Help with my 'roata random' mechanism - Is this the best approach?

DIYroboticsrandomizermechanics

Registration:
17.01.2023
Messages: 1198

GreenLantern Topic author

30.01.2025 19:31

I'm building a small automated display for a science project, and I need a reliable way to rotate and randomly select items. I've been looking into using a combination of servo motors and a mechanical randomizer, which I've tentatively labeled my 'roata random' system. My current design uses three separate motors, but the timing seems inconsistent, and I'm worried about mechanical wear. Has anyone successfully implemented a similar random selection mechanism? I'm open to suggestions regarding stepper motors or perhaps a simpler, purely gravity-fed system that achieves the same randomness without complex electronics.

20 Answers

15.05.2024
Posts: 359

SystemRoot

11.03.2025 02:36

Have you considered a tumbler system? They are much more reliable for true randomness than multiple motors trying to coordinate.

03.11.2021
Posts: 1309

Father_C

24.03.2025 01:15

Stepper motors are generally better than servos for precise, repeatable movement, especially if you need to count rotations. But for pure randomness, they might overcomplicate things.

29.08.2022
Posts: 113

Ghost_C

11.05.2025 16:52

If the goal is randomness, gravity is your friend. A simple inclined chute or a weighted pendulum system can achieve excellent results without complex electronics. Look into kinetic energy transfer.

04.10.2022
Posts: 620

Cousin_C

21.07.2025 15:44

What kind of items are you randomizing? The size and weight of the items heavily influence the mechanical solution. That's crucial information.

12.01.2023
Posts: 289

PipBoy

04.08.2025 19:16

I had a similar project. My biggest issue was friction points. Even a small misalignment can throw off the timing dramatically. Use bearings everywhere.

15.01.2023
Posts: 1135

Cait_F

05.08.2025 09:14

I think your 'roata random' concept is overly complex. A simple wheel with weighted sections that are dropped into a collection bin would be far easier to build and calibrate.

23.02.2022
Posts: 471

IceQueen in response

06.09.2025 08:03

Reply to the gravity suggestion: Could you elaborate on the angle of the chute? I worry that if the angle is too shallow, it will just slide in a predictable manner.

17.04.2024
Posts: 1070

Piper_W

11.09.2025 23:31

Have you looked into using an array of spinning drums? Each drum could hold a set of items, and you could use a single motor to spin them independently, then let gravity do the selection.

27.08.2023
Posts: 1379

FrostGiant

21.09.2025 01:21

I recommend a mechanical shaker combined with a funnel. It's simple, cheap, and the randomness comes from the initial kinetic energy, not precise motor timing.

16.07.2023
Posts: 1221

TechGuru

30.09.2025 02:48

Short answer: Yes, it's possible, but maybe not with three separate motors. Try synchronizing them with a single, powerful stepper motor and a timing belt system.

10.08.2023
Posts: 266

CSGO_Pro in response

03.01.2026 01:13

I agree with the tumbler idea. They are robust. You could even build a scaled-down version using 3D printed components for the internal baffles.

09.03.2023
Posts: 958

CyberWolf

29.01.2026 00:14

Be careful about mechanical wear. If the items are abrasive, you need hardened steel components. Otherwise, plastic parts will fail quickly.

04.04.2025
Posts: 1036

UnrealGod

31.01.2026 07:18

If you are worried about consistency, ditch the motors entirely. A weighted drop mechanism that hits a collection point is the most reliable way to guarantee true randomness.

28.12.2025
Posts: 87

Student_C

08.02.2026 16:07

The key is inertia. You need a mechanism that builds up enough random, unpredictable momentum before the selection point. Think less motor, more physics.

09.02.2023
Posts: 653

VoidQueen

26.02.2026 15:35

I've used a simple rotating drum system powered by a DC motor and a variable resistor. It gives good enough randomness for a science fair without needing complex microcontrollers.

03.08.2022
Posts: 752

Angel_C in response

28.02.2026 00:31

Reply to the stepper motor suggestion: If you use a stepper, make sure your motor driver is rated for the torque required when the system is fully loaded. Overheating is a real risk.

26.03.2024
Posts: 792

CryptoKing

01.03.2026 00:12

For a science project, simplicity often wins points. A purely mechanical, gravity-fed system demonstrates understanding of physics principles better than complex electronics.

01.10.2022
Posts: 1252

TitanStrike

14.03.2026 19:49

Have you modeled the system using CAD software? Running a basic stress test on the joints and pivot points could save you a lot of physical prototyping time.

04.08.2025
Posts: 843

LinkHero

20.03.2026 09:56

I found that using a slight vibration source (like a small eccentric motor) before the selection point greatly improved the mixing and randomness of the items.

17.02.2024
Posts: 264

Master_C

30.03.2026 03:05

I'd suggest looking into commercial 'selection wheel' mechanisms. They are designed specifically for this and often handle the complexity of timing and wear.

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