Inside a cheap but impressive laser cube

These things are very widely available, which is a slight issue, as in the wrong hands they can pose a risk of permanent eye damage. This device should not be aimed at people's eyes and should NEVER be given to a kid as a toy.

The circuitry is notable for the way the microcontroller is powered via its own regulator, and then turns on the rest of the circuitry by enabling another adjustable regulator set to 3.1V.
That has two advantages. It greatly reduces standby current by disabling most of the circuitry in standby, and also allows the voltage to be chosen to suit the lasers with simple current regulation using a resistor.

The rotating diffraction pattern disk runs far too fast in this unit, but that could maybe be slowed with the addition of a series resistor to the motor, noting that too high a value may cause the motor to fail to start rotating.

I'm not sure if the voltage drop across the MOSFETs was due to PWM for laser current control or if they were not turning on fully and operating in their linear region.

The green laser in this unit appears top be a DPSS module (Diode Pumped Solid State) that uses an infrared LED to stimulate a crystal to lase at a different infrared wavelength, and then that infrared laser passes through another crystal that frequency doubles it to visible green light. Unfortunately that means that a lot of invisible infrared laser energy comes out, and very few companies make any effort to filter that out.
This is made especially dangerous by the critical nature of the frequency doubling crystal, which can be affected by temperature and other factors. It means that in situations like a cold environment it can look like the laser is very dim or barely glowing, and masks the fact that the full strength infrared laser component may still be present.

Here's a link to the item on AliExpress (not a sponsor).
This is an affiliate link, but that will not affect the price you pay.
https://s.click.aliexpress.com/e/_c2uNstuL
The item may not appear in some countries due to them proactively blocking lasers for safety reasons.
The price also varies widely between sellers. Aim for less than £10.
Suitable search keywords are:-
Rechargeable Battery R&G Laser Projector Disco




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