# How to generate 30Hz sine wave?

I'm building a voice ring modulator. Part of it involves a 30Hz carrier sine wave to modulate the voice with. Since I'm trying to build a portable device it will be DC powered, and since a function generator is not really portable or DC powered, I don't thinks that's an option.

Crystal oscillators work at the MHz range so I'm guessing that's not the way to go either. I could play a 30Hz wave on an old mp3 player and use the audio output, but if there's another way involving analog components that'd be much better. There's no need for a lot of accuracy, just any wave from 20-40Hz will probably do, I would say it doesn't even need to be really stable either.

What approach can I take?

• You're looking at the wrong kind of function generator. – Ignacio Vazquez-Abrams Aug 4 '13 at 0:14
• What do you mean? – freejuices Aug 4 '13 at 0:18
• google.com/search?q=function+generator+circuit – Ignacio Vazquez-Abrams Aug 4 '13 at 0:26
• One thing worth adding to the question is what sort of accuracy you need, would say 5% drift be OK or are you after something more precise? – PeterJ Aug 4 '13 at 0:28
• Ignacio, thank you, but the idea of this post was that I didn't want to build a whole function generator. I just need this sine wave, i was hoping it would be easier than building the whole generator. Peter, that's a good idea, it doesn't need to be accurate at all, i'll add it to the post. – freejuices Aug 4 '13 at 0:39

Uses just opamps and resistors/capacitors. produces very clean sine waves in the low frequency range. There are many variations, with C=C1=C2, R = R1=R2, it oscillates at $f = \frac{1}{2\pi RC}$. Rb is a lamp used for temperature Compensation, although there are many variations don't require it, for instance, using zener regulators like such.