Byron J.

Member Since: September 10, 2013

Country: United States


Apparently, the J is for JFET.

A few thoughts on prototyping and breadboarding

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Demonstrating a Teensy Audio-based drum machine.

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Rather than a lengthy exploration of a single subject, I'm going to touch on a couple of smaller dishes.

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I've got a project on my workbench that I was hoping to share, but I met some unexpected difficulty along the way.

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A different approach to the problem we solved last week

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Embedded Micro's new IDE and the Lucid language.

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Thoughts and ramblings about numbers, plus an interesting discovery.

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Examining one of the categories that occupies significant space on my workbench: wire strippers.

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Drive the Moog Werkstatt-01 with the SparkPunk sequencer, and starting in on a MIDI-to-CV converter.

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Experimenting with optics and imagery.

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Tsunami Hookup Guide

February 16, 2017

Hit the ground running with Tsunami, the Super Wav Trigger.

LP55231 Breakout Board Hookup Guide

November 3, 2016

Get to know the LP55231 9-channel LED driver., and learn how to configure and program this surprisingly flexible IC.

Proto Pedal Assembly and Theory Guide

September 22, 2016

Getting started with the SparkFun Proto Pedal. We'll assemble the board, then discuss some of the details of the circuit.

Proto Pedal Example: Programmable Digital Pedal

September 22, 2016

Building a pedal around the Teensy 3.2 and Teensy Audio shield. Changing the effect in the pedal is as easy as uploading a new sketch!

Proto Pedal Example: Analog Equalizer Project

September 22, 2016

Building a gyrator-based analog equalizer using the Proto Pedal.

Proto Pedal Chassis Hookup Guide

September 22, 2016

Prepare the Proto Pedal Chassis by drilling holes for controls and painting it.

Hobby Servo Tutorial

May 26, 2016

Servos are motors that allow you to accurately control the rotation of the output shaft, opening up all kinds of possibilities for robotics and other projects.

Servo Trigger Programming Guide

May 26, 2016

Looking under the hood of the Servo Trigger -- using the development environment and some finer details of the firmware.

Continuous Rotation Servo Trigger Hookup Guide

May 26, 2016

How to use the SparkFun Continuous Rotation Servo Trigger with continuous rotation servos, without any programming!

Button Pad Hookup Guide

January 7, 2016

An introduction to matrix scanning, using the SparkFun 4x4 Button Pad.

Discrete Semiconductor Kit Identification Guide

November 19, 2015

Get to know the contents of the SparkFun Discrete Semiconductor Kit.

Preassembled 40-pin Pi Wedge Hookup Guide

October 29, 2015

Using the Preassembled Pi Wedge to prototype with the Raspberry Pi B+.

Raspberry Pi SPI and I2C Tutorial

October 29, 2015

How to use the serial buses on your Raspberry Pi.

MIDI Tutorial

October 8, 2015

Understanding the Musical Instrument Digital Interface.

MIDI Shield Hookup Guide

October 8, 2015

How to assemble the SparkFun MIDI Shield, plus several example projects.

Capacitor Kit Identification Guide

October 1, 2015

Learn how to identify and use a variety of capacitors using the SparkFun Capacitor Kit.

8-Pin SOIC to DIP Adapter Hookup Guide

August 13, 2015

Assembly and application of the 8-pin SOIC-to-DIP adapter.

Rotary Switch Potentiometer Hookup Guide

April 30, 2015

How to use the Rotary Switch Potentiometer breakout board, with some sample applications.

MP3 Player Shield Hookup Guide V15

April 6, 2015

How to get your Arduino groovin' using the MP3 Player Shield.

Servo Trigger Hookup Guide

March 26, 2015

How to use the SparkFun Servo Trigger to control a vast array of Servo Motors, without any programming!

Pi Wedge B+ Hookup Guide

December 18, 2014

How to assemble and start using the Pi Wedge to prototype with the Raspberry Pi B+.

Decade Resistance Box Hookup Guide

December 4, 2014

How to assemble the decade resistance box, then use it as a design and measurement tool.

SparkPunk Sequencer Hookup Guide

August 14, 2014

How to assemble and use the SparkPunk Sequencer kit.

SparkPunk Sequencer Theory and Applications Guide

August 14, 2014

Examine the inner workings of the SparkPunk Sequencer, then explore some modifications and alternate applications.

SparkPunk Hookup Guide

June 12, 2014

How to assemble and modify the SparkPunk Sound Generator kit.

Pi Wedge Hookup Guide

May 29, 2014

How to assemble and start using the Pi Wedge to prototype with a Raspberry Pi.

Large Solderable Breadboard Hookup Guide

February 27, 2014

This breadboard has a couple of tricks up it's sleeve!

Sound Detector Hookup Guide

February 27, 2014

The Sound Detector is a microphone with a binary output. This guide explains how it works and how you can use it in your projects.

VKey Voltage Keypad Hookup Guide

February 13, 2014

A quick hookup for the VKey analog voltage keypad.
  • The first thing to try is just hooking it up. Sometimes it’ll just work at 3.3V.

    Since the Due has regulated 5V available, you could use a logic level converter to step the 3.3 up/down to 5V.

    A typical MIDI current loop circuit puts about 5 mA into the LED of the input optoisolator. So we can scale the resistors on the output port to get more current from a 3.3V supply. If you make Rs and R4 each 80 Ω, then it’ll still put 5 mA into the receiver.

    Since the LED in the input port is part of the sender’s current loop circuit, the 220 Ω should be fine there (R1), as long as the opposing port is driving it with 5V.\

    Update: I just took a closer look at things. The Due should be providing 5V to the shield, but the documentation states the following:

    Warning: Unlike most Arduino boards, the Arduino Due board runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Applying voltages higher than 3.3V to any I/O pin could damage the board.

    The concern here is the incoming signal which comes from the optocoupler that is powered by the 5V line: it’ll try to drive the RX line to 5V. You can insert a logic translator (or even a resistor divider) there, or cut the VCC trace that leads to pin 8 of the optocoupler, and tie it to the 3.3V rail instead.

    The output side should be OK, since there’s the 741g125 transmission gate that can perform the 3.3V to 5V stepup, if the 5V line of the shield is indeed powered by 5V from the Due..

  • Try them in an IC socket, and you’ll understand their value.

  • There are a number of ways you can add more I/O pins using some external logic chips.

    The SX1509 is a 16-channel I/O expander, that interfaces using I2C. It has a mode that can scan an 8x8 matrix all by itself. They also have configurable addresses, so you can chain up to four of them on the same I2C bus.

    A little more primitive than that, you can use various discrete logic solutions to tack on more I/O. A 4-to-16 multiplexer can turn 4 outputs bits into 16 one-hot bits. Shift registers, like the 47hc165 and 74hc595 can add 8 digital inputs or outputs. With a little glue logic, you can tie them to the processor using SPI. For driving the LEDs, a high-power shift register, like the TPIC6B595 would work better than plain CMOS.

  • That was one of the yak-shaving diversions I just didn’t have time to write up.

    It was actually problematic to test the stereo indicator lamp – we’re under a big metal roof here, and don’t easily get reception. I wound up stringing about 25 feet of wire on the FM antenna input in order to get strong enough reception to get stereo to demodulate, and even attempt to turn the light on.

    Ultimately, it got a little assembly with two LEDs and two resistors all in series, a doubled up version of the ones pictured.

  • Can you describe what you’re doing in a little more detail? I’m not sure I follow what you’re doing, as the Sound Detector doesn’t have any speakers.

  • Some ideas, in no particular order:

    • Find something broken and fix it (like this receiver).
    • Come up with a task you want to accomplish, and research how to do it.
    • Build some kits (this is probably the shortest path to success).
    • Go hang out at a hacker/makerspace.

    Really, it comes back to where your own interests and aptitudes lie!

  • Yes, I was very careful doing the analysis, before making these changes.

    You can get the service manual and schematic from the link in the article. The most exotic semiconductors are JFETs in the AM receiver and FM muting circuit. Tons of diodes and BJTs.

    I also took the time to verify that the schematic and the unit were the same. I traced the wires downstream of the secondary, to make sure there wasn’t a path to some other part of the circuit that wasn’t reflected in the schem, and that ground didn’t show up somewhere unexpected.

    We also analyzed the 120 Hz flicker, and decided that it would be a higher quality solution to avoid it. Look at the lights while chewing a crispy tortilla chip, and it becomes discernible.

  • If the debug messages are printing, then you can be reasonably confident that the MIDI parsing is working.

    From the sounds of it, you might not have good communication to the DACs.

    I don’t recall anything out of the ordinary in getting them working, but it’s been quite a while.

    To test the DACs without any dependency on MIDI, there is the DAC Test Sketch.

    If you want to try it without an oscilloscope, slow the loop down by adding a delay() to it, maybe 5000 milliseconds (5 seconds). Then you can use a volt meter to check the DAC outputs. The one should gradually ramp up, and the other should ramp down.

    I’ve also improved the circuit a tiny bit since then, using a TL431 voltage reference to make a precise adjustable power supply for the Pitch CV DAC (those DACs use their VCC pin as the reference supply). I describe it in the last comment over here.

  • I’ve got some recommendations.

    At the entry level, Forrest Mims' books are one of the places I got my start. Many are smallish circuits that use only a handful of components. From the perspective of this blog post, the Op-Amp book is probably the most relevant.

    A step above that, the Art Of Electronics Student Manual is a pretty good guided tour through circuit design. This isn’t the 1000 page tome, but the companion volume, printed as a comb-bound lab manual. Each chapter breaks down an area of circuit design, and guides you through the solutions.

    I’m also a big fan of old National Semiconductor (now owned by TI) app notes. Lots of useful stuff in there. AN31 covers op amp circuits, and AN-32 covers discrete FETs.

    Eventually, you build up a mental catalog of circuits that you’re familiar with, and can combine into more sophisticated systems.

    Depending on your interests, you might be able to find literature that addresses it specifically. If you’re into guitar pedals, GeoFex and AMZ have some great analyses of FX circuits. If you’re into synthesizers, I’d recommend Electronotes.

    If you live near a university or community college, you might see if you can get into a class on introductory circuits.

    In tandem with any of these ideas, Bob Pease’s Troubleshooting Analog Circuits contains wisdom about how to approach things when the circuit on your bench isn’t working as intnded. Bob is a very engaging author – this one is a lot more engaging and relatable than the title makes it sound.

  • It is a bit of a chicken and egg problem.

    How do you draw a schematic if you don’t know the circuit works? How do you build a working circuit if you don’t have a schematic?

    The answer might look like: Start with something you know, and iterate from there. Reinforce the iteration by working orthogonally in different disciplines. Simulate a little, breadboard a little more, take notes as I progress.

    (Going through this process, I tried to use Fritzing for that placement diagram, and it felt like I walked off the end of its capabilities. Too many dense components. The graph paper was a fallback.)