Electronic – Recommend motor type to turn baby rocker, into auto-rocker

dc motormotorstepper motor

Would like to convert a baby bouncer (like this one), which requires continuous manual effort to rock it, into one that use electro-mechanical means to auto-bounce. However, my aim is to make these on the cheap (as all of my other projects so far have). So I am on the look out for alternative design approaches or parts.

My idea is to place a low RPM, high torque (unable to quantify, since I've not work with DC motors, beyond the ones found in small toy cars etc.), DC motor (brushless?), which periodically winds (like a winch) pulling the bouncer seat to the low-position, and then (here is where, I am not sure, it is right or feasible to do with standard DC brushless motor), just de-energise the motor, for the bouncer to bounce up, and have few naturally dampened oscillations (bounces), and then repeat the process.

Is the above approach correct ? Will de-energising the motor, and the rapid unwinding in opposite direction, make it act like a dynamo and feed current back into the circuit ? Can that harm the motor ? Will stepper motor be a better approach ?

Best Answer

How about an alternative approach? Use a solenoid.

Solenoid baby rocker

You only need to inject a little bit of energy into the system to get it oscillating. Wind up a big coil. Attach a steel rod to the back of the rocker, and when you energise the coil, it will pull the rod into it. Switch the current on and off, and you'll cause the rocker to bounce up and down. If you time it correctly, you'll achieve resonance. The best way to do this is to have a little sensor to detect the position of the steel rod. Energise the coil when the rod is all the way out of the coil, and de-energise it when it's all the way in. This has the advantage that it'll be quiet.