Production of two-color music lantern

The device can make the green and red colored light groups flash continuously with the change of the height and strength of the music frequency, producing the effect of sound, color and light being integrated into one, giving people a beautiful feeling.

How it works

The two-color music lantern circuit is shown in the figure above.

This circuit first divides the music electrical signal from the speaker into two frequency bands, high and low, and then controls the on and off of the two bidirectional thyristors VS1 and VS2 respectively to achieve the purpose of controlling the corresponding green and red colored lights to flash.

The music signal from the speaker passes through the terminals X1 and X2, the voltage divider potentiometer RP (for sensitivity adjustment) and the isolation and step-up transformer T, and is divided into high and low frequency bands by the frequency dividing elements - capacitor C and inductor L, and is added to the control ends of the bidirectional thyristors VS1 and VS2 respectively, as a trigger signal to control their conduction angle, and then control the voltage applied to the two ends of the corresponding colored light groups H1 and H2.

As the rhythm of the beautiful music rises and falls, the green and red sets of colored lights will flash accordingly according to the frequency and strength of the music signal, emitting constantly changing colors of light.

Component Selection

VS1 and VS2 use BCR3AM-6 type (rated on-state average current It=3A, off-state repetitive peak voltage Udrm≥400V) bidirectional thyristors. The parameters of the two tubes are required to be as consistent as possible. An aluminum heat sink needs to be installed when used at full load (500W).

RP uses a common potentiometer with a nominal resistance of 4.7kΩ. C uses a non-polar electrolytic capacitor, or two common 10μF electrolytic capacitors connected in series with opposite polarity. The wiring is shown in the figure below. L is replaced by the primary winding of the output transformer commonly used in pocket radios (inductance of about 70-100mH). T can be a small push-pull output transformer commonly used in transistor radios, and the insulation performance between the primary and secondary is required to be good.

H1 and H2 colored light groups can be formed by connecting commercially available 220V, 25W tungsten filament bulbs in parallel, with a maximum of 20 bulbs in each group. You can also use commercially available "Starry Sky" holiday flashing colored light chains (bulbs are covered with plastic flowers, 20 in each string, working voltage is AC 220V) to connect one or more strings in parallel to form H1 and H2 colored light groups, which is more conducive to forming various complex patterns and decorating and beautifying the environment.

Before use, the first small bulb with a bimetallic strip (originally used to control the self-flash) in each light chain should be replaced with an ordinary spare bulb to prevent the colored light chain from flashing automatically.

Production and use

The figure above shows the wiring diagram of the printed circuit board of the two-color music lantern. The actual size of the printed circuit board is about 70mm×45mm, which can be made by knife carving. The specific method is: cut a single-sided copper-clad board of appropriate size. Draw the copper foil lines according to the picture, use a knife (preferably the sharp end of a scrap steel saw blade) to cut and peel off the unnecessary copper foil; then use an electric drill to drill holes on the circuit board, and use a damp cloth with decontamination powder to polish the copper foil surface, apply a layer of rosin alcohol solution, and dry it before use.

As shown in the figure below, the soldered circuit board is placed in an insulated and sealed small box (such as a commercial soap box). The box panel has holes to fix the potentiometer RP and the terminals X1 and X2. The upper side of the box has holes to lead out the colored light groups H1 and H2 respectively with double-strand plastic sheath wires. The lower side of the box has holes to lead out the power plug XP through a double-strand plastic sheath wire about 1 m long. For ease of use, a four-pin terminal commonly used by electricians can be fixed in the box. It is used to connect the circuit board and the controlled colored light group.

Assembled circuits can be put into use without any debugging as long as the quality of components is guaranteed and welding is correct. If it is found that the flash and brightness of the green and red light groups are always very different (adjusting the potentiometer RP or the tone of the audio equipment is ineffective), or one of the light groups basically does not flash, the frequency of the circuit crossover point can be changed by appropriately increasing or decreasing the capacity of the capacitor C or the number of turns of the inductor L, thereby strengthening or weakening the flash intensity of the corresponding light group, so that the flash and brightness of the two light groups reach a satisfactory level.

When using, first connect the terminals X1 and X2 to the two ends of the speaker through wires, and insert the power plug XP into the 220V AC mains socket; then, under the condition that the speaker plays music normally, adjust the resistance value of the potentiometer RP until the green and red light groups flash brightly with the rhythm and frequency (tone) of the music. Note: The printed board is connected to the mains, and safety should be paid attention to during debugging and production.