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Voice pitch

Discussion in 'General Electronics Discussion' started by florinanghel, Aug 5, 2010.

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  1. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    I'm trying to make a voltage controlled oscillator or some other similar device that can change the pitch of a voice. I found a schematic here, but there's no values given. The voltage can be anywhere from 1.5 to 12 volts, as long as the speaker output is similarly loud as a regular voice. The frequency? About 20 to 500 Hz (preferably controlled by a potentiometer).

    I know there's much more circuits available on the Internet, but I'm trying to build it using simple parts. Timers, for example, are excluded. I appreciate any help. Thanks in advance!
     
  2. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    you may need to rethink your circuit. A vco, is an oscillator where the principal variable or tuning element is a varactor diode. The vco is tuned across its band by a "clean" dc voltage applied to the varactor diode to vary the net capacitance applied to the tuned circuit.

    These types of diodes work on the principle that all diodes exhibit some capacitance. for instance a Zener diode may have a capacitance of 65-85 pF at 0V and measured at 1 Mhz.

    Several obvious advantages come immediately to mind, a small transistor type package, very low cost, ease of construction on a circuit board, can be mounted away from heat generating devices, frequency determining circuitry entirely dependent upon resistor values and ratios, DC voltage control can be either from frequency synthesiser circuits or perhaps a multi-turn potentiometer. Such a potentiometer aids band spreading and fine tuning if two potentiometers are used.

    Are the Specifications of this project fixed, or are you simply trying to create your VCO using simple a cheap methods??

    You could maybe try using a 555 timer altho the output will probably be the inverse of what you want.
     
  3. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    The only things that must be exact are the voltage (not higher than 12v) and the frequency (the range of the human hearing: 20 - 500 Hz). The circuit has to change the speaker's voice to a higher or lower pitch.

    The problem with the 555 timer is that there's no specialized electronics store around (at least none that I know of), so I'm afraid I can't find complex parts.
     
  4. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    The range of human hearing is 20-20000 Hz.

    Well a VCO basically consists of an amplifier that provides adequate gain and a resonant circuit that feeds back signal to the input. Oscillation occurs at the resonant frequency where a positive gain arises around the loop. When part of the resonant circuit's capacitance is provided by a varactor diode, the voltage applied to that diode varies the frequency.

    I would suggest looking into amplifier circuits and determining the equations for gain etc... also check out LC Ocilators as i believe this is the type you require.

    Good luck!!

    Rob
     
  5. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    Yeah, I know that what I said wasn't the actual range of human hearing, but I was interested more in the range at which the human can produce sounds (aka frequency range of human speech). So my bad.

    The rest... I didn't get a thing from what you just said. I'm a beginner with electronics. :D

    Later Edit: I was thinking about an LC oscillator (even though I didn't know it was called like that), but I though it's just one of those beginner-with-no-understanding-of-things idea. I guess the capacitor would need to have a really low capacitance in order to create a 20-500 Hz oscillation. While for the circuit, I'll try to sketch something and post it here to see if I got the idea...

    Even Later Edit: I attached the circuit (no numbers though). Would this work?
     

    Attached Files:

    Last edited: Aug 5, 2010
  6. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Ok i understand what you mean now. Here is basically how an LC oscilatior works. (to give you an understanding of how each component works within the circuit.)

    Suppose a capacitor is charged by a battery. Once the capacitor is charged, one plate of the capacitor has more electrons than the other plate, thus it is charged. Now, when it is discharged through a wire, the electrons return to the postive plate, thus making the capacitor's plates neutral, or discharged. However, this action works differently when you discharge a capacitor through a coil. When current is applied through a coil, a magnetic field is generated around the coil. This magnetic field generates a voltage across the coil that opposes the direction of electron flow. Because of this, the capacitor does not discharge right away. The smaller the coil, the faster the capacitor discharges. Now the interesting part happens. Once the capacitor is fully discharged through the coil, the magnetic field starts to collapse around the coil. The voltage induced from the collapsing magnetic field recharges the capacitor oppositely. Then the capacitor begins to discharge through the coil again, generating a magnetic field. This process continues until the capacitor is completely discharged due to resistance.

    Technically this basic LC circuit generates a sine wave that loses voltage in every cycle. To overcome this, additional voltage is applied to keep the oscillator from losing voltage. However, to keep this oscillator going well, a switching method is used. A vacuum tube (or a solid-state equivalent such as a FET) is used to keep this LC circuit oscillating. The advantage of using a vacuum tube is that they can oscillate at specified frequencies such as a thousand cycles per second.

    Unfortunatly i do not have any circuit design software on this computer so i can not hook one up for you. However i believe your circuit will work however you must pay very close attention to component values in order to get the right frequencies you require. also you may wish to hook up a low pass filter that attenuates any frequencies above 500 Hz. this should be connected as in this link -

    http://image.absoluteastronomy.com/...ages/1/1s/1st_order_lowpass_filter_rc.svg.png

    with the resistor being - 10ohms and the cap being - 30uF.

    Also you may wish to amplify the signal before you output it to the Speaker. as before i have no design software with me atm however get back to me when u have hooked this up and i will send u all i have on op amps to help you along.

    Hope this helps,

    Good luck!!
     
  7. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    Thanks for your help. I'm going to start doing some calculations and stuff and, hopefully, come up with the right values for the components.

    I won't really mind if I'll get a frequency than 500Hz, I'll simply reconfigure the variable capacitor to an accepted value.

    Speaking of capacitors, is there a formula for how fast a capacitor can charge / discharge? After all, this timing here is the key.

    And one more thing. Shouldn't I reverse the order of the speaker and inductor? Or is that the right alignment?

    Thanks again for helping me out.
     
  8. rob_croxford

    rob_croxford

    262
    0
    Aug 3, 2010
    Here is quite a good article on charging and discharging of capacitors:
    http://www.tpub.com/neets/book2/3b.htm

    Your Inductor should be in parallel with your Capacitor with your output (in schematic view) should be in parallel with the inductor. so yes you do need to change the placement of your speaker like this (appologies for the poor diagram use)

    power supply|==Cap==Ind==OUT
     
  9. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    Okay, thanks. Great site.
     
  10. maha22

    maha22

    3
    0
    Aug 7, 2010
    Lucky for you i'm amazing at vegas. first, this is extremly hard to explain without video or pictures, so im going to try me best

    first, select your audio track, then on the very left hand sign, theres some icons. hover your mouse over each one, and select the one that says "track fx" (its green)

    a box will pop up. in the top right of that box, there will be some more green icons.hover your mouse over those, and click on the one that says "track fx"

    click on it, and another box will pop up, with a list of all the different effects. choose the one that says "pitch shift" (double click it) then click "ok"

    another box will pop up. now drag the top slider to 3-10 depending on how high you want your voice to sound. check "preserve duration" then click ok.
     
    Last edited by a moderator: Aug 7, 2010
  11. florinanghel

    florinanghel

    55
    1
    Jun 14, 2010
    @maha22: You obviously didn't read the previous posts. Who the heck's talking about software here? Hello! Real time voice pitch change via hardware says anything to you? And I don't think I said high pitch anywhere. I want both high and low.

    Sorry guys but this seems to much like spam to me. Seeing that Resqueline had to edit it for "Reason: Spamming" makes me 100% sure of it.
     
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