Dual LED Flasher

 
 

          The circuit above is actually a multivibrator, i.e. a free-running miltivibrator. It's identical to a flip-flop that triggers itself repeatedly. Q1 and Q2 are general purpose PNP transistors (2N3906, 2N2907, etc). R1 and R2 limit the current to the LEDs (which flash alternately). Increasing the values of C1 and C2 will slow the flash rate.


   

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Metronome

 
      

A metronome marks time by producing a regular sequence of "clicks" or "pocks". Adjust the click rate by adjusting R2 or changing C1's value. That will varying the RC time constant so it will also varying the "delay time" of the buzzer or speaker. This project is so simple, applicative and low-cost. It is suitable for you who loves to learn about music and build and use this project for your low-cost metronome. :-)



    

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Light Flasher

 
         

This circuit produces bright flashes every second or so. R1 controls flash rate. L1 can replace with 3V or 4.5V flash light or for simply you can use a LED for example.

 

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Zener Voltage Regulator

   
       

This circuit supplies a steady voltage (V_out) to a load from an unregulated supply (like a battery), V_in can vary but must be at least 1 volt above desired V_out. I, can vary from 0 mA to planned maximum value. I does not change if I_L falls to 0 mA. Since I = I_L + I_Z, I_Z rises as I_L falls. In other words, the regulator always uses the same current, even when the load is removed. Caution: D1 and R1 must have proper power rating. Use Ohm's Law.


Example:

A radio draws from 20 to 50 mA from a 9 volt battery. To power it from a 12 volt batery, use a 9 volt, 1/2 watt Zener Diode. R1 should be closed to 60 ohm and rated for at least 0.15 W.

     

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Voltage Doublers

  
    

  

These circuit approximately double an incoming AC voltage. The output is DC. Use capacitors and diodes rated for twice the input voltage. Output ripple can be reduced by using large values for C1 and C2.


  

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