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Showing posts from June, 2018

Arduino based Random Gate generator--done-works

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I have been working on a PCB for my various Arduino projects including the Random Gate Generator...part I is discussed in this post.



ABOUT THE BUILD: I have fab'd up a prototype of a Arduino PCB that tries to be flexible and audio oriented, with accommodations for 6 op amps, and places to jam D/A, jellybean logic and so on. I used it as a home for the random generator.

The idea is to not have to fab up a new board for every Arduino project; most seem to be just Arduinos, DACs, and buffer op amps?

Anyway here's what I came up with:




The breadboard prototype is seen on top with working random gate.
I am starting to copy all the parts to the PCB.  Power supply (PAIA!) (+/- 15V) is in the bottom left.....
An hour or so later: Good news!  It all works!!!!  I have been having fun with this module, might build some more.

Arduino code can be downloaded at GitHub.
https://github.com/cslammy/arduino-random-gate

Schematic--note that after drawing this I added a reset switch that you'l…

9mm POTS--creating an Eagle Library

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(Advanced warning: If you don't use Eagle for schematic/PCB/gerber creation, this post will mean zilch....You have been warned....)

 I bought some dual concentric pots from Small Bear and needed it in the PCB for a few projects.  I couldn't believe I couldn't find an existing library (Alps?  Bourns? Adafruit?  Anyone?) that already had this part--this is super simple, just an array of 100 mil traces with proper spacing and some kind of tName silkscreening that works….but I couldn't.  Time to roll my own....

To summarize the very basics:  Eagle libraries have 4 components that all have to be created and linked properly to work in a useful library

Library: a set of devices.
Device: the entire component--a joining of a Package and Symbol
Package: what goes on your PCB.  Traces/drills etc. must be right or your part won't lay onto the PCB correctly after you fab.
Symbol: the image that goes on your schematic.

There are so many pages about creating Eagle libraries that I wo…

Synth DVM part III--VU blues

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This is the third entry about building a so called "Synth DVM".  If you are interested in the last 2 posts about this, here are links to part two and part one.

OK I have a working prototype on my bench, and I am having 5 boards made up for the op amps and Nano, from EasyEDA, they should be here next week.  Assuming that works I'll get a front panel made....

In the meantime I'm trying to finish up the TFT display programming for the project.  I am using the Adafruit GFX library, discussed in part two...

For the most part once I found decent code examples the TFT coding has been pretty easy, so I made it harder on myself--I decided that in addition to a simple voltage readout I want an analog looking "VU style meter" for the DVM, that shows a needle that points to -10V, 0V, 10V and all in between.
I can see reusing this for all sorts of audioDIY since the whole voltmeter thing with Arduino seems super easy--RMS conversion for displaying AC audio levels?  Ard…

Arduino based "Synth DVM" Part II

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You can see part I of this post, where I try to get the TFT screen going, as well as discuss this DVM synth project in general here:


To review:
I am working on a simple DVM so I can easily see control voltages without having to crack out my Fluke DVM or Siglent Scope.  This Arduino based DVM that can read positive and negative voltages relative to ground without having to flip switches or whatever.Works with a +/- 15V linear power supplyInput is buffered so nothing "upstream" can detect it's being detected.Able to read from -10V to +10V DC--with as small an error factor as possible--within say 100mV tops--less is preferred.Have the readout be on a TFT display that's mounted on a 2 or 3u FracRack panel so I can put that into a rack.Extra credit: be able to get P/P AC read as RMS voltage.  But for phase I, stick to DC. Since that last post I've spent time researching this (to paraphrase the immortal Don Lancaster: you can save hours at the bench by spending minutes …