from the axis if the motor where the string is attached.
Lots and lots of 12v motors with 50-60 RPM or even much less.

You should be able to find the hanging kind of baby swing, often with a motor that swings it and plays a lullaby if you want.

You could add a movement sensor to know when the little one is active and send you an alert, or start a gentile swinging.

The piston on the floor allows for a very soft and gentle movement but can also be set to be more aggressive.
The need for the aggressive action is to mimic a car on a road which mimics the ride jr. was on for the last 9 months of being jostled, and jolted, pushed and squished. A low speed vibrator is not hard to make, but adds more comfort for the little one to help them fall asleep.

first step
take a string, take your rocker, get a cup and some water
tie the string to the rocker, put it over a door knob and connect the cup.
add water.
lift the cup and let 'fall'
empty and it should not move the rocker
add water until it does
lift it, let it fall
the least amount of water needed is the goal. weigh the cup.

trigonometry will tell you the distance from the center of the motor shaft to the radius point of the string attachment.
with that, you calculate the torque needed based on the weight of the cup.
that is your motor selection.

For a floor attachment, you need to move the rocker and measure the distance. Same formula applied when determining force.

Please, abandon this idea as your first project. You should at least prove your ability to build a robust and safe project before involving a tiny helpless human being.