Trying to help grand-daughter

Trying to help granddaughter

   Hello Folks

I hope I’m posting this in the right place, forgive me if not.

I am studying Arduino and bought the Elegoo Super Starter Kit to help me along the way.
I have a granddaughter with high-end autism, they used to call it Asperger's. It makes her very anxious, and she’s having trouble in high school as part of it.
May I ask for a little advice from you kind people?
I would like to build a “Useless Box” to try to distract her over active mind sometimes.
I have been studying the many boxes on here and YouTube and I think I know what I want.
What I would like to do is put a vibrating motor in the head of the doll and have it shake vigorously “in frustration” at a point or two in the cycle.
I’m pretty sure I can do it with an ATtiny85 type board, I only need 3 pins really. Two PWM for the servos and one digital for the vib motor. I know to run the servos and motor off a 9V battery. I have started to read some info on just using the chip by itself to run this thing. Once it’s programmed, that will be it. Your thoughts?
Now, if you don’t mind, some more questions.
Unlike so many posters on the forum, I want my motor to shake. I’ve seen many motors on Alibaba and such that might work. Any of you use a counter- weight vibrating motor? Which one would you recommend?
Can I simply cycle it on and off again with a simple switch command without the use of a shield to control the motor? I don’t need, or want really, speed control.
Is it the usual case for the board to power up from the USB, when it is available, and switch to the 9V when it’s not? The idea is to make the box portable.

Thank you for your time

What servos? Normal hobby servos are powered by 4.8V to 6V. 9V will probably damage them.

Servos do not need PWM pins. The servo signal is PWM but not analogWrite type PWM. Any digital pin will control a servo. Use the Servo library.

9V smoke alarm batteries do not have very much current capability so will not last long powering an Arduino and even a small motor.

Arduino output pins can only supply a recommended max of 20mA, probably not enough for a motor. Use a logic level MOSFET to drive the motor. Make sure that the MOSFET will handle the stall current of the motor.

You could use a 4AA (or AAA) cell battery pack to power the servos and motor. That will provide ≈6V. Put a silicon rectifier diode in series with the battery pack to the Arduino 5V. The diode will drop the 6V to 5.3V to 5.4V to supply the Arduino (max supply to most Arduino processors is 5.5V). Feed the servos the full 6V.

I’m a little confused…
What. does a doll have to do with a ‘useless box’ ?

Second point. If you’re thinking of a PP3 style battery, they’re no use for driving motors of any type.
It would barely keep the processor alive for very long after the losses through the onboard regulator.

I’m sure we can help…
Maybe a pencil sketch or links to something similar.

Good luck.

Thank you
It's a useless box in that when you turn on the switch on the outside of the box, it turns itself off again. They can be very simple and only go through the cycle once, or they can have several cycles programmed in, doing different actions. They can also be made with more than one switch.
If you look up useless box on YouTube, you'll see how it works. When the switch on the box is turned on, the lid opens and the doll head pops up. Then a hand comes out to turn off the switch. It then returns to the inside of the box and, depending on the programming, a new and different cycle will operate when the switch is turned on again.

A 9 volt battery is what I used to use in my R/C airplanes, worked just fine.
I don't yet know how to attach a pic of the circuit diagram but this URL, DIY Useless Box with Arduino - YouTube is something like what I want, and it has a link for the circuit at Angle Fire.

This is something like what I want.

Figured out how to upload a pic.
The servos need the PWM to be able to set their position in the box, do they not?

Ok, a standard ‘useless box’.
The doll element had me confused!
If you’re happy with the PP3 battery, that’s fine, most if the old-timers here would suggest a bundle of 4x AA cells in a holder for more current at the right voltage.

I’m guessing from your drawing, the doll is simply on a spring or is otherwise independent of the box, latches and servos. That’s a mechanical issue.

It’s probably not worth going much further here, because there are countless tutorials and build videos for these - both single and multi switch versions are out there in the tens.

What we can do is steer & help you through the challenges you may encounter, or to enhance the code when you’re on the way, and you have it basically working.


Lastchancename, thank you

If the PP3 doesn't work out, it's easy enough to change.
The doll head is, indeed, not connected to the workings, it is glued to the lid, so it appears to pop up.
So, is my initial post info and questions OK?

Don't see the motor on that diagram. :face_with_raised_eyebrow:

Remember that you need a transistor - preferably a logic-level FET - to switch the motor, it cannot be directly connected to the Arduino.

Buy a bullet vibrator.

Cut the cord, put the vibe into the head, use the power wires to control the motor on/off time.

Next, use one of the smaller Arduino boards.

The event happens, a small relay is energized, the motor rotates and vibes, the time runs out the relay is deenergized, the motor stops.

Better yet, drive the motor with a MOSFET and use PWM to get differing rates of vibe.

You may find it advantageous to develop your system on a regular Arduino board UNO or Pro mini or Nano whatever where you have plenty of pins and serial i/o easier.

Then when indeed you are really only using three pins and have no need for any serial monitor stuff finding errors you can move the code onto the ATtiny85. With any planning this should be reasonably straight ahead.

i have many projects running in the UNO which woukd be fine on an ATtiny if I ever carried through with the original plan. :expressionless:


Thank you
Good advice, saves a lot of headaches.

Electric Be-Wa Balls!
That might just work.
Got a link HeHeHe

That is the advice direction I needed, thank you.
I knew I couldn't power off the Arduino, so now I can look up logic-level FET.
The motor is something I want to add to the sketch, and so your advice fits right in.
Thank you

I just read up on MOSFET's.
That is just what I need, I think, it acts just like a relay for my old car's headlights.
I put aircraft landing lights on a car I had. Daylight at midnight.

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