Electronics Basics on Bald Engineer

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.

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.

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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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?

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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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.

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.

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.

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!)

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.

AddOhms #15: Pull-Up Resistors (and buttons)

Mon, 10 Aug 2015 13:00:05 +0000

The latest AddOhms looks at why you need a pull-up resistor when using push-buttons. This video goes into what happens when you leave a pin floating, what a floating pin means, and how the pull-up works. You can get more information about the video on the AddOhms Episode page. Pull-Up Resistors can be a difficult topic to understand. That’s why I made this video. This tutorial is the 2nd time I’ve made a video on pull-ups. Despite being a single resistor, it can be a difficult topic for new hardware designers to understand. The pull-up video was the first video tutorial I ever made. In fact, the YouTube version uses YouTube’s “stabilization” algorithm, which gives the video a very warped feel.

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Which Arduino Starter Kit is the Best?

Wed, 01 Jul 2015 13:00:33 +0000

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: Your budget What you already have 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.

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.

Cutting Perfect Breadboard Jumper Wires

Fri, 01 May 2015 14:00:22 +0000

Learning to a breadboard is critical when adding electronics to a project. A skill often overlooked is how to use breadboard jumper wires correctly. For example, when I breadboard a circuit I only use Red, Green, or Blue for positive voltages and Black for ground. Other colors, it depends on the functions of the wire. The idea is to keep it clear when I look at the board, what each wire is doing.

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Five ways to make a schematic (quickly)

Wed, 29 Apr 2015 14:00:37 +0000

Engineers make a schematic to explain their circuits. One time I was looking for a non-tourist pub in Japan. I asked someone for help. She said, “I’m sorry, but I do not speak good English. I will bring my friend, and she will draw you a map.” (Exact quote!) The map her friend drew, gave directions to a bar with a “Neon Yellow Sing.” She meant “sign.”

Can a 1µF decoupling capacitor be too much?

Wed, 01 Apr 2015 14:06:12 +0000

To save time, breadboard pins or just lack of knowledge people try to skip adding even one decoupling capacitor to a circuit. Either on IRC or in Forums you can almost always see it coming: “randomly, my circuit stops working” And then, “what do you mean a decoupling capacitor?” question. While working on breadboard Arduino, I came across some unexpected measurements. Initially, the only capacitors on the breadboard were the two 22pF from crystal to ground and the capacitor connected to RESET for Auto-RESET.

AddOhms Electronics Tutorials DVD Now Available

Wed, 25 Feb 2015 15:12:56 +0000

When I was in elementary school, I remember Ms. Coker telling us we needed to memorize our multiplication tables because we wouldn’t always have a calculator. Years later in college I was told, “learn to use the library, it’s not like you can carry the internet in your pocket.” Buy On Tindie Seems strange that I always carry 3 devices on me that do both. Today a generation of people are growing up with the mass of all human knowledge available to them from birth. No formal education is necessary. And the only need is a modern device with WiFi.

6 Simple Mistakes Electronics Beginners Make

Mon, 30 Jun 2014 14:00:47 +0000

Sometimes the hardest lessons are the ones you have to learn multiple times. When getting started with Electronics circuits, there’s a handful of things that can ruin a day (or experiment.) Here are 6 mistakes I made when I got started, and mistakes I see in the beginner classes I teach. In fairness #6 isn’t one I did starting out, because Fritzing wasn’t around. However, it took me a while to learn the value of providing a schematic, even a simple sketched out block diagram.

The 4 best transistors to keep in your parts kit

Mon, 21 Apr 2014 15:00:38 +0000

When your project needs a transistor, there are tons of choices. Which makes answering the question “Which transistor should I use or buy?” a daunting task. Fear not, before wading through spec sheet after spec sheet, consider one of these four general purpose transistors. Every electronics enginerd’s toolbox should have a few of each. Transistors are one of the most versatile discrete components in electronics. In digital circuits, they switch on and off while in analog circuits they are used to amplify signals. For most projects, they are used to turn on a load that would kill the I/O pin of a microcontroller or microprocessor. For most circuits either a BJT or MOSFET can be used, depending on the load current you need to switch.

9V Batteries Suck -- And why you shouldn't use them.

Fri, 14 Feb 2014 12:00:37 +0000

Smoke detectors beep when their backup battery dies, which always seems to occur in the middle of the night (at least for me.) These backup batteries are usually a small rectangular 9V. They have become popular choices for electronics projects. If you need your Arduino project to last longer than a day, this isn’t the battery you want to use. Here’s why. What is a 9V Battery The 9v battery comes in a standard package about 25mm wide, 16mm tall, and 47mm long. On top there are standard snap-style connectors. The design of these connectors prevents you from attaching the battery backwards.

AddOhms #8: LEDs and Current Limiting Resistors

Mon, 10 Feb 2014 12:00:49 +0000

The idea for AddOhms #8 has been around for quite some time. I’m always trying to find ways to explain why current limiting resistors are necessary. So while working in the shop one day, I decided to play with some LEDs and a bench-power supply. Then I decided to record what happens.

Unlike Speed Limits, Ohm's Law isn't a Suggestion

Tue, 31 Dec 2013 12:00:51 +0000

Getting started with electronics always involves a discussion of Ohm’s Law. What is this mysterious sounding law and how can you use it when building electronic projects? One the main uses for Ohm’s Law in your projects is to calculate the resistor value needed for a LED. This article takes a look at what Ohm’s Law is and how to use it with LEDs. Overview Ohm’s Law is really a mathematical rule based on two points. In electronics those two points have a voltage across them (aka potential difference). The amount of current that flows from one point to the other, is going to depend on the resistance between those points. So Ohm’s law says that the Resistance of a device is equal to the Voltage Across it divided by the Current that Flows through it. The formula looks like this:

Electronics: Introduction to Breadboards

Wed, 18 Dec 2013 23:32:05 +0000

Soldering every circuit you build probably isn’t practical. At some point you are probably going to want to use some type of temporary method to connect different components together. One of the popular methods is using a breadboard. This simple (and cool) looking device only needs a few instructions before you can begin Layout of a Breadboard There are various colors, shapes, and sizes that breadboards come in. However, they all generally look about the same and have the same basic functionality. The board shown in Picture 1 is a pretty common “medium” sized breadboard.

AddOhms #6: Analog and Digital

Wed, 13 Nov 2013 12:52:09 +0000

It isn’t always clear what is meant by calling a device or a signal “analog” and “digital”. This AddOhms tutorial explains the difference between analog and digital by using an analogy to clocks. Old-school clocks with hands are a great example of “analog” while alarm clocks with digits as their display are an excellent example of “digital”.

Understand the difference between DC and AC

Wed, 25 Sep 2013 14:10:17 +0000

The fifth episode of AddOhms tackled the difference between AC and DC. One of the things I wanted to stress in this tutorial is that even though the acronyms stand for “current”, they get used to describe voltages as well. Which, after a video on the difference between voltage and current, seemed like something that needed to be stated.

Voltage Regulator Tutorial and Basics

Sat, 06 Oct 2012 20:41:30 +0000

Regulator Types Fundamentally there are two types of voltage regulators: linear and switching. The names come from how they operate and how they achieve voltage regulation. Linear regulators tend to be a little cheaper to implement, but they aren’t as efficient as their more complex switching variants. There are also some “cheap and dirty” methods that some designs use. Below is a brief description and example of each. Linear A simple way to think of a linear regulator is to think of it as an active series resistor. It will vary its effective resistance so that the output voltage remains the same. The upside to such a design is that it is cheap, simple to implement, and provides a relatively clean output. The downside is that the regulator dissipates a relatively large amount of power.

Tutorial that goes over the basics of different regulators types

Sat, 06 Oct 2012 09:13:19 +0000

Digital ICs like microcontrollers, memory, and shift registers need a stable voltage source to make sure they work as expected. Most circuits are designed with a voltage regulator to accomplish this stability. In theory voltage regulators will vary their output to stay at a set voltage, regardless of how much current the load is drawing. As a load draws a little bit more current, the supply voltage will begin to sag. Conversely when the load is reduced the voltage may rise a little bit. Regulators work to eliminate, well minimize, this change.

Arduino Internal Pull-Up Resistor Tutorial

Fri, 30 Dec 2011 07:31:32 +0000

When hooking up switches or buttons to an Arduino I/O pin, sometimes the results might appear completely random. Sometimes it will appear as though there is a delay from when the button is pressed until the state of the pin actually changes. Other times the pin’s value will seem to randomly fluctuate from HIGH to LOW. Even more maddening might be as your finger gets closer to the switch, the pin’s state changes! The fix to these problems is simple: use the Arduino Internal Pull-up Resistor. Here’s how they can fix this problem and how you can use them with an Arduino board.

LED Tutorial - Learn the basics

Wed, 21 Dec 2011 03:13:39 +0000

Nearly every consumer device makes use of the Light Emitting Diode (LED). This highly versatile device offers an easy way to add an indicator to any project while drawing a relatively small amount of current. Once their operation is understood, adding them to any project is a simple task. This tutorial is a simplified explanation of how a LED works and how to select a current limiting resistor. The LED tutorial here is enough to use LEDs in a project but is not intended to be a thorough explanation.

Video Tutorial: Buttons and Pull-Ups

Mon, 19 Dec 2011 05:20:26 +0000

This is a 4-minute video version of the Arduino Pull-Up Tutorial: