Tutorials on Bald Engineer

Picking I2C Pull-Up Resistors (Correctly)

Thu, 07 Mar 2024 13:22:00 +0000

A long time ago, I made a video suggesting math was unnecessary to determine proper pull-up resistor values. Like most generalized statements, that suggestion is not always true. For example, in data buses like I2C, speeds like 400 kHz and 1 MHz are common. At those speeds, the pull-up resistor and the bus capacitance form an RC filter that fundamentally limits the data transmission speed. Or. It limits the range of pull-up resistor values. In this Workbench Wednesdays video, I show how to estimate I2C bus capacitance, measure that capacitance, and pick pull-up resistor values.

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7+ Python Engineering Modules for Electronics Engineers

Thu, 11 Jul 2019 12:50:23 +0000

Python is everywhere. Its capabilities continue to grow. Not only can you create simple scripts, but you can create full-blown applications with it. The core has been scaled down to run on 32-bit microcontrollers like the ESP32 and Adafruit Feather M0. You can even use Python engineer modules to design stuff like circuits. There are electronics Python modules that create schematics, simulate circuits, and make solving math a cinch. Here are some of the modules I found that make Python usable for (electronics) engineering.

7 MOSFET Myths and Misconceptions Addressed

Wed, 08 May 2019 13:03:24 +0000

The most popular AddOhms video is my short tutorial on MOSFET basics. In the years since I posted the video, people have sent me many questions. While answering those questions I’ve learned quite a bit as well. For example, in that video, I say that Vgs is the threshold to turn on the MOSFET. Well, it turns out, that is not entirely true. It is the threshold to turn it off! Oops. A minor point with a subtle difference, but a common MOSFET misconception.

Low side vs. High side transistor switch

Wed, 10 Apr 2019 13:45:02 +0000

A common task for a transistor is switching a device on and off. There are two configurations for a transistor switch: low side and high side. The location of the transistor determines the type of circuit and its name. Either transistor configuration can use a BJT or MOSFET. In this post, I draw the configuration for both transistor types, discuss which requires a driver, and explain why you would use either. If you are new to transistors, check out the resource links at the bottom. I have a few videos I made and some from element14’s The Learning Circuit, which do a great job introducing transistors.

Connect pins with KiCad Bus, Labels, and Global Labels

Wed, 21 Nov 2018 14:18:20 +0000

2020-04-04: This tutorial is based on KiCad 5. With KiCad 6, the bus feature works a little different (so I’m told.) When your schematic has a large number of related signals, it is helpful to group them. In its schematic editor, KiCad has a few tools to help. Your end-goal helps determine which tools to use. For example, do you need a KiCad bus or a label? In this post, I explore how you can define signals, group them, and reference them across schematic sheets.

Creating Custom KiCad Schematic Symbol in 5 Steps

Wed, 14 Nov 2018 14:21:23 +0000

A new project I have started working on involves the Apple IIgs. It was Apple’s last 16-bit (and 8-bit) computer. Inside are many application specific integrated circuits, or ASICs, that make the IIgs an extraordinary member of the Apple II family. One chip, in particular, is called the “MEGA-II.” This chip takes all of the individual logic chips from the original Apple II design and incorporates them into a single 84-pin PLCC.

Arduino millis() plus addition does not add up

Wed, 10 Oct 2018 13:00:23 +0000

In the past, I’ve covered how to reset Arduino millis() and have provided a growing list of examples using millis(). While reviewing the code for the elegoo Penguin Bot, I was reminded of a millis() mistake I see often: addition. The only way to properly handle millis() rollover is with subtraction. Let’s look at why (and how.) What is Arduino millis() The Arduino library has a function called millis() which returns the number of milliseconds the processor has been running. On other platforms, you might see references to a “tick counter.” It is the same idea. A hardware timer keeps incrementing a counter at a known rate. In this case, that rate is milliseconds.

Arduino MKR Vidor 4000 Hands-On

Wed, 15 Aug 2018 13:27:52 +0000

Earlier this week, I looked at the Arduino MKR Vidor 4000 during an AddOhms live stream. My goal was to understand the Vidor better. It is the new FPGA-based Arduino which started shipping this month. It runs about $60. You can learn more at the Vidor Product Page on the Arduino website. In this post, I briefly touch on the difference between an FPGA and a microcontroller. Then I walk you around the MKR Vidor 4000’s board. Using one of the examples, I talk a bit about how the various chips communicate with each other. This section also highlights what makes the Arduino FPGA board different from other development boards. Lastly, I answer “should you buy an Arduino MKR Vidor 4000?”

MKR 4000 VIDOR Hands-On Video | AddOhms Live

Tue, 14 Aug 2018 13:47:52 +0000

As promised, the Arduino team shipped the MKR 4000 VIDOR by the end of July. The graphical editor is still missing in action, but you can check out the board now. I received mine. In this AddOhms Live Stream, I turned it on and checked it out. This video is a “working” live stream. Generally, I try to set up some demos and run through some canned actions. Not this time. I used the board once, on another computer. You get to watch how I attack a new board…live! Warts and all.

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Standalone Arduino Turn-On and Debug

Mon, 09 Jul 2018 13:00:54 +0000

This AddOhms episode is part 3 of the “design your own Arduino” series. In this one I populate a bare PCB, reflow solder it, debug a few issues, and load the Uno bootloader. Originally, I designed 2 versions of the board. One version contained an error that I planned to fix in the episode. Well, turns out, the “correct” board had two issues which were more interesting. Check out the #27 show notes for links to a bunch of stuff in the episode, including the design files.

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Five Arduino math fixes for when it is wrong

Wed, 04 Jul 2018 13:16:52 +0000

While the Arduino library does an excellent job of hiding some of C/C++’s warts, at the end of the day, it is still just C/C++. This fact causes a few non-intuitive issues for inexperienced programmers. When it looks like Arduino math is wrong, it is probably one of these reasons. When people ask me for help with their programming, I check each of these Arduino math mistakes. If your code seems to be hitting a bug, check to make sure it is not how the compiler handles math.

Arduino EEPROM stores any datatype

Wed, 20 Jun 2018 13:00:46 +0000

Funny how a simple idea can spider out into multiple paths. Arduino EEPROM seemed like a straightforward concept. A few a years ago it was as easy as having either 512 or 1024 bytes of flash memory. The Arduino IDE offered an EEPROM library which let you read and write a single byte. Today, however, with many different processor architectures saving data to EEPROM varies. It is now possible to save any datatype to EEPROM but not on all boards and not all using the same method.

Learn Six Oscilloscope Measurements with an Arduino DUT

Wed, 13 Jun 2018 18:44:22 +0000

One of the best ways to learn how to use a new piece of test equipment is to use it. Sounds easy, right? The problem is, sometimes when you are in the middle of troubleshooting your circuit, figuring out what the knobs on your scope do is an immense frustration. Use these 6 oscilloscope measurements, and just an Arduino Uno, to learn how to use a new or unfamiliar digital scope.

5 LDO Regulator Considerations other than voltage and current

Wed, 30 May 2018 13:03:28 +0000

For an AddOhms series, I created a DIY Arduino I am calling the “Pyramiduino.” It is an ATmega328p based board in the shape of a triangle. Other than being cute, the shape does not offer any other benefit. The design features a 3.3 volt LDO Regulator, which is also the subject of this post. I forgot a fundamental aspect of design: read the freaking datasheet. The board’s LDO regulator was not turning on. Adding a passive scope probe to the circuit suddenly fixed the problem. The regulator turned on. When touching the enable pin, it measured about 1.25 volts. While I am sure Rohde & Schwarz would like me to ship scope probe with each board, that was not an option. With the impractical fix in place, I got to thinking about that voltage level. I remembered that the datasheet mentioned about 1.2 volts was needed for the “HIGH” threshold. Which meant, 1.25 volts applied to the pin enabled an active low input. Not only that, I remember the datasheet clearly said it had a pull-down resistor built-in. What was going on?

Picking Pull-Up Resistor Value | AO #25

Fri, 04 May 2018 21:14:16 +0000

Common question that comes up about pull-up resistors: what value do you pick and why not just use a piece of wire? In this follow-up electronics tutorial, the bald engineer looks at how to pick a pull-up resistor value. Note that while focused on pull-up everything said in this video would apply to pull-down as well. If you’re new to pull-up resistors, check out this longer Pull-Up Resistor Tutorial. Watch the full video

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Oscilloscope Probes Primer - Why so many types?

Wed, 02 May 2018 22:06:58 +0000

Unless you have a BNC or SMA connector your board, you will need a probe to get signals into an oscilloscope. Understanding what kind of oscilloscope probes are out there, which ones should you have for your scope and which ones to use for different measurements can be daunting. In this post, I look at some common scope probe types and offer some suggested measurements for each. Special thanks to Rohde and Schwarz for providing the equipment used in this post. You can learn more about their scopes and probes at rohde-schwarz.com . This post is not a comprehensive guide of oscilloscope probes. I am covering the types I have used. I do think this information should be enough to least form questions to ask your vendor before purchasing. Asking questions is important. If you have never bought specialized oscilloscope probes, you might not realize they can cost more than the scope itself. Maybe not an individual probe, but get one for each channel, and the cost rises. So picking the correct probe type is essential.

DIY Arduino PCB Pryamiduino (Video)

Wed, 28 Feb 2018 14:00:03 +0000

Continuing the DIY Arduino tutorial series, this AddOhms episode shows how to create a PCB in KiCad. I make a joke that the original design was a rectangle, which I found boring and pointless. So instead, I designed a triangle to give the board 3 points. Get it? Puns! I am calling it the Pryamiduino. To be honest, I found not having a constraint to be a problem. By forcing a specific board size and shape, many decisions were more manageable.

Debug SONOFF AC Relay with a Thermal Camera

Thu, 22 Feb 2018 03:43:36 +0000

My recent SONOFF WiFi Switch experience reminded me of something from high school. I attended an off-site electronics class with my best friend. As teenage boys, we were prone to doing stupid things. One of our favorite games was to see who could handle the highest voltage. Our bench had a variable AC supply that went from 0 to 120 volts. So we would grab the alligator clips while the other person slowly turned the knob up. John once made it to 50 volts. I seem to recall my tolerance around 30 volts. First, DO NOT do this. It was stupid. Second, I think this game is why handling AC makes me so uncomfortable.

Circuit Python adds Python to Microcontrollers

Wed, 14 Feb 2018 14:57:09 +0000

Back in 2013, a Kickstarter ran for a project to put a python interpreter on a microcontroller. At the time I could not see the benefit. Cool project, but I asked myself: “why?” On my last Adafruit order, I received a free Circuit Playground Express. The board comes with CircuitPython pre-installed. After playing with Circuit Python, or CP, I finally “get it.” For Valentine’s Day, I made an animated LED heart for a new love in my life, Circuit Python. Well, love is a bit of a strong word. The past couple of weeks I have been l earning Circuit Python, and I am excited by what it offers.

Hologram.io connects Adafruit FONA

Thu, 08 Feb 2018 03:00:18 +0000

While the buzzword “IoT “is relatively new, there has been a long time “internet of things” in operation. Those devices are called the far less sexy term “M2M” or machine-to-machine. These devices, around since the 90s, contain a microprocessor, some sensors, sometimes electromechanical hardware, and a cellular radio. These M2M devices were (and still are!) the early “Internet of Things.” Thanks to Hologram.io, you can join this new/old trend for free.

DIY Arduino Schematic board and Checklist

Wed, 17 Jan 2018 14:00:18 +0000

One of the last significant steps in a project is designing the custom PCB. This stage means creating a DIY Arduino board that is custom to the application. Two examples of my past projects are BinBoo, a Binary Clock, and Open Vapors, my reflow oven controller. While working on a project for a friend, I got to thinking; it would be nice to have a checklist for circuit elements to include on a DIY Arduino board. In the early days, I forgot to add a filter cap to AREF, for example.

7 Arduino LCD display tips and tricks

Thu, 21 Dec 2017 17:30:03 +0000

When I started working on Open Vapors, I thought the stumbling point would be the PID algorithm or safe AC line control. However, it turned out; I spent a significant amount of time understanding how to print to the Arduino LCD display correctly. If you need an easy to use RGB LCD, check out the Grove LCD from SeeedStudio. They sent me one to check out. The LCD comes with Seeed’s “grove connector system” which can connect to a variety of their Arduino-compatible boards. You can also pick up the Grove Base Shield which adds a variety of Grove connectors to an Arduino Uno. The Grove LCD makes it super easy to connect up a character LCD. It is very plug-and-play.

Arduino Keyboard Matrix Code and Hardware Tutorial

Fri, 15 Dec 2017 14:00:26 +0000

As a kid, I got the book " Upgrading and Repairing PCs." (Now in its 22nd edition.) It was the first book to explain to me the PC architecture. I considered, how were there so few pins on an AT-style keyboard connector when there were 101 keys on the keyboard? That is when I first learned about the keyboard matrix. Intel_P8049_AH_controller The keyboard matrix itself did not amaze me, but instead the idea there was an entirely separate 8-bit microcontroller inside of the keyboard. Early keyboards may have used the P8049AH, which, there is still some stock available to purchase. I was fascinated with the idea an entire computer was necessary to run the keyboard, to use my “real” computer. Why did it take something as complicated as a microcontroller?

Aluminum Polymer Capacitors on EE Journal's Chalk Talk

Mon, 30 Oct 2017 22:38:05 +0000

What are aluminum polymer capacitors? These are a solid type of capacitor that replaces the liquid electrolyte with a solid polymer material. Sometimes you might hear these capacitors called “organic aluminum.” Technically, they are still “electrolytic” capacitors. However, the colloquial term of “aluminum electrolytic” refers to the traditional wet electrolyte-based capacitors. In this video, I meet with Amelia Dalton of EE Journal, and we discuss these capacitor types. Mouser and EE Journal developed the video in joint with KEMET. (Previously I talked on Amelia’s Chalk Talk about SSD Capacitors.)

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Voltage Dividers as Regulators?! | AddOhms #22

Mon, 16 Oct 2017 13:00:15 +0000

Can you use voltage dividers as regulators? What if you add a Zener Diode? In this AddOhms episode, I show what happens when you try to power a complex circuit like an ESP8266 with a voltage divider instead of a regulator. (Spoiler: Get a voltage regulator.) This video tutorial is related to a write up I did recently on Zener Diodes. For questions or comments visit the AddOhms Discussion Forum. Behind the scenes A significant change for this AddOhms Episode is that I moved from Final Cut Pro X to Premiere Pro. I also shot the entire video in 4K, even though the output is 1080p. Animations were still done as 1080p compositions. One snag I ran into, the color corrections I applied in PPro, didn’t seem to get exported. You might notice when the breadboard is on screen, it has a very slight yellow tint to it.

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Op Amp Circuits by Bob Pease

Wed, 27 Sep 2017 17:45:07 +0000

Op amps are one of the most versatile ICs in electronics. A purely analog device, they can be used for amplification, summing, integration, and a whole host of other circuits. AN-31 from Texas Instruments is 32 pages of op amp circuits. (Note: this document was created before TI acquired National Semiconductor.) Even more amazing is that the author is Bob Pease. If you never heard of Mr. Pease, please spend a few minutes right now reading this TI page dedicated to him. His contributions to electronics are nearly immeasurable. (Sadly, he was involved in a car accident after attending the funeral of his equally famous engineering friend, Jim Williams.)

Zener diode makes for a lousy regulator

Wed, 20 Sep 2017 12:57:08 +0000

The Zener diode is often used to create a reference voltage. In tutorials and even college texts, there are mentions of creating a Zener diode based regulator. The idea is that the Zener maintains a known voltage drop. The problem is that current matters. This post looks a quick Zener diode overview and shows what happened when I tried to power a microcontroller using a “Zener diode regulator.” Zener diodes overview Just a brief overview if you are not familiar with Zener diodes. Like typical diodes, Zeners have low forward voltages. Typically you voltages are around 0.7. However, different material sets can offer different forward voltages.

5 Voltage divider circuits that go beyond dividing

Wed, 23 Aug 2017 13:19:15 +0000

Hey Newsletter Readers: Looking for Best Resistor Sorting Method? My Bad! Here are some ideas of what you can do with the humble voltage divider. This elementary circuit has a few inventive uses. To be upfront, one of these uses is NOT as a voltage regulator. If you need a voltage regulated, get a voltage regulator! At some point or another, I’ve built all five of these voltage divider circuits. For me, the voltage level shifter is the most common.

Pi Cap Hands On Review

Wed, 16 Aug 2017 13:05:52 +0000

The Pi Cap adds capacitive touch buttons to your Raspberry Pi. Bare Conductive was kind enough to send me one. I do not have a project in mind right now, so here are my first impressions. What is the Pi Cap? Arduino tends to call daughter cards shields, while the Raspberry Pi community calls them hats. The Pi Cap is a hat. It plugs into the GPIO header of a Raspberry Pi and provides 13 capacitive touch pads. There is a traditional push button, an LED, and a prototyping area. While the Pi Cap does consume all of the GPIO pins, several are broken out near the GPIO header.

Brushless DC Motor Introduction | AddOhms #21

Wed, 26 Jul 2017 13:20:18 +0000

The first part of the tutorial looks inside of a Brushless DC Motor, or, BLDC. Then I show a discrete transistor circuit that can drive one. Of course, you’ll need a Microcontroller like an Arduino to drive it! Lastly, I briefly talk about an ESC. Overall, a BLDC is better than a Brushed DC Motor (talked about those on #20) because: There are no brushes to wear out No sparks when the motor spins You can get way faster RPMs out of a BLDC. Check out the AddOhms #21: Brushless DC (BLDC) Motors. Show notes are available here.

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Top of the P(acq) - Oscilloscope Talk

Mon, 24 Jul 2017 13:58:10 +0000

Supplyframe Hardware has published a video of a talk I gave in July 2017. This talk was at HDDG 22. The focus of my discussion was how an oscilloscope’s trigger circuit works. I built on that and talked about some of the behind-the-scenes stuff of what is going on with a digital oscilloscope. (You can download my HDDG 22 slides here.)

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PWM a 3-pin PC fan with an Arduino

Wed, 05 Jul 2017 13:13:53 +0000

A question came up on IRC regarding how to PWM a 3-pin PC fan with an Arduino using analogWrite(). Controlling the fan was seemingly straightforward. The problem was that the hall effect sensor, or TACH signal, was incredibly noisy. The noise made it impossible to measure the fan’s rotation. Working through the question, I found three issues to tackle: You need to use a PNP transistor Filter capacitors help Create a non-blocking RPM measurement (with millis()) This post addresses all three issues regarding how to PWM a 3-pin PC fan with an Arduino.

Raspberry Pi Startup Script Tutorial

Wed, 28 Jun 2017 13:03:46 +0000

The last couple of weeks I have been making progress and posts on my RetroPie build. I’m putting a Raspberry Pi inside of an actual SNES (well Super Famicom). Part 1 covered the schematic for a Soft Power Controller. In Part 2 I broke down the RPSPC state machine. This 3rd and final post of the series is a Raspberry Pi startup script tutorial. It covers how to make scripts run at startup and shutdown.

Soft Power Controller State Machine

Wed, 21 Jun 2017 13:00:43 +0000

Previously I looked at the hardware needed to build a Raspberry Pi soft power supply. This week I’m looking the state machine for the microcontroller. Why is such a complicated circuit necessary? I am replacing a Super Famicom (SNES) motherboard with the Pi. The trick is, I want to use the original power switch to turn the Pi on and off. This requirement presents a problem. When the switch goes into the “OFF” position, power needs to stay on long enough for the Pi to properly shutdown. So the switch itself can’t provide power to the Pi directly. With minor changes, the code in this state machine could be made to work with push buttons as well. If I add that feature in the future, I’ll update the code on the RPSPC GitHub project.

Raspberry Pi Soft Power Controller - The Circuit

Wed, 03 May 2017 23:18:56 +0000

The RetroPie project enables retro-gaming with a Raspberry Pi. All of the Pi models have enough computing power to emulate the major 8-bit and 16-bit computers of the 80s and 90s. With the Pi 3 I have even been able to play PS1 games with no problem. My current project is to put my Raspberry Pi running RetroPie into an old Super Famicom (SFC), or SNES, case. The catch? I want the original SPST power switch to work. And by work, I mean allow the Raspberry Pi to shutdown properly when the switch goes into the off position. To accomplish this task, I am building a Raspberry Pi soft power controller.

Share projects on one of these 4 platforms

Wed, 26 Apr 2017 13:00:54 +0000

Sharing is the maker community’s foundation. When you share projects with others, you contribute to the community. In the past, you might just post your project on a personal website. Today there are many options to share projects. This weekend I “finished” my reflow oven controller, Open Vapors. Believe it or not, five years ago there were not a bajillion similar projects. In fact, I based my design on the only completely open source project I found. It is a reflow oven controller Arduino shield from Rocket Scream.

Detect short and long button press using millis

Wed, 19 Apr 2017 12:00:48 +0000

To detect a short and long button press using millis can give your project more functionality without adding more buttons. In this line-by-line example, I show how to react to a user pressing a button for a short period (100ms) or a long period (over 500ms). My example changes the blink rate of an LED on short presses. A long button press turns off the LED. In the code, I make use of a struct so that a single variable can be used to track multiple parameters. The benefit of this method is that adding multiple buttons is easy. You could create an array of these tyepdef’d variables.

Best Sorting Resistors Method

Wed, 12 Apr 2017 13:00:51 +0000

When you buy a grab bag of components, you might need to tackle sorting resistors. Here’s how I sorted some bags of random resistor assortments last week. Objectives Then method I use for sorting resistors achieves these objectives: Fewer Bins. It doesn’t take long to create a large matrix of resistor values. My resistor sorting method is relatively compact. Quick to find. When I’m building up a circuit, I don’t want to spend time sorting through a pile. Once I know the value I need, I find a single package and then look for a single color band. Works with 4-band and 5-band resistors. Let me be upfront: I *hate* 5-band resistor color codes. While the 5th ring is supposed to be slightly offset, or wider, or a different type of color; it doesn’t matter. It’s nearly impossible to tell read a 5-band resistor color code when they are in a pile. However, using my method for sorting resistors, it doesn’t matter if I’m looking at a 4-band or 5-band resistor. I can immediately identify the resistor value. Based on #3 alone, you might be wondering what is the fantastic method (and how much will it cost to get it!) Here’s the basics of my method for sorting resistors. (For FREE!)

Arduino Data Logger: Serial Monitor Alternatives

Wed, 05 Apr 2017 13:00:56 +0000

The Arduino serial monitor is usable when you want to watch data from an Arduino. However, it does not have a built-in method for saving the data. Here are some ideas if you want to build an Arduino data logger with or without a PC. Important note on Arduino Data Logger examples With all of these examples, please remember that whenever you open the Arduino’s serial port, the board will reset. So if your log file shows “Initializing SD card…” with a few data lines in between, it is because there is a reset happening.

Sending simple serial commands to an Arduino

Wed, 01 Mar 2017 15:00:16 +0000

Sending simple serial commands to an Arduino is the easiest way to communicate between an Arduino and a computer. The computer could be a PC, a Raspberry Pi, or any device that communicates with serial. By sending and “decoding” a single character it is easy to add a simple debug menu or even serial menu. Plus, it is easy to extend. Single Character vs. Full Words The mistake I see many people make is that they try to send full-text strings as serial commands. For example, to turn on a LED, I have seen (silly) commands like “RED LED ON” or “RED LED OFF.” While you could use something like strcmp(), as I showed on the Multiple MQTT Topics example, that tends to be overkill for most serial commands.

Multiple MQTT Topics with Arduino PubSubClient

Wed, 01 Feb 2017 13:00:22 +0000

In my Arduino MQTT Examples, I kept things simple by only subscribing to a single topic. One of the strengths of MQTT is that a device can subscribe (or publish) to multiple topics. The broker will sort things out. Even though my first example only showed one, it is straight forward to get the Arduino PubSubClient library to subscribe to Multiple MQTT topics. The quick answer is that you need to look at the MQTT response to find out which topic sent the payload.

Why ceramic capacitors change capacitance

Fri, 06 Jan 2017 23:18:03 +0000

It is commonly known that ceramic capacitors change capacitance with applied voltage. What isn’t always as well known is how strong this effect can be and why it occurs. At KEMET we’ve put together a technical video that answers that question. What is Ask An FAE? Ask An FAE is a new video series we launched at my day job, KEMET. An FAE is a field application engineer. These engineers are very common in the electronics industry. Companies like KEMET, where I work, have FAEs who meet with customers to answer technical (and very detailed) questions about how to use their products. In UBM’s Mind of an Engineer survey, FAEs were ranked as one of the top information sources for design engineers.

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Fading LED: analogWrite millis() Example

Wed, 23 Nov 2016 14:34:21 +0000

It’s a well-known fact of engineering: LEDs make everything look better. And that means a Fading LED is even better. Using Arduino’s analogWrite(), fading a LED is just a matter of a loop. If you use delay(), you can’t easily add other actions. What can you do? Well, Fading a LED with millis() is pretty simple. Here’s the code to do it and a quick explanation. //pwm-fade-with-millis.ino // Example Fading LED with analogWrite and millis() // See baldengineer.com/fading-led-analogwrite-millis-example.html for more information // Created by James Lewis const byte pwmLED = 5; // define directions for LED fade #define UP 0 #define DOWN 1 // constants for min and max PWM const int minPWM = 0; const int maxPWM = 255; // State Variable for Fade Direction byte fadeDirection = UP; // Global Fade Value // but be bigger than byte and signed, for rollover int fadeValue = 0; // How smooth to fade? byte fadeIncrement = 5; // millis() timing Variable, just for fading unsigned long previousFadeMillis; // How fast to increment? int fadeInterval = 50; void setup() { // put pwmLED into known state (off) analogWrite(pwmLED, fadeValue); } void doTheFade(unsigned long thisMillis) { // is it time to update yet? // if not, nothing happens if (thisMillis - previousFadeMillis >= fadeInterval) { // yup, it's time! if (fadeDirection == UP) { fadeValue = fadeValue + fadeIncrement; if (fadeValue >= maxPWM) { // At max, limit and change direction fadeValue = maxPWM; fadeDirection = DOWN; } } else { //if we aren't going up, we're going down fadeValue = fadeValue - fadeIncrement; if (fadeValue <= minPWM) { // At min, limit and change direction fadeValue = minPWM; fadeDirection = UP; } } // Only need to update when it changes analogWrite(pwmLED, fadeValue); // reset millis for the next iteration (fade timer only) previousFadeMillis = thisMillis; } } void loop() { // get the current time, for this time around loop // all millis() timer checks will use this time stamp unsigned long currentMillis = millis(); doTheFade(currentMillis); } Global Variables for Fading LED Constants The constant “pwmLED” is the pin that gets faded. (Make that pin supports analogWrite().) The two #define statements, UP and DOWN, are simple states for the LED. They make the code easier to read. The “maxPWM” value is set to 255 for 8-bit AVR boards like the Uno. If you’re using the ESP8266, set this value to 1023. (You can also use the constant “PWMRANGE.”)

Measure PWM Current with a Modified Moving Average

Wed, 28 Sep 2016 13:00:16 +0000

Pulse Width Modulation (PWM) makes it possible to dim lights, control the speed of motors, and (with the help of filters) generate analog reference voltages. When measuring the voltage or current of a PWM signal, there are unique challenges. You can use this tutorial to measure PWM current with a modified moving average (MMA). As I’ve mentioned in a few posts, I’m working on an RGB LED IoT controller. Soon I’ll post some detailed information on that. In the meantime, one choice I made was to include an INA219 current sensor on the LED power supply. For prototyping, I’m using the Adafruit Breakout Board, but my final design uses the same parts integrated into a custom PCB.

Brushed DC Motor Video Tutorial

Sat, 17 Sep 2016 16:36:39 +0000

How a Brushed DC Motor works and how to use them This Addohms Electronics Motor Tutorial goes into the third dimension. Using a 3D model, we show what makes a brushed DC motor, well, a “brushed motor.” (Hint: It’s the brushes!) Then, as usual, we break down two simple ways to control them with a microcontroller like the Arduino. You can use a single BJT Transistor (remember those from #10?), build a discrete H-Bridge to go in both directions, or use a popular H-Bridge chip like the L293D or L298D. (Notice the ‘D’!)

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Social Media Guide for Engineers, a How-To

Wed, 14 Sep 2016 13:48:45 +0000

Bloomicon / Shutterstock.com Engineers are notorious introverts. An untrue generalization is that introverts hate being social. Like all humans, introverts are social creatures. We just prefer only to discuss the topics which are of interest to us. We will listen to anything. This social media guide for engineers explains why and how you can participate in social media, without being social. Let’s address something head-on. Gone are the days of just “here’s what I ate” or “I’m in the bathroom” social posts. Social media channels are mature platforms for communication. Sure, junk still exists. However. You can filter out the signal from the noise when you following my social media guide for engineers.

3D Printer Tips I wish I knew 3 years ago

Wed, 31 Aug 2016 13:00:48 +0000

While I bought my 3D printer a couple of years ago, in March of this year, it only had 75 hours of use. Since March, my counter is over 300 hours. Why? After spending some time doing the right tweaks my printer is printing crazy good. Here are some of my 3D printer tips. Maybe you’re in the market for a printer, use one at school, get access to one through a maker space, or (like me) used to use yours for a desk ornament, these 3D printer tips are likely to help.

5 Common Arduino Programming Mistakes

Wed, 17 Aug 2016 13:39:41 +0000

Whenever someone sends me some code that doesn’t work, there are a few common Arduino programming mistakes that I check. Some of these mistakes I make myself. In most cases my code will compile just fine. Sometimes, these mistakes won’t generate any compiler error. When my Arduino code is acting up, these are the first things I check. Here are my 5 common Arduino programming mistakes, I use to debug non-working code.

Current Flow Direction

Wed, 22 Jun 2016 13:00:15 +0000

A couple of weeks ago I wrote about four current flow direction myths. As a follow up to that popular post, I decided to dedicate this month’s AddOhms electronics tutorial video to Current Flow. In episode #19, I tackle the question of which way does current flow. You might have heard about “conventional flow” and “electron flow.” In conventional flow, we assume that current flows from the positive voltage towards the negative voltage. In digital, the “negative voltage” is usually called ground. However, that’s not how the electrons move nor is it how they carry the charge around a circuit path.

Watch this video on YouTube

Arduino Bootloader, What is it?

Wed, 15 Jun 2016 13:00:14 +0000

Almost all microcontroller (and microprocessor) development systems use some form of a bootloader. Often called firmware, mistakenly, the Arduino bootloader is one example. Since it is a rather popular platform, let’s use it as an example. Let’s talk about what a bootloader does and how it works. When a microcontroller turns on, it only knows how to do one thing. Typically, that one thing is to run an instruction found at a specific memory location. Often this location address 0x0000, but not always. Usually, this memory location will contain a jump instruction to another place in memory, which is the start of the user program. The bootloader, however, exists in a slightly separate memory space from the user program.

KiCad BOM: Don't Bomb your BOM!

Wed, 08 Jun 2016 13:00:27 +0000

A KiCad BOM is a list of all the parts your design is using. The term BOM, or bill-of-materials, is standard for supply chain management and does not just apply to electronics. KiCad’s eeschema has a BOM export feature. Unfortunately as of Version 4.0, this feature is still somewhat lacking. Given the limitations, here are some tips to take your KiCad BOM from Schematic to Mouser. Spending a few extra minutes while capturing (drawing) your schematic thinking about your KiCad BOM can save you a ton of time later on. Moreover, as you build up a database of parts, these extra minutes turn into seconds. Here are a couple of ways to describe your parts, especially passive components, better while drawing schematics in KiCad.

They're JUST Capacitors?

Wed, 08 Jun 2016 00:20:22 +0000

I was invited to speak at the 11th Hardware Developers Didactic Galactic group at the Supplyframe office in San Francisco. I talked about the misconception that capacitors are a simple device. Chris Gammell recorded the discussion and posted it via PHY Media. This video is about 50 minutes. In this talk, I break down a few things to know about Ceramic, Aluminum, Tantalum, and Supercapacitors. You can see the full video via PHY Media’s YouTube Channel: They’re JUST Capacitors. For links and the slides, check out this post.

Watch this video on YouTube

6 Electronic Safety Tips I learned while Mountain Climbing

Wed, 18 May 2016 13:00:55 +0000

Electronic safety tips from mountain climbing? Yes! After spending two weeks in Europe for work, I had the chance to spend a weekend with friends in Germany. We hiked up Kampenwand in Bavaria. While working my way through the snow and rocks, I realized mountain climbing safety tips were the same as electronic safety tips. Really! Here’s how. Grabbing a soldering iron and throwing polarized components around a circuit board is something I often do. So often, I don’t even realize I’m using some of these electronic safety tips. However, a new activity gives you a chance to exercise the safety portion of your brain. Especially when there are no guard rails.

Four Current Flow Myths Addressed

Wed, 27 Apr 2016 14:00:29 +0000

Current flow (direction) is the topic I’m planning for my next AddOhms tutorial. While preparing the script, I started to realize there are some myths or misunderstandings about electricity and current flow. Ben Franklin Father of Current Flow Everyone probably knows Ben Franklin. He discovered electricity, of course! Yet, he didn’t. Franklin was the first to prove that lightning was composed of electricity with his famous kite experiment. He was also the first to provide electricity’s well-known labels: positive and negative. And somewhere in there Franklin became famous for “inventing” conventional current flow.

Switching Voltage Regulator Tutorial

Wed, 13 Apr 2016 13:00:04 +0000

A switching voltage regulator is one of my favorite circuits. In school, they were the first circuits I built where I understood how transistors worked. In fact, they were the first circuit I saw an inductor being useful! Switching regulators are incredibly efficient when designed properly. Of course, this detail about design is important. They are not as simple as a linear regulator, which is basically an IC and two caps.

How to Turn Your Arduino Prototype Into a Manufacturable Product

Wed, 30 Mar 2016 14:00:33 +0000

This week’s post is from my friend John Teel. I asked him to help answer a common question I receive: " How do you make an Arduino project into a product?" His experience as an electronics design engineer and serial entrepreneur is ideal to talk about going from prototype to product. He has developed tech products that sell in the millions of units. John now helps entrepreneurs, startups, makers, and small companies bring new electronic products to market. Check out the company he founded, Predictable Designs, and his free cheat sheet - 18 Steps to Market for Your New Electronic Product after reading his excellent post below. Dreaming of bringing a new hardware product to market? Perhaps you think your product will make the world a better place, or maybe you just dream of making millions of dollars.

Energy Density of 9V battery vs. AA batteries

Wed, 23 Mar 2016 13:00:53 +0000

Previously I wrote up why the 9V battery sucks. As I thought more about that post, I realized, I never explained how much energy is in a 9 V battery versus say a couple of AA batteries. For this post, I am going to break down the energy stored in a 9 V battery, the small rectangular kind and compare it to what you get with 6 AA batteries. Yes, it takes up a little more space, but you might be surprised by the difference.

Logic Analyzer Tutorial and Introduction

Wed, 09 Mar 2016 16:00:17 +0000

A DMM, or multimeter, is the go-to instrument for debugging most circuits. You probably already have at least one DMM on your bench for this reason. Me? I have three. But that’s a different story. Let’s talk about a Logic Analyzer. Digital signals represent two states: on (usually “1”) and off (usually “0”). A multimeter (DMM) may be of limited value for these signals. When using the DC voltage measurement, you can see “something” is happening, but not exactly what that “something” is. For example on a PWM pin, you’ll see the RMS Voltage change as you modify the duty cycle. However, you can not see if the signal is “ringing” when turning on and off.

Arduino to ESP8266, 5 reasons to switch

Wed, 02 Mar 2016 16:00:04 +0000

A couple of weeks ago I posted four things to know about the ESP8266 before using one. The biggest surprise from that post is people seem to think I do not like the ESP8266! This idea is not the case; the ESP8266 is awesome. I like them so much that my Adafruit Feather HUZZAH with ESP8266 has become my go-to Arduino board. Wait what? James uses something other than Arduino? Yes, I do! I have many different boards and have used most of them for one task or another.

MQTT Tutorial for Raspberry Pi, Arduino, and ESP8266

Wed, 24 Feb 2016 16:00:45 +0000

This week’s MQTT Tutorial connects a Raspberry Pi, ESP8266 (or Arduino), and a PC together. Remember last week’s post provided an overview of message brokers and MQTT. We learned that MQTT is a hub and spoke protocol for sending messages between IoT devices. Clients can subscribe or publish messages to a central server, called a broker. Now it’s time to connect our IoT devices together! For this MQTT tutorial, I have three main elements: • My Computer, which will act as the broker. • Raspberry Pi running Python • ESP8266 controlling an LED

MQTT Introduction and Tutorial Part One

Wed, 17 Feb 2016 16:00:25 +0000

MQTT is an easy way for Internet of Things (IoT) devices to communicate with each other. This light-weight protocol can be used with a simple 8-bit Arduino to a Raspberry Pi to a multi-core PC to Amazon Web Services. It is that versatile. This MQTT Tutorial is broken into two parts. Part one is an MQTT Introduction. You’ll understand how publish/subscribe message brokering works. Next week, Part two will be a tutorial on using MQTT to communicate between a PC, Raspberry Pi, and ESP8266.

Raspberry Pi GUI Tutorial

Wed, 03 Feb 2016 17:58:53 +0000

My favorite Raspberry Pi add-on is the PiTFT from Adafruit. With it, you easily get a Raspberry Pi GUI interface and touch screen. The PiTFT software install is just a few things and it is good to go. Adafruit PiTFT - Click for more info This screen is what I needed for my IoT project. The Pi+Screen will act as the primary controller for all of my things. The problem is I didn’t know much about writing GUI applications in Linux. So what could I do to create a Raspberry Pi GUI?

Use Arduino millis() with buttons to delay events

Wed, 27 Jan 2016 16:00:16 +0000

One of the common questions related to using the millis() function in Arduino, is around timed events. After an event occurs, you want the code to wait for some time before doing the next step. But you don’t want to stop the program with delay(). In this example, we will use millis() to wait a few seconds after a pushbutton press to turn on an LED. Then a few seconds later, we will turn it off. All without using delay().

Four ESP8266 Gotchas and a tip for a first time users

Wed, 02 Dec 2015 16:00:13 +0000

Adding WiFi to any project can be difficult. There are a few off the shelf options that make it easier. One option is the official Arduino WiFi shield. This full-featured shield uses its integrated microcontroller to handle the WiFi protocol, security, and the TCP/IP stack for you. From “plug it in and go” perspective, this is an awesome option for Arduino-based projects. Plenty of example code supports the nicely designed hardware. The main downside to some people is the price.

Build a proper R-2R DAC

Fri, 06 Nov 2015 16:10:58 +0000

Creating real analog outputs from a digital pin is possible when you use an R-2R DAC. What is a DAC? The letters stand for D igital to A nalog C onverter. This simple DAC is built using resistor. The principle works on voltage dividers. By enabling different combinations of resistors, it is possible to get various voltage levels. Obviously, such a simple design will have some trade-offs.

Proper Larson Scanner with Software PWM (Repost)

Wed, 21 Oct 2015 16:00:03 +0000

Last week I had a detailed Arduino tutorial on software pulse width modulation using millis() and micros(). Why? Because I wanted to create a Proper Larson Scanner, with persistence and at least 8 LEDs. KITT larson scanner example Even though it is a popular project for the Arduino Uno, most Larson scanner tutorials, like my first one, have a few flaws. First, there is no persistence, or tail, to the LED as it moves back and forth. Persistence could be solved by using pulse-width-modulation. The Uno and other 328p-based micros only have 6 Pulse Width Modulation (PWM) pins. And let’s be honest, every project is made better by adding more LEDs. :)

Arduino Software PWM with millis()

Wed, 07 Oct 2015 13:00:04 +0000

The Arduino Uno has six pins dedicated to Pulse Width Modulation (PWM). PWM is great for analog-like control for the speed of motors or LED fading. But what if you want to control more than 6 devices? Or what if you’re using the PWM pins to control servo motors, but still want to fade an LED on a 7th pin? One option is to change boards and processors. For example, you could move up to the Arduino Mega 2560. That means a bigger board and more cost.

How Arduino digitalWrite Works – and why AVR is Faster

Mon, 05 Oct 2015 13:00:18 +0000

Previously I looked at the speed difference between digitalWrite and direct port manipulation. It was a chance to check out a Saleae Logic Analyzer. Andrew at !Crash-Bang Prototyping took the analysis a step further. He broke down what is going on inside of digitalWrite(). This study is useful. When you’re ready to move beyond the Arduino IDE or the core functions, you can decide if you need your own version of digitalWrite().

My Modular Soldering Station for the Space Limited

Wed, 30 Sep 2015 13:00:06 +0000

Solder is the glue of electronic circuits. In addition to a permanent mechanical connection, solder provides an electrical connection. Not too much unlike glue solder combines two separate metal pieces with a bonding material. In this case, the bonding material is a metal or allow with a relatively low melting point. When soldering together a circuit, the quality of the solder joint is crucial. Most people probably recognize the need for a high-quality soldering iron, like the FX-888D from Hakko, but about the other tools?

Get electronics help with the right question

Wed, 03 Jun 2015 14:00:03 +0000

4 keys to getting electronics help for your project When describing a person, do you ever use the phrase “their strength is their weakness?” That’s how I feel about Internet forums. The strength of forums is the collective knowledge of like-minded people, some with more experience than others. Sadly, that is also the weakness of Internet forums… Whether it is a topic-specific site like the EEVBlog Forum or an almost anything site like Reddit the strength/weakness holds true.

What's the difference between Series and Parallel Circuits?

Wed, 27 May 2015 14:00:28 +0000

Tutorial on schematics basics The funny thing about schematics is that they are much easier to draw than they are to read. There are many common circuits. When an experienced engineer looks at them, it’s like a second language. When someone less experienced looks at them, it looks like random lines and symbols thrown together at the last-minute. (Or maybe that’s just the schematics *I* draw.) Other than reading Schematic Symbols themselves, one of the basic skill necessary to read a schematic is recognizing series and parallel circuits.

An example of when comments would have helped

Tue, 07 Oct 2014 14:00:05 +0000

What was one of the first things you were taught, when learning to program? “Comment Your Code!” And of course, like all programming students, you ignored that advice. Or, if you are like me, you made vague comments as the lines of “variable called var.” Tonight I opened up some code I haven’t touched in two years. Code that when I wrote it, made perfect sense to me… at the time.

Using Adobe Illustrator to Create A Sine Wave

Fri, 15 Nov 2013 11:33:52 +0000

When working on the AddOhms video on the difference between AC and DC, I needed a vector diagram with a sine wave. Using Adobe Illustrator, I tried with a Bézier tool, but it didn’t look quite right. Here’s two methods I found to create a better line sine. The Quick (but not Accurate) This method will give you something that looks sort of like a sine wave, but isn’t actually a sine wave. So if you just need a quick wavy line, this is pretty simple.

Tutorials

Thu, 20 Dec 2012 23:36:19 +0000

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How to Fix: Arduino is damaged and can't be opened

Fri, 23 Nov 2012 03:06:52 +0000

Open source software that isn’t signed by an identified developer can cause headaches upgrading it on OSX. While working with the Arduino Due the first time, I downloaded 1.5 Beta of the Arduino IDE and ran into this error: “Arduino is damaged and can’t be opened. You should move it to the Trash. Here’s why you see the “… is damaged and can’t be opened” dialog and how to fix it.