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Switching Power Supply

Page history last edited by Noah Vawter 7 years, 1 month ago

  Complete Instruments      Instrument Bodies     MarkII

   Generators    Generator Electronics    Switching Power Supply

 

 

        Synthesizers         Synthesizer Controls

 

 

          Amplifiers     Loudspeakers   Resonances        Horns


 

Switching Power Supply

 

This is a simple switching chip that greatly increase the dynamic range of Exertion Instruments over linear regulators:   LM2574

 

Here is an engineering spreadsheet to configure the LM2574 to output precisely the voltage you want: 

 

These are some example schematics that I made for it that have been demonstrated to work well with exertion instruments.  For a diode, don't use the 1N4942 as suggested in the schematic below.  It's better to use this diode:  1N5817.    All resistors (R1, R2, and R3) should be 4.7K.  C1 can be from 100uF or greater.  Find what works best for your playing style. Larger values charge and discharge more slowly.  You can use low voltage capacitors here, because the voltage is not expected to go over 4V.  The switcher's output is configured for about 3.6V. 

Eagle CAD files if you want to make your own or edit it:

     bucking 03.sch

     bucking 03.brd

 

 

bucking 03 lasercutter.eps

 

 

 

 

 

The circuit in the schematic below is an improved piece of generator electronics.  This is an unregulated switcher.  Its function is to make the instrument as loud as possible while keeping the CPU running as long as possible.

 

It transfers electrical energy from the generator more efficiently than rectifier and AC Multiplier circuits.  It is being improved on this website as a group activity. 

 

 

In this circuit, each of the two phases of the stepper motor gets doubled then summed.  This is done so that the smallest body movements can generate sufficient voltage to make a sound, even if it's very quiet.  The difference between very loud sounds and very quiet sounds is usually important in music.  It is termed the dynamics of the music.

 

This circuit uses a 551 oscillator.  The 551 is low-voltage version of the 555 Timer.  It oscillates at about 200KHz and drives the base of a power transistor.  The base of the power transistor is gated all-on, or all-off.  This ensures that the transistor is operating in its most efficient region.  This is typical of power-switching circuits such as regulators and type D amplifiers. 

 

In this circuit, a TIP120 transistor switches the generator's current into the inductor for brief bursts (about 500 ns) and then disconnects the inductor for 4500ns. 

500 ns is long enough to establish a magnetic field in the coil.  In the 4500ns interval, the magnetic field in the coil induces a current in the wire which charges the capacitor.  The voltage in the capacitor is nearly insignificant - when the coil's current is released, it flows into the capacitor.  The only practical current limit arises from the internal impedances of the coil and the capacitor(s).

 

In this circuit, the output capacitance is actually a parallel combination of two capacitors:  One electrolytic and ceramic. This is done for extra efficiency.   The ceramic capacitor has a smaller internal resistance.  

 

This unregulated circuit has generated 50V unloaded with brief twists of the motor!  To continue progress, a second regulated output (3V) will be added to power a microcontroller.  In the future, the following self-interrupting oscillator will be evaluated for use in Exertion Instruments:  Oscillator with Super Low Supply Voltage

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