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Capacitors...Again

Muhasaresa

Jan 2, 2012
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Hi everyone :D

I'm afraid its another capacitor question from me....:rolleyes:

I have a 555 square wave of around 1000 - 2000 hz (controlled by a potentiometer) that go to some speakers. Between the 12V and Ground I have a 470uF capacitor. When it is there, and when I turn the potentiometer handle, there is a nice smooth transition between the tones.

However, when I rip the capacitor out and vary the potentiometer, the difference in tones are CHUNKY and only change to a few fixed notes (musicians: it actually is a minor arpeggio!).

Why is there such a massive difference? Is it something to do with them smoothing out fluctuations?

Thanks for the help,

Muhasaresa
 

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GreenGiant

Feb 9, 2012
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it seems that the 12V source is not a very clean /constant voltage

The cap is just helping keep it a smooth constant voltage, and eliminating noise

Just out of curiosity why do you want to rip out the capacitor?
 

Muhasaresa

Jan 2, 2012
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I am sorry I just realised I made a typo: I am using a 9V battery to power the system, but even so there should not be such an enormous fluctuation to affect the tone so much.

When I say I "rip" out a component, I just emphasise that I take it out of the circuit :D

I have attached a diagram to illustrate exactly what the problem is:
 

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GreenGiant

Feb 9, 2012
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that is a little weird, I still think its just a voltage fluctuation from when the timer and the resistor and the speaker draw from the battery

Thats the best answer I can give you
 

Resqueline

Jul 31, 2009
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The (8 ohm?) speaker probably represents a very heavy load for the "super heavy duty" transistor battery (?) you're using.
The rapid and large fluctuations you then get in the supply voltage to the 555 upsets its voltage-dependent timing circuit.
If you had used a high-impedance speaker &/or an alkaline battery you would not have noticed any difference with or without the capacitor.
The presence of the capacitor negates the (high) internal series resistance in the battery, on a short-term basis (milli-seconds).
 

Rleo6965

Jan 22, 2012
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Why don't you have capacitor connected to pin2 of 555 to gnd? Tis is suppose to be astable oscillator. Right?
 
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