Monday, August 30, 2010

DIY laser spirograph (part 3)

PIC based controller for laser spirograph.

The most advanced and sophisticated laser spirograph can be built only with programmable microcontroller.
Design of my spirograph is based on 8-bit microcontroller PIC18F1320 from Microchip.

PIC microcontroller implements software PWM generator with 3 independent outputs. Each output drives 2N7000 MOSFET (can be replaced with any suitable N-channel transistor with gate threshold voltage <5V). Fan is connected as load for MOSFET.
Device supports 5V and 12V fans with working current up to 200mA. Fan's voltage is selected by jumpers on board.
All  PWM outputs generate signal of the same frequency but duty cycle (0-100%) can be set individually for each output.

DIY laser spirograph (part 2)

Manual motor control.

The simplest and cheapest  way to control speed of DC motor is by using variable resistor connected in series with motor.
This method is applicable to any low power DC motor like 3V pager motor. Direction of rotation is selected by switch.
If you want to use chip cooling fans in your design, keep in mind that it's impossible to reverse cooling fan simply by switching power polarity since fan assembly incorporates electronic driver which is designed to maintain motor speed and direction of rotation.

Motor control. Simplest way.

Thursday, August 5, 2010

DIY laser spirograph (part 1)

Motorized mirror assembly.

Since laser spirograph is not intended to be precise optical instrument, any available reflective material may be used as a mirror.
I know some folks have experimented with regular glass round mirrors, dental mirrors, hard drive plates and built decent working devices.
CD/DVD media may be used as mirror too but because of data tracks CD acts like diffraction grate and splits bright laser beam into few weak beams.

DVD as a mirror. It may work as a temporary solution. 

Sunday, August 1, 2010

DIY laser spirograph (intro)

Simple laser show everyone can build.

DIY laser spirograph.  Cool and affordable laser show.

According to Wikipedia, spirograph is a geometric drawing toy that produces mathematical curves known as hypotrochoids  and epitrochoids.
Yes, it sounds like quite complicated scientific apparatus and, believe me, mathematical equations describing those curves look terrifying too, but it's a wonderful toy so if we leave boring science behind we'll learn that it's quite easy to build one and it's a real fun to play with.