Showing posts from May, 2018

EAGLE PCB--Getting Rid of NAMES for Board Components

Full disclosure: 

I use Autodesk's Eagle for PCB layout.

So this blog entry will only be useful to you if you use Eagle vs. other means of laying out PCB's.

It will also only be useful if you use Windows; I suspect the Linux and Mac versions of Eagle are set up differently in terms of where the files go.

And-- I am using Version 9.0.1 of Eagle as I write this; Autodesk changes Eagkle all the time, so I can't guarantee this will help you if you're reading it 3 years from the date of this post.

If you don't know Eagle pretty well you want to skip this blog entry, it won't mean squat to you. But if you use Eagle all the time, as I do, it might be useful.  OK without a lot more blah blah:

Here is the issue.  

When I am designing a board layout, a series of Pads might look like this:

When how I want it to look is this (note the absence of what Eagle calls "NAMES")

Pads without names is useful in some situations--I can now use text tool on the tNames layer t…

One Cheap Arduino Nano Clone-o Plus one Cheap 1.8" TFT Display = An Entire Sunday!

Who can resist Amazon Prime Points?

Who can resist a cheap TFT display?  (I couldn't)

A million and one uses--as I develop my skills with Analog DIY and Digital hybrids I can justify all of this right?  (right???).

My goal this time: to design a simple DVM I can incorporate into audio gear. OF COURSE I can buy a DVM for like 25 cents that will probably work better.  And OF COURSE I already have  DVMs already. So why not stash one in my studio and use that.

(Answer: what fun would that be?)

Along the way, getting TFT displays going is an unfamiliar process for me, having never worked with a small display like well as understanding more about DACs, ADCs, and in general,  creating semi-precision applications--usually I just throw op amps at things and hope they work?

Anyway: these clones appealed due to their super low price ($6.50 US on a good day?), good online visibility and online .h libraries already written, like the Adafruit 7735 library

So just fire up an Arduin…

Random Resistance Vactrols--Creating a random CV generator with one--Rolling My Own Optoisolator--HowTO do this....

Howdy again!!! 

Can you say Vactrol?  Or Opto-Isolator? I just knew ya could....

In case you don't know what these are, take a look here.  The basic idea is that you power up an LED, which hits a nearby photo resistor; you use the resistor to control V- or current-to-resistance circuits, which of course, are at the heart of a lot of synth and pedal DIY.

And maybe more important? these are fun little doodads....use 'em for compressors, for trem pedals, for filters, and a lot of other things where you need to convert voltages or currents to resistance.

I have bought Vactrols and optos from surplus places like Electronics Goldmine and Small Bear in the past, and had hours of fun, but in this post I am going to cover how for I built some optos for myself out of junk bin parts.

Oh yeh!!  It was easy!

But!!  a few things about Vactrols before we go further:

There is a diode in one end, and like all diodes, if you push too much current through it, you blow the Vactrol up.There is a dio…

Arduino Random Gate for a Modular Synth--Design Phase....


I had an idea for a new circuit, inspired by the "source of uncertainty" thinking from the old Buchla designs of the 70's.  Design goals: a random 0V - 5V signal I can use for gates (for instance, triggering the sound of water dripping--that at times should be pretty random).  That's pretty easy.  For extra credit, also have a random CV out that matches the random gate.

I started to think about how best to put that together.

I can do that with analog circuitry and if I chose that route, many of the blocks below I already fabbed and tested working, in the form of small PCB's. For instance, a noise generator.  I have a working Sample and hold PCB as well, but haven't posted it yet....I will soon.....

I think the analog circuit would have to look like this:
With some tweaks I can probably get this work, but that's a lot of boards, and I wanted to keep the footprint for this project small--i.e., fit it in a 1U frac-rack which is something like 5.25&qu…



I started on analog stuff back in the 70's, moved to digital around 1988 or so?

And as an older tech guy have gotten back into the old analog circuits and sounds from when I was young.

Some of the goals for all of this:
Audio DIY is primarily a learning thing for me. I could buy some premade Eurorack VCO thingy for way less money than building it myself ("DIY") and it will probably sound and work better than anything I can come up with but that's OK. I have no formal training in physics, engineering or math. The little low frequency electronics knowledge I have was picked up mostly from my brother, whose an EE, reading books and the web, and what I can find on youtube. My college degree is in anthropology. but as they said in Animal House: "knowledge is good".  So yes I suck at a lot of this electronics stuff but want to get better at something (for a change). If I don't write this stuff down right away in a month I will never remember why I did x …