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’!)

Tutorial Contents

The video starts with a couple of (mixed) motor examples. Do you know what a “stator” or “rotor” is? If not, that’s okay because that’s one of the first things we explain. After that, we add part like the commutator and brushes to make the Brushed DC Motor. After that is control with a transistor and an explosive reason you need a protection diode. 🙂 Then we show how an H-Bridge Works. Lastly, the advantages and disadvantages of this motor type.

You can see the full Brushed DC Motor Tutorial on YouTube or on the AddOhms page.

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Circuit Trading Cards Review

Arachnid Labs makes learning circuit basics simple

One of my early hobbies as a kid was collecting baseball cards. At every card show, I was on the lookout for the  1989 Ken Griffey Jr Rookie card, #1, from Topps. My collecting craze lasted until the baseball strike in 1994. Then I lost interest in professional baseball and its collectibles.

You’re asking, what does this have to do with electronics? Well, the Circuit Trading Cards from Arachnid Labs reminds me of the days I spent trading baseball cards. Instead of memorizing RBIs and Homerun counts, these circuit patterns trading cards teach you circuit basics.

The card stock used is of high quality, and each unique card has a durable feel. One side is the Arachnid Labs logo while the other is what I call the “information side.” The information side is one of three colors: Yellow (Analog), Blue (Digital), and Green (Power).

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100kGarages: CNC Router Bits Demystified

Early on in planning the design for the Quadrotor, we knew that eventually some of the metal parts would need to be milled.  Having very little milling experience, other than a couple of basic-use classes at TechShop, I had no milling experience.  When it came time to start buying router bits for the ShopBot and Tormach CNC routers, I didn’t know what kind of bits were necessary.

Understanding End Mills

Greg over at 100kGarages put together a primer titled CNC Router Bits Demystified, which does a great job of explaining the basics of an End Mill, Ball Nose, Downcut, Upcut etc.

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6 things I learned about KiCad at KiCon 2019

Re-cap of the stuff I found interesting at the first conference for hardware developers

In April 2019, hardware hackers, hobbyist, and engineers joined together for the first KiCon. A couple of people asked me, “why is there a conference for KiCad?” Some questioned if KiCad was significant enough software to warrant a conference. That question is valid. But KiCon is larger than the KiCad software. Even in its first iteration, KiCon evolved more into a meeting for people building electronics hardware from small scale hobbyist to professionally designed systems, than just a conference on a single piece of software. Some might call it a maker conference. I call it a hardware developer conference. The key that tied everyone together is the open source software behind our printed circuit boards.

Twenty-five different talks covered basic KiCad usage, automating tasks, PCB layout techniques, and projects designed in KiCad. Wayne Stambaugh ended the first day with a State-of-KiCad discussion. He introduced the feature list for KiCad 6. Additionally, he announced four new lead developers and that he would be working on KiCad full time. That news means it is likely KiCad 6 will be here faster than the usual two-year release cycle.

In addition to the talks, there were several workshops and panel discussions. The workshops included a getting started with KiCad lead by Shawn Hymel [link]. That one was cool to keep an eye on because people were designing their first PCB, milling it, and then soldering parts to make the boards blink. In another workshop, Anool Mahidharia provided a hands-on guided introduction to FreeCAD. It is a parametric mechnical cad tool. The panels featuerd PCB manufactureres, workflow discussions, and the KiCad development team.

Outside of the planned classes and activities, I finally shook hands with friends whom I only knew through social media. Even though we are all electronics enthusiast or professional engineers, it is rare we end up at the same place at the same time. See what I mean about KiCad connecting liked minded people together?

With so much going on, I realized I couldn’t cover everything. Instead, this post’s focus is the tidbits I learned at the conference and stuck with me after a little bit of time passed. Here are the six things I learned at KiCon 2019.

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Don’t be afraid of learning a new tool

Behind-The-Scenes of AddOhms #14

After moving from learning a new tool to mastery, the resistance for me to switch becomes very high. This can apply to hardware tools like a drill, saw or CNC milling machine. It can also apply to software tools like EAGLE, Programming Languages or video editing software. In AddOhms #14, I gave an overview of the VirtualBench from National Instruments which I’ve covered on this blog as a hands-on, written review and video review.

learn a new tool

Photo courtesy of smuay/

For this AddOhms Behind-The-Scenes look, I talk about my experience with changing my tool set, the most critical tool in fact, I use for creating AddOhms Videos. If you’ve ever wondered how I do those hand animations, keep reading for the deepest look yet into my workflow.

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The hidden Arduino Macro F() fixes random lock ups

It’s 3am but you are not going to bed until you squash this last bug. You sprinkle Serial.print() statements everywhere you can think of, and then that’s when all hell breaks loose:  Your code randomly locks up, the LEDs go crazy, and you’ve had it. What’s going on?  You’ve run out of RAM!

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5 Unexpected Brands at Maker Faire 2018

These companies are not who I think of when I think "maker."

Maker Faire, like any festival, is a combination of passion products, startups, and larger companies generating awareness. As I walked around, I noticed many logos and brands. An obvious one to see is Make Magazine. Another I saw that made sense is Digi-Key’s They had a strong showing, along with the Arduino booth. But that one is expected since so many projects, not just electronics, have an Arduino in them. That said, there were five brands that I did not expect to see at Maker Faire (and most had something interesting to show.)

(Please note, no mentions came from paid placements. I am genuinely interested in their presence at the show.)

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Is Graphene Unobtanium?

(“Graphen” by AlexanderAlUS – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons)

Every day a new application involving the seemingly miraculous material Graphene is announced. For example, being in the capacitor industry, I am asked often if my employer uses it. Before answering the question, I usually have to explain what Graphene is and the challenges in producing it.

The lack of supply and limited (real) commercial applications leads me to think of it as Unobtanium… at least, for the near future.

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Send MQTT over cellular to an IoT Dashboard

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, you can join this new/old trend for free.

I decided it was time to up my IoT game with a GPRS, or 2G, data radio. In this post, I show the hardware I am using to create a 2G-based GPS tracker. It includes a Teensy 3.2 (Arduino) connected to a SIM808 Module (FONA) using a Developer SIM. It transmits GPS coordinates to an Dashboard, which displays them on a map.

This post is not going to be a tidy tutorial. Instead, it is all the steps (and notes) I went through. I will cover:

  1. Hardware pieces I am using
  2. How to verify SIM808 (FONA) module is connected through Hologram via Serial Commands
  3. How to send HTTP/POST requests (including SSL) with the SIM808 (FONA)
  4. My (brute force) changes to the Adafruit FONA Library
  5. Code for sending MQTT payload (GPS Coords) to a dashboard

When done, you will be able to build something like a battery powered GPS Tracker, that updates over cellular. If you are in a rush, grab all the code from the FONA GPS Tracker Github Project.

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2016 Great Year for Enginerds

Top Tutorials from

While many want to call 2016 the worst year ever, I feel that is an entirely undeserved title. It certainly could have been a better year, but it wasn’t the worst that I can remember. For the engineering community, both professional and hobbyist, it seems to have been a fantastic year. My gauge for this feeling is the activity on In 2016, I saw almost half a million sessions contributing over 1.2 million page views. (That’s 98% more people looking at 313% more tutorials compared to 2015.)

Here’s a breakdown of the most visited pages (tutorials) on the site.

Overall Top 5 Tutorials for 2016

First up is a simple list with the most views, across all content.

  1. MQTT Tutorial for Raspberry Pi, Arduino, and ESP8266
  2. Raspberry Pi GUI Tutorial
  3. millis() Tutorial: Arduino Multitasking
  4. Arduino, how do you reset mills()?
  5. Top 4 transistors for your kit

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Test Equipment Alternatives (Suggested By You!)

Your ideas for test equipment alternatives

A couple of weeks ago, I asked my subscribers for their favorite test equipment alternatives. The reason I asked, was because I recently picked up a Mooshimeter. It is a modern take on the multimeter. However, I will cover that in more detail soon.

While I am fortunate that my bench has the usual equipment like an adjustable power supply, oscilloscope, multimeter, and function generator, I know that not everyone else does. I also had to think back to before I had this equipment, what did I use to troubleshoot my circuits.

Sometimes when working on a project, whether hobby or professional, you just don’t have the tools you need on hand. Or worse, you cannot afford it. So here are some of the responses you all sent me.

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Which Arduino Starter Kit is the Best?

Need an electronics kit? Check out these 4 options.

The other day my friend called me up. He told me how much he missed building circuits and wanted to start again with the Arduino.

So he asked me “which Arduino starter kit is the best to buy?” At which point, I drew a long breath. Easy question, not always an easy answer.

Picking out an electronics kit depends on a number of factors. You should consider:

  1. Your budget
  2. What you already have
  3. What you want to do

#1 and #2 are probably pretty easy to figure out. For many beginners, it’s “not much” and “nothing.” When you don’t know #3, what you want to do, then it gets trickier. Coming back to my friend, what did I do? Well, I went out and bought each one of the kits in this post. I put myself in his shoes and maybe these are your shoes as well.

Assuming you have about $100 to spend, have no components on-hand now and just want to “get started” consider one of these 4 Arduino starter kits.

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Debug SONOFF AC Relay with a Thermal Camera

Find the problem without a live measurement

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.

While I am not an electrician, I do know the basics about wiring mains AC circuits. So when one of my studio lights needed a new switch, I was okay to replace it. Mains AC does not scare me when it is off. I did not have a mechanical switch available. Instead, I opted for a SONOFF WiFi Switch. I did not intend to connect WiFi, at least not yet. I just wanted to control the light with the manual push button.

The clever solution seemed to be clever, at least for a few minutes. Suddenly the light turned off. I thought maybe there was a timeout for the manual button. Annoying, but workable. The lamp remained off for about another 2 minutes when I started to smell that unmistakeable burning plastic odor. Touching the case of the SONOFF identified the culprit immediately.

Great. So I have an AC mains switch that isn’t working, but I do not want to go poking my multimeter into it. What do I do?

Turns out, that SONOFF module was defective. I wanted to debug it, but I did not want to measure anything while connected to AC. Here’s how I used a thermal camera to debug my SONOFF.

What is a SONOFF?

SONOFF Board Backside 1600px

See the ESP8266 and Antenna?

The SONOFF WiFi switch is an inexpensive AC relay. Internally it has an ESP12 chip, which became popular with the ESP8266. There is even an unpopulatd serial header which can be used to reflash the firmware. Among hackers, these modules are a popular way to get an AC relay that is easily programmed.

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PCB Checklist – What to check before you submit

Recently I’ve been expanding my retro game collection to include game cartridges imported from Japan. The problem is that I don’t have Japanese game systems (yet). So I’m creating an open source adapter to convert Famicom carts to the NES. Before I submit the PCB to OSH Park, I’m going to run through this PCB Checklist to make sure I don’t forget something silly.

This PCB checklist is something I’ve built over my years of creating boards. If you’ve got tips from your own list, don’t forget to leave a comment letting us know.

PCB Production Checklist

The concepts on this list will apply to almost any PCB software. The tips I give relate to EAGLE, since that is what I use most often. Feel free to comment to add tips for other design software like or KiCad.

Keep reading to see the list.

Make sure you also check out the comments, some really great suggestions there too!

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IoT: Intelligent Outsourcing

How to delegate when producing an IoT product

Whether you are developing a WiFi-enabled coffee maker, a sensor to detect rainfall, or a livestock tracking drone, an IoT device will follow the same product development cycle.

IoT Design Flow

A common mistake that engineers will make is trying to own the development at each stage, at least up until “deliver.” Who can blame us? The idea of delegating any part of our new product introduction can be daunting. Delegating, or outsourcing can be a powerful tool. It allows you to focus on the elements of your process that only you can do. Let others handle the rest. If your core contribution is the machine learning algorithm, then focus your effort there. Spending time designing the enclosure, or negotiating with suppliers, or even laying out the printed circuit board is a waste. Let the people who excel in each of those areas apply their expertise to your product.

Production, or making, is the prominent point for outsourcing. It is common to work with a contract manufacturer to build your product. Some offer complete services that allow them to source your components, produce the product, package it, and drop ship it to your customer. This next statement might sound recursive, but consider outsourcing the step of finding someone to outsource manufacturing.

Let’s look at the Idea, Design, and Source stages for a typical IoT device. At each of these steps, I give some pointers to help identify what you should focus on and what you can delegate to a third-party, as well as, introduce you to a partner to consider.

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Getting PCBs from KiCad to X-Carve

Milling printed circuit boards with open source tools from start to finish.

The last time I looked at using an X-Carve for Printed Circuit Boards (PCBs), I created a demo board with EAGLE. Since then, I have learned more about using KiCad, the open source electronics CAD suite. While not a step-by-step tutorial, here is my rough KiCad to X-Carve PCB workflow. These are just the high-level steps, the tools necessary, and the settings I’ve discovered for each—so far.

Eventually, I will make this a more detailed KiCad to X-Carve PCB tutorial, so make sure you subscribe to my RSS feed for updates.

Here’s the Basic Steps:

  1. KiCad: Draw Board
  2. KiCad: Plot Gerbers
  3. KiCad: Generate Drills
  4. pcb2gcode: Generate G-code
  5. Text Editor: Clean Up G-code Files
  6. Camotics: Simulate G-code
  7. ChiliPeppr: Send G-code and control X-Carve
  8. X-Carve: Make the boards!

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