What device needs to be added to a circuit to provide frequency adjustment?

Question

And what type of circuit can this be added to, for example does anyone know of any circuits that take frequency adjustment devices, does any of the picaxe circuit boards take frequency adjustment devices. I need a circuit that can be used as a driving circuit and so I need to have a device on that circuit that can control frequency?

Answer 1

A tuning/LCR Circuit should be required, which is an inductor, capacitor and resistor in either series or parallel :



In the series one, Z is the impedence, which is equal to

(R^2 + xL^2 - xC^2)^1/2 when impedence is equal to R then current is max so at a particular frequency, depending on L,C the current is max also the resonant frequency.....so as u rotate the plates of a variable capacitor (which is wat u need) ure changing resonant freq so tuning , i think .



this site should be helpful if ure doing a project pn circuits:

http://www.kpsec.freeuk.com/study.htm

Answer 2

Look here: http://www.doctronics.co.uk/555.htm



This astable circuit uses capacitors and resistors to control frequency. Varying either will change the frequency, Variable resistors are usually cheaper than variable capacitors but the choice is determined by the required range, stability and sensitivity required.



Martin

Answer 3

A tuned circuit can be used with variable capacitor as is done by tuner in radios,

Answer 4

i always thought that a frequency generator alone is enough.