Party Like Music Produced from Acid Machine overview and explanation

Overview

This machine works by making a LED blink in the frequency of the sound and a set speed rotates the image.

Explanation

On top of the machine is the circle that contains lines where the notes being played are displayed while rotating. The lines in the middle circle will be standing still when C is played which will go outward and all notes will be displayed on a keyboard in 12 steps. The musical frequencies are displayed in centimeters for the distance between the lines. The frequencies in the circle are transformed by a script made in PHP to display the notes. To find notes using the potentiometers on the synth, the circle can also be used.

A simple noise generator and a filter comprise the sound part of the machine as it is based on logic ICs. A binary counter and a resistor ladder are used to make the 4-bit saw which is the sound the synth generates. The rotation speed of the tone wheels is determined by the red knob or the potentiometer on the controller. The notes are played as an arpeggiator by the sequencer which comes is 2 different modes.

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Automatic Night Light Feeds Directly From the AC Line

There are many approaches to the problem of activating a light when it becomes dark, and a recent Design Idea covers this topic (Reference 1). Some approaches require a dc power supply and an electromechanical relay, but a better approach involves feeding the device directly from the ac line, minimizing the number of components 

(Figure 1).

Figure 1. The photoresistor activates the TRIAC and the load when darkness falls.

The heart of the device is a light-sensitive cadmium-sulphide resistor, PR, with a resistance of approximately 200 kΩ in the dark and decreasing to a few kilohms in the light. PR and capacitor C1 form an ac-voltage divider. In daylight, the voltage across PR is too low to generate the required gate-trigger current to turn on bidirectional ac switch Q1, thus keeping the load – usually a lamp – off. When it becomes dark, PR’s resistance rises, resulting in an increase in the TRIAC’s gate current that triggers the TRIAC and lights the lamp.

The schema uses inexpensive, off-the-shelf components, including the VT90N1 photoresistor; a 0.1-μF, 275V capacitor; and an L2004F61 TRIAC with a load current of 4A rms, a peak blocking voltage of 200V, and a gate-trigger current of 5 mA. The exact specifications of these components are not critical; you could use others instead.

Editor’s note:
Attributes worth mentioning include the fact that the capacitor introduces a phase shift, which places the peak of the gate voltage close to the zero crossing of the load’s sine wave for optimum turn-on timing. Another benefit is thermal hysteresis, which occurs due to the reduction of the required triggering voltage and current as the TRIAC warms up after the initial turn-on. 

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