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LM555 as variable frequency oscillator
LM555 as variable frequency oscillator
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Old 16th June 2009, 05:18 AM   #1
xyz9915 is offline xyz9915  Pakistan
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Default LM555 as variable frequency oscillator

I need a circuit in which the frequency of LM555 astable multivibrator can be controlled externally I mean by the help of transistor etc. So, please guide what modification may be done in the attached circuit
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Old 17th June 2009, 12:10 PM   #2
bwaslo is offline bwaslo  United States
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LM555 as variable frequency oscillator
Look into replacing resistors with something like MCP4012.

If you want voltage control, don't use a 555, use a CD4046/74HC4046, a better chip for a variable oscillator, anyway. Use 555 only if you need to vary duty cycle. For most audio uses you'll want 50% duty cycle and something like the 4046 is more appropriate and has more versatile control.
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