How to generate the sound of a certain frequency?

Replies

• 

  reachrkata

  I think this link gives a circuit to you without the need of Schmitt triggers -
  
  PDF
  
  - Karthik
• 

  nucleuz

  Its not very difficult
  it actually very easy project.first try to make a so many square wave of different frequency with the help of micro controller.U can adjust the frequency by changing the delay time. Connect the port pins to speaker with the help of push buttons.if u generate 10 square waves u can hear 10 different sounds.
  
  Regards
  Jishnu
• 

  Angello

  Thanks a lot lads for the help. I have to think a little bit more about what you said and posted me😉
  Can you also explain in simple english what Schmitt trigger does?
  
  Thanks
  Patryk
• 

  nucleuz

  Schmitt trigger is a simple circuit.U r having a analogue signal.
  
  Here U is the Signal.And the red line show the threshold line.A is the Schmitt trigger output.
  working principle is very simple .when ever the input voltage cross the threshold voltage then the output will go to high.And when ever the voltage goes down to threshold voltage the out put will go to low.
  
  Regards
  Jishnu
• 

  Angello

  So basically it changes the out put depending on its input? So in a way it behaves like a logic gate?
  
  The picture on File:smitt Hysteresis Graph.svgis confusing me tho. Why A behaves like a threshold and B like and High-Low out put?
  
  And#-Link-Snipped-# is also Schmitt Trigger right? Why is there Vdd Vss going in there? Or is it overall a Schmitt Trigger?
  
  Ohh and by the way, what Vcc Vss Vdd Vee stands for? Or is it and old way to descried positive and negative terminals of voltage? I keep reading different things on net about this V's with different subscripts, which makes me even more confused. And I'm only a first year!😛
  
  
  Thanks Jishnu for all the explaining.
• 

  Angello

  Ok, so I got my frequency from 555timer, but it is a square wave and I need a sine wave.
  I was looking around the net for some schematics, but nothing specific really.
  
  I was thinking of using a bandpass filter - that what I found out could change square wave to sine wave, - but don't know how it should look like, what goes inside and what are values of either resistors, capacitors of inductors.
  
  Can anyone help me?
• 

  joshce

  This may be late but hopefully helps someone:
  
  A schmitt trigger compares the input voltage to two thresholds. When the input crosses the lower threshold the output goes low, when the input crosses the upper threshold the output goes high. The purpose is noise immunity of the input signal. Your output wont go high-low-high if noise pushes it passed one threshold voltage but not both. A regular comparator would!
  
  The V subscripts have to do with transistors. You have two kinds: Field-Effect Transistors (MOSFET- work with metal on semiconductors and electric fields) and Bipolar Junction Transistors (BJT- two semiconductor junctions pn and np). If you look in a electronics index for either term you will see the diagram. Vdd is the drain voltage of a MOSFET. Vss is the source voltage of a MOSFET.
  Vee is the emitter voltage of a BJT. Vcc is the collector voltage of a BJT.
  
  Here is a hint for the music:
  Octaves are at integer multiple ranges of 110 Hz. You can change between notes by adding exponentials of 2 such as:
  
  220*2^(0/12) = 220 - bottom of the octave
  220*2^(1/12) = 233 - note2
  220*2^(2/12) = 247 - note3
  220*2^(11/12) = 415 - top of the octave
  440 is the next octave because 220*2^(12/12) = 440
  
  Generate different tones at those frequencies.
• 

  Angello

  Joshce thanks a mil! At last I know what V's comes from😁
• 

  Tsardoz

  Angello,
  
  Try looking for a "sine wave oscillator" on internet. There is plenty out there. In all circuits there will be a couple of components that determine frequency. You can use switches to switch different components in and out of the circuit.
  
  If you want to filter a square wave to get a sine wave, you could look at using switched capacitor filters.
  
  Or a microcontroller is a neat solution. Then the project becomes a software one rather than hardware. There are plenty of ways to skin a cat.
  eg.
  #-Link-Snipped-#
• 

  Angello

  I got my freq with use of 555 timers. But another problem raised when I wanted to amplify these waves in an op amp to make them look more like ac current and also make it possible to hear them from speaker (and prevent burning the speaker with a dc).
  
  I use something like this :
  #-Link-Snipped-#
  Except with and output going to one speaker.
  
  The freq inferred with one another and and I got nothing(or maybe something like a white noise). Anyone can tell me why!?
  
  Another thing is described here:
  
  #-Link-Snipped-#
  
  please look at this and let me know for any possible solutions!
  
  regards
• 

  Van Helsing

  Some time ago there was an IC by Mostek the MK50240. This awsome IC generated a full octave from a single input frequency. By now I really don't have any idea the master octave is generated. Anyway, if you are interested in the math that make "sense" on music take a look at:
  
  Music And Mathematics
  
  This will explain why and how it works.
  Cheers.
• 

  Saandeep Sreerambatla

  I guess you have to use a amplifier which amplifies the sound depending on the frequency you need.
  
  Use a amplifier which uses BJT ,such that you can design it according to the requirements like frequency , noise level etc..
  
  IF you use MOSFET then noise will be pretty much lower! but its costy.