Variable ossilator - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 20, 2013, 04:44:21 pm
content: Hello i know you can buy fixed ossilators such as a crystal ossilator but are you able to make a variable ossilator?

author: Paul Price
author_rank: Super Contributor
timestamp: May 20, 2013, 04:48:21 pm
content: Yep!How to do this depends on the frequency range, quality and fidelity of the output of the oscillator, and how much time/money you want to spend to build such a thing.Cheapest way and a way to learn a lot about electronics: Buy a LM324 op-amp, a few resistors and capacitors.There are one chip solutions, such as am LM324 and one of it's op amps can be configured as a sawtooth generator and the sawtooth can be turned into a squarewave by another of the LM324 opamp sections, and you could easily modify the sawtooth generator to generate a linear ramp or even create a tunable filter from the remaining op-amp to make the sawtooth output look kinda sinewave-like in shape. You cam use a knob on a potentiometer to change frequency and you can also use a multi-pole switch to change frequency setting capacitors to have it work over quite a range of frequencies with a lot of resolution of your frequency control knob.Google it.Or else if you can go to an electronics store and buy an inexpensive 555 timer chip, see the attached .jpg

author: ddavidebor
author_rank: Super Contributor
timestamp: May 20, 2013, 04:58:20 pm
content: Sure, i made it with my mouthSeeTiiiiiiiiiic toooooooooc tiiiiiiiiic toooooooocTic toc tic tocTitoctitocIt's variable sir

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: May 20, 2013, 05:22:54 pm
content: Ok lets say a range of 1kHz to 35kHz ish

author: c4757p
author_rank: Super Contributor
timestamp: May 20, 2013, 05:25:35 pm
content: Quote from: ddavidebor on May 20, 2013, 04:58:20 pmYou, sir, are mean!The term you should search for is "VCO" or "voltage controlled oscillator". 1kHz-35kHz should be no problem at all.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 20, 2013, 06:39:13 pm
content: Oscillators can be generally divided into two styles: relaxation oscillators and resonant oscillators. Relaxation oscillators are like the 555. They are tuned by an RC network, usually by keeping C fixed and varying R. You can get a huge tuning range with a simple potentiometer. If you want to electronically tune it, you need some way of making a electrically variable resistor. A relaxation oscillator your best bet for a low-frequency oscillator with such a wide tuning range.Resonant oscillators use LC circuits (or equivalent: crystals use a mechanical "inductor"), which have a natural resonance, which is amplified and fed back onto itself to get a steady state behavior. These are usually tuned by varying C. Normally you use a varactor diode: a diode whose junction capacitance varies strongly with the DC voltage applied. LC resonators can also be tuned mechanically with a variable capacitor or inductor. LC resonators are more commonly used at higher frequencies, and varactors can't normally tune over such a wide range.

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 20, 2013, 07:12:19 pm
content: Quote from: c4757p on May 20, 2013, 05:25:35 pmI bet that when we apply some variable voltage on ddavidebor on certain places we can make him do that too.

author: c4757p
author_rank: Super Contributor
timestamp: May 20, 2013, 07:17:33 pm
content: Quote from: PA0PBZ on May 20, 2013, 07:12:19 pmOh, absolutely. I was bitten by a CRT anode once - pretty sure it both caused me to emit 35 kHz, and gave me the temporary ability to hear it.

author: dentaku
author_rank: Frequent Contributor
timestamp: May 21, 2013, 02:09:15 am
content: In the world of synthesisers it's pretty much always called a VCO (voltage controlled oscillator)It's probably easiest to use a 555 timer because you can get a large range of frequencies and there are allot of websites with instructions on how to set it up.One potentiometer (anything over 10k) will give you lots of control.If you want to make a rather crude oscillator just for fun out of even more basic parts you can build one with just 2 transistors, capacitors and resistors.http://wild-bohemian.com/electronics/flasher.htmlIt's called an LED flasher but there's no reason why you can't use it for other purposes.Replace the 100k resistors with potentiometers so you can control the frequency and smaller the capacitor the higher the frequencies you can make.Quote from: carbon dude oxide on May 20, 2013, 04:44:21 pm