Here is a simple circuit that can be pluged to the output of any stereo to make an instrument "dance" in the rhythm of the music.
The instrument used is a microammeter of 0-200 uA or close to it, since the design is not critical. This instrument, low cost, can even be taken advantage of some equipment that the player has out of use.
The circuit is connected in parallel with the output of the speakers of the two channels of the stereo (one for each if the unit is stereo if the player wants).
The only adjustment to be made is a trimpot whose purpose is to find the sensitivity of the circuit according to the power of the stereo. In figure 1 we have the complete diagram of the simple VU-meter.
The arrangement of the components on a terminal strip is shown in figure 2.
The set can be placed inside a plastic box or even adapted to the housing of the amplifier or sound equipment that the player has. In this case, it can be "embedded in the panel" or in another way, according to the taste of each one.
The diode supports equivalent 1N4148 or 1N4007. The trimpot is common, the resistor is 1/8 W or larger. Depending on the desired inertia or response speed of the instrument the capacitor C1 can be changed in the range of 1 uF to 100 uF.
It will be interesting for the reader to experiment because each instrument has its own characteristics and the capacitor helps to adapt the circuit. Electrolytics can have any working voltage from 12 volts.
To adjust the unit, connect points A and B to the output of your sound system (wires going to the speakers). Then, turn the volume up slightly and set P1 until the pointer gently swings to the beat of the song. If you notice that the pointer tends to deflect to the wrong side, reverse the M1 instrument connections.
Any microammeter with full scale between 100 uA and 0.1 mA can be tried.
MATERIAL LIST
D1 - 1N4002 or equivalent - silicon diode
P1 - 47k ohms - trimpot
R1 - 1 k ohms, 1/8 W - resistor - brown, black, red
C1 - 1 to 47 uF / 12 V - electrolytic capacitor
M1 - 0-200 uA - common micro-meter - see text
Miscellaneous:
Terminal strip, input terminal for connection (bridge with screws), mounting box, wires, solder, etc.
