I know there are tons of examples of music driven LED circuits out there, but they mainly control just one LED or one string of them. I want to make a circuit that will control quite a few LEDs, with each LED at a different range of frequencies.  To do this, I am planning on making an array of band pass filters. Each filter would drive a different LED (or string, or something else)... through a BJT perhaps? Here is a quick sketch of what I am thinking.  I might add in a high and low pass filter in the end, but I'll decide that later.  Anyway, would this work? I am wondering if you have advice for me, or maybe some different tricks that could reduce the complexity of this project. Are there certain things to watch out for, such as my source not being able to supply enough power to my filters, ect?  Thanks in advance! I really appreciate any help!
I want to create a circuit that can detect audio frequencies and flash RGB LEDs different colors depending on the detected frequency. The frequency range will be from 20 Hz to 12 kHz, after looking at the chart below.   (source: )    So my question is: what circuit design should I choose to make a good frequency detector? I suppose I would need    Preamp for the microphone (is it necessary for the ADC?) Band pass filters (active or passive?) A microcontroller with an onboard ADC that has a sampling rate of at least 24 kHz.   Before I get too excited, are there any circuits out there that already do this?
Show that if $(b,c)=1$, then $(a,bc)=(a,b)(a,c)$. Typing the ZIP code doesn't yield the company page List the files accessed by a program time is a brilliant command if you want to figure out how much CPU time a given command takes.  I am looking for something similar that can list the files being accessed by a program and its children. Either in real time or as a report afterwards.  Currently I use:  #!/bin/bash  strace -ff -e trace=file "$@" 2&gt;&amp;1 | perl -ne 's/^[^"]+"(([^\\"]|\\[\\"nt])*)".*/$1/ &amp;&amp; print'   but its fails if the command to run involves sudo. It is not very intelligent (it would be nice if it could only list files existing or that had permission problems or group them into files that are read and files that are written). Also strace is slow, so it would be good with a faster choice. The Nazgul are afraid of fire, but can they be harmed by it? When Aragorn and the Hobbits are on Weathertop, just after seeing the Nazgul below them and prior to inflicting Frodo's knife wound, Aragorn says the following:     Sauron can put fire to his evil uses, as he can all things, but these   Riders do not love it, and fear those who wield it. Fire is our friend   in the wilderness.   Is there any mention as to whether fire can actually cause harm to the Nazgul and if not, is there a specific reason for their fear of it? How can one prove that $\lim_{n \to \infty}a^{1/n}=1$ for every $a>0$? Prove that $\lim_{n \to \infty} a^{\frac{1}{n}} = 1$ if $a &gt;0$.  In my textbook, we are given a suggestion to let $a^{\frac{1}{n}} = (1+h_n)$ and then show that the $h_n$ term goes to zero using a Theorem that states the following conditions:  $\lim_{n \to \infty} = \infty,$ if $a &gt;1, 1,$ if $a = 1,$ and 0, if $\vert a \vert &lt; 1$. I apologize for not formatting the above cases appropriately; I could not figure out how to use a giant left brace to group them altogether.  If I rewrite it as $a^{n^{-1}}$, then I thought that this might help, but I don't think the Binomial Theorem would then apply since the exponent is negative. Furthermore, the problem is only concerned with the positive, real $n$-th roots. I am quite stuck on this problem and any suggestions or advice would be greatly appreciated.   I am using the textbook Introduction to Analysis by Arthur Mattuck. While browsing Stack Overflow, I noticed that I lost a lot of reputation:        Is this serial downvoting? Will it be corrected by a rep-recalculation? How often are those done?    Here's a second instance: How to kill a player when they touch a block? I am making a multiplayer parkour map on bedrock edition, and I have it set up where when a player steps on a grass block they die. But when a player steps on a grass block it just kills anyone who touches it.  First: A repeat command block (set to always active and unconditional)   execute @e [type=player] ~ ~ ~ testforblock ~ ~-1 ~ grass   And then I have a chain command block (set to conditional and always active)  kill @e [type=player]   And it does work..... IF in singleplayer only. (which is not at all what I want)  Thank y'all in advance. Is there a way to run Python on Android? We are working on an  version and this platform has a nice Python API..  However, there is nothing official about Python on Android, but since  exists, is there a way to let the snake and the robot work together?? GridBox/packed array behaviour What is the result of $ \lim_{n \to \infty} \frac{ \sum^n_{i=1} i^k}{n^{k+1}},\ k \in \mathbb{R} $ and why? What is the result of the next limit:   $$ \lim_{n \to \infty} \frac{ \sum^n_{i=1} i^k}{n^{k+1}},\ k \in \mathbb{R} $$  Why (theorem)? How to pad zeroes to a string? Definable real numbers Drawing a constant randomly distorted circle I am trying to draw a special and contradictive plot : A circle with random distortions which have to remain constant regardless of how many times I build the document.  An example of what I am trying to achieve can be seen below    This figure was produced with the following code  \documentclass{standalone} \usepackage{tikz}    \usetikzlibrary{decorations.pathmorphing}   \begin{document}     \begin{tikzpicture}         % axes         \draw[ultra thin] (-2.5, 0) -- (2.5, 0);         \draw[ultra thin] (0, -2.5) -- (0, 2.5);         % undistorted sphere         \draw[ultra thin, dashed] (0, 0) circle (2.25cm);         \draw[ultra thin, dashed, -&gt;] (0:0) -- (125:2.25);         \node at (-1, 1) {$R$};         % distrorted sphere         \draw[very thick] plot[domain=0:350,smooth cycle ] (\x:2+rnd*0.5);         \draw[very thick, -&gt;] (0:0) -- (45:2.1);         \draw[ultra thin, -&gt;] (1, 0) arc (0:45:1);         \node at (1.2, 0.4) {$\theta$};         \node at (0.7, 1.25) {$R(\theta)$};     \end{tikzpicture} \end{document}   The problem with the code is that whenever I make a change to it and rebuild the document, the "distorted" circle will have a different shape, since I am using the rnd function. The reason I would like to have a constant-random shape is because I would like to denote its radius at an angle θ, therefore it has to touch the outline of the circle.  Any idea on how to achieve such a thing? How to find regression coefficients $\beta$ in ridge regression? In ridge regression, the objective function to be minimized is: $$\text{RSS}+\lambda \sum\beta_j^2.$$   Can this be optimized using the Lagrange multiplier method? Or is it straight differentiation? Ping a site in Python? Suppose $53$ percent of the population prefer red socks to green. If $100$ random people are asked, what is the probability that most (at least $50$) will say prefer GREEN:  So I set \begin{align*} N &amp; = 49.5\\   n &amp; = 100\\   p &amp; = 0.47 \end{align*}  Then.. \begin{align*}    P(N \geq 49.5) &amp; = P\left(\frac{N - np}{\sqrt{npq}}\right)\\                &amp; \geq \frac{49.5 - 47}{\sqrt{100*.47*.53}}\\                   &amp; = \varphi(0.50)\\                   &amp; = 0.3085   \end{align*} Except, that's not the right answer. What did I do wrong in my calculations? Why Did Dumbledore Let Harry Give the Remains of the Diary Horcrux to Dobby? J.K. Rowling confirms that Dumbledore knew the destroyed diary was the remains of a Horcrux;     JKR: "In essence divided," exactly, the "essence" being the soul. So Dumbledore knew all along that he must have- well, he suspected until Chamber of Secrets, and then at the point where he saw what was clearly the remains of a Horcrux, in other words, the diary, he thinks, "Okay. There you go. And not only has he definitely done it, but he's got to have more than one, because he's treated this one very casually."      Yet Dumbledore allows Harry to take this very dark magical artifact and return it to Lucius Malfoy (in order to free Dobby):     ‘Professor Dumbledore,’ he said hurriedly, ‘can I give that diary back to Mr Malfoy, please?’   ‘Certainly, Harry,’ said Dumbledore calmly. ‘But hurry. The feast, remember.’   Harry grabbed the diary and dashed out of the office.   Chamber of Secrets - page 248 - Bloomsbury - chapter 18, Dobby's Reward   Why did Dumbledore allow Harry to take the Horcrux before he had fully examined it, especially as Dumbledore knew it was a Horcrux? The Peverell ring had a lethal curse placed on it for anyone who tried to put the ring on. Why didn't Dumbledore check the diary for additional curses or Dark Magic before giving it to Harry? I would have thought Dumbledore would have wanted to keep whatever Horcrux relics he found.   Also, do we know what happened to the diary after Harry gave it back to Lucius Malfoy and Lucius threw it aside? Are there any instances in canon that place the diary back in Dumbledore's hands? A command-line or batch cmd to concatenate multiple files I have 50 text files in one directory.  Is there a Windows command-line method to concatenate those files into a single file?  I am using .  I don't want to type the name of all files. How can I mine redstone ore? I found redstone ore in Survival Mode (Minecraft Pocket Edition) and tried to use all five tools to collect it. It took about a minute or two to break, but I couldn't collect anything from it once broken.  How do I mine redstone ore? How to calculate $\lim_{n\to\infty}(1+1/n^2)(1+2/n^2)\cdots(1+n/n^2)$?