Sine/cosine DC circuit? - Page 1
Forum section: electronics / beginners

author: Grobalo
author_rank: Contributor
timestamp: October 26, 2013, 12:22:32 pm
content: Hi guys,I was wondering if it's possible to design a simple analog circuit that calculates the sine/cosine of the inputat DC.For example, we would get a constant output voltage V_out = V_in * sin(R), adjustable through a resistor R. So, it would work as a "sine response variable resistor".I only find oscillating circuit on the web. Any hint?Thanks!

author: fcb
author_rank: Super Contributor
timestamp: October 26, 2013, 01:05:35 pm
content: short answer: nolong answer: yes, but it's messy and not amazingly accurate - look up "sinewave shaper"

author: KJDS
author_rank: Super Contributor
timestamp: October 26, 2013, 02:01:49 pm
content: You could use a Taylors expansion of sine and the exponential performance of some diodes.The rest of the explanation is left as an exercise for the reader.

author: zapta
author_rank: Super Contributor
timestamp: October 26, 2013, 02:11:30 pm
content: You can use a micro controller with a/d input and d/a output.

author: c4757p
author_rank: Super Contributor
timestamp: October 26, 2013, 02:17:19 pm
content: Quote from: KJDS on October 26, 2013, 02:01:49 pmThere is a very good NatSemi app note on generating sine waves which describes this method. Sadly I do not recall the title or number, but I'm sure you can find it.

author: Crazy Ape
author_rank: Regular Contributor
timestamp: October 26, 2013, 02:21:16 pm
content: Might be this one.http://experimentalistsanonymous.com/diy/Schematics/Oscillators%20LFOs%20and%20Signal%20Generators/Sine%20Wave%20Generation%20Techniques.pdf

author: c4757p
author_rank: Super Contributor
timestamp: October 26, 2013, 02:25:30 pm
content: That's it. They have it configured for AC input, but that can be changed.

author: edavid
author_rank: Super Contributor
timestamp: October 26, 2013, 02:43:54 pm
content: The simplest way is to use an AD639(datasheet). They are obsolete, but you can get them on eBay.BTW, the National Semi app note is classic Jim Williams. It's really rude that they took his name off it.

author: c4757p
author_rank: Super Contributor
timestamp: October 26, 2013, 02:56:44 pm
content: They seem to leave names off most of their app notes, though, don't they?

author: Grobalo
author_rank: Contributor
timestamp: October 26, 2013, 03:15:20 pm
content: I think I'm going test the "Sine Approximation—Breakpoint Shaper" solution from the National Semiconductor application note you've linked.I'll also get a AD639 just in case, it can be usefull. But the former method seems more funThanks for all the replies!

author: edavid
author_rank: Super Contributor
timestamp: October 26, 2013, 03:17:30 pm
content: Quote from: c4757p on October 26, 2013, 02:56:44 pmThey took his name off after he left National.

author: Kryoclasm
author_rank: Regular Contributor
timestamp: October 26, 2013, 04:19:01 pm
content: What application would you use this for?

author: Crazy Ape
author_rank: Regular Contributor
timestamp: October 26, 2013, 04:21:27 pm
content: Quote from: edavid on October 26, 2013, 03:17:30 pmAnd then TI took National's name off the app note, what goes around comes around I guessIt's actually a revised version (April 2013). They've cleaned it up, added an index, dumped the two column text layout, etc. etc.http://www.ti.com/lit/an/snoa665c/snoa665c.pdf

author: Grobalo
author_rank: Contributor
timestamp: October 26, 2013, 06:24:24 pm
content: Quote from: Kryoclasm on October 26, 2013, 04:19:01 pmWell, I was reading thispost.Also, have a look atthis.Usually you plot one pair of variables on the scope, either (x, y), (x, z) or (y, z). But with a "Sine-cosine potentiometer" you canget a 3D imageon the scope.I simply want to replace the sine/cosine potentiometers by traditional potentiometers and some circuit and keep all this stuff analog.

author: Zero999
author_rank: Super Contributor
timestamp: October 26, 2013, 11:03:15 pm
content: http://sound.westhost.com/articles/sinewave.htm#s8

author: Rudolfo
author_rank: Contributor
timestamp: October 27, 2013, 07:36:34 am
content: Hi, here maybe a crazy option for generating sine/cosine from a potentiometer position - by using a single chip hall encoder. Small sine/cosine encoder iC, like the iC-MHA, outputs for 360 degree sine/cosine with 90 degree phase shift. They either look like a potentiometer, or can be build using one iC-MHA(http://www.ichaus.de/product/iC-MHA) and a small magnet on a shaft.

author: Zero999
author_rank: Super Contributor
timestamp: October 27, 2013, 11:20:23 am
content: http://www.sdiy.org/colbecklabs/circuits/triangle-sine.htmlhttp://electronicdesign.com/components/battery-powered-sine-generator-covers-100-hz-10-khzhttp://www.timstinchcombe.co.uk/synth/tri_sine/tri_sine.html

author: Skaface
author_rank: Contributor
timestamp: October 27, 2013, 11:33:29 pm
content: a lot of aircraft NAV indicators have DC sin/cos pots in them, maybe you could find a busted up one on ebay for the pot. Off the top of my head a King KI-203/204/206 and other have them