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# Help with wien bridge diagram

Discussion in 'The Projects Forum' started by hadoque, Jul 24, 2007.

Jul 24, 2007
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Hi
I'm very new to electronics, and I thought a fitting first project would be a Wien-bridge oscillator. Since I have a lm386 amplifier lying around, I thought I'd use the circuit discribed in the datasheet of this component (attached, see page 5). Now I have some questions about this diagram.
What kind of component is the round thing marked "ELDEMA CF-S-2158"?
What is $R_{L}$, $V_{S}$ and $V_{O}$?
What is the "Bypass"? What voltage should I use and where do i connect the output (speaker or whatever)?

Many thanks for help with answering these probably simple questions.

Jul 24, 2007
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Forgot the attachement...

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3. ### hgmjr Retired Moderator

Jan 28, 2005
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The round thing is a light bulb. It is used in this application because it exihibits negative resistance.

Vs is the positive power supply input.

Vo is the output of the oscillator.

hgmjr

Jul 24, 2007
10
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ok, thanks
what kind of bulb can I use? The specified bulb seems to be hard to get, aswell as any bulb with the 3V 15mA specs. Can I use a bulb with higher voltage or higher current?

Jul 17, 2007
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6. ### beenthere Retired Moderator

Apr 20, 2004
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Mouser carries lamps and has no minimum order. It is possible to substitute bulbs with different ratings by experiment. The filament voltage should be no more than about 15, and the rated current should be no more than 40 ma. You just have to find a resistor for the feedback that works with the bulb, using more current - smaller resistor as the basis.

Jul 24, 2007
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I live in Sweden, so I'd rather not order from the US. I found 3V 10mA bulb in sweden though, do you think that might work?

Jul 24, 2007
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Thanks for the help everyone. Here are some images of the final construction, it's working perfectly.

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9. ### DanRilley Senior Member

Jan 13, 2008
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This post is real old but maybe the poster still reads. Where do you buy bulbs from in Sweden? I'm also here and looking to complete the same project.

May 11, 2009
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# Why 2nd derivative is "squared" to represent wigglyness in GAM?

In David Miller's presentation (here, slide 21), he drew 1st derivative and 2nd derivative of a function. Then he said (slide 22) that grey part can is :

$$\int (\frac{\partial ^{2}f(x)}{\partial x^{2}})^{2}dx$$

My question is: the grey area should not have the "squared" to calculate its area, why not the below form:

$$\int (\frac{\partial ^{2}f(x)}{\partial x^{2}})dx$$

## 1 Answer

Consider one cycle of a sine wave: $$\sin(x)$$ on the interval $$[0,2\pi]$$. We can agree this is "wiggly", right?

The second derivative is $$-\sin(x)$$. Integrate that over $$[0,2\pi]$$ and you get zero "wiggliness".

The second derivative is squared so that concave and convex sections of the curve, which intuitively should both contribute equally to "wiggliness" if they are the same shape, both contribute equally to "wiggliness" if they are the same shape. Note also that the wiggliness is unaffected if the curve is flipped upside down--again, a property that you should like the measure to have.

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# A Construction Principle for Tight and Minimal Triangulations of Manifolds

@article{Burton2018ACP,
title={A Construction Principle for Tight and Minimal Triangulations of Manifolds},
author={Benjamin A. Burton and Basudeb Datta and Nitin Singh and Jonathan Spreer},
journal={Experimental Mathematics},
year={2018},
volume={27},
pages={22 - 36}
}
• Published 14 November 2015
• Mathematics
• Experimental Mathematics
ABSTRACT Tight triangulations are exotic, but highly regular objects in combinatorial topology. A triangulation is tight if all its piecewise linear embeddings into a Euclidean space are as convex as allowed by the topology of the underlying manifold. Tight triangulations are conjectured to be strongly minimal and proven to be so for dimensions ⩽ 3. However, in spite of substantial theoretical results about such triangulations, there are precious few examples. In fact, apart from dimension two…
7 Citations
Tight triangulations of closed 3-manifolds
• Mathematics
Eur. J. Comb.
• 2016
Efficient Algorithms to Decide Tightness
• Mathematics, Computer Science
SoCG
• 2016
This article presents a new polynomial time procedure to decide tightness for triangulations of 3-manifolds – a problem which previously was thought to be hard.
Separation-type combinatorial invariants for triangulations of manifolds
• Mathematics
• 2018
We propose and study a variation of Bagchi and Datta's $\sigma$-vector of a simplicial complex C, whose entries are defined as weighted sums of Betti numbers of induced subcomplexes of C. We prove
Golod and tight 3-manifolds
• Mathematics
• 2021
The notions Golodness and tightness for simplicial complexes come from algebra and geometry, respectively. We prove these two notions are equivalent for 3-manifold triangulations, through a
Average Betti Numbers of Induced Subcomplexes in Triangulations of Manifolds
• Mathematics
Electron. J. Comb.
• 2020
Upper bounds on $\sigma$ can be used to obtain lower bounds on the $f$-vector of triangulated $4$-manifolds with transitive symmetry on vertices and prescribed vector of Betti numbers.

## References

SHOWING 1-10 OF 37 REFERENCES
A CENSUS OF TIGHT TRIANGULATIONS
• Mathematics
• 2000
A triangulation of a manifold (or pseudomanifold) is called a tight triangulation if any simplexwise linear embedding into any Euclidean space is tight. Tightness of an embedding means that the
Tight triangulations of closed 3-manifolds
• Mathematics
Eur. J. Comb.
• 2016
An infinite family of tight triangulations of manifolds
• Mathematics
J. Comb. Theory, Ser. A
• 2013
Efficient Algorithms to Decide Tightness
• Mathematics, Computer Science
SoCG
• 2016
This article presents a new polynomial time procedure to decide tightness for triangulations of 3-manifolds – a problem which previously was thought to be hard.
The lower bound conjecture for 3- and 4-manifolds
For any closed connected d-manifold M let ](M) denote the set of vectors / (K)= (]0(K) ..... fd(K)), where K ranges over all triangulations of M and ]k(K) denotes the number of k-simplices of K. The
On Walkup’s class K(d) and a minimal triangulation of (S ⋉S)
• Mathematics
• 2013
For d ≥ 2, Walkup’s class K(d) consists of the d-dimensional simplicial complexes all whose vertex-links are stacked (d − 1)-spheres. Kalai showed that for d ≥ 4, all connected members of K(d) are
Rigidity and the lower bound theorem 1
SummaryFor an arbitrary triangulated (d-1)-manifold without boundaryC withf0 vertices andf1 edges, define \gamma (C) = f_1 - df_0 + \left( {\begin{array}{*{20}c} {d + 1} \\ 2 \\ \end{array} }