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.

Electron flow is the description of how electrons carry a charge. Which is the negative voltage towards the positive? This confusion is a result of Ben Franklin mistakingly identifying how electrons moved so many years ago. Yet, we have kept the “positive” and “negative” labels as they are today.

The key though is that it doesn’t matter which method you use to analyze a circuit. Electrons move in a closed path. So whether they travel from positive to negative or from negative to positive, doesn’t matter!

AddOhms #19: Current Flow Direction

Check out the full AddOhms Electronics Video Tutorial on Which Way Does Current Flow on the AddOhms YouTube Channel.

Capacitor lifetime depends on the materials capacitor lifetime

Although not all applications are safety critical or mission critical, reliability is still a vital consideration for many electronic products. Making informed choices at the part selection stage can help ensure the product will perform correctly over its intended lifetime.

When choosing capacitors, properties such as volumetric efficiency, frequency stability, temperature rating or equivalent series resistance are often the primary factors that govern technology choice. In these cases, understanding factors affecting lifetime can help engineers make sure the product will deliver the required reliability.

On the other hand, a long operational life may be an essential requirement of the end product.

Continue Reading the full article, “Capacitor reliability can be improved with the right materials,” on Electronics Weekly.

Date:September 28, 2015
Appearance:Capacitor reliability can be improved with the right materials
Outlet:Electronics Weekly

P-Channel MOSFET Tutorial with only Positive Voltages

From the mailbag (or chat… bag?)

Positive Voltages with a P-Channel MOSFET Tutorial

On every page of my blog, you might notice a chat window. If I’m not busy, we can chat in real-time. If not, the messages come to me by email. Here’s one I got from Matt the other day:

Let’s talk a bit about how (and why) you would use a P-Channel MOSFET. Matt, and he’s not the only one, is probably asking this question based on the “myth” that P-Channel MOSFETs require “negative voltage” supplies.

Keep reading for a how to use only positive voltage in this p-channel MOSFET tutorial.

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How to find parts for your electronics projects and designs

These are the tools I use to find parts, do you?

how-to-find-parts tips

What part is the most important part in building a project? All of them! Okay, bad joke. Selecting the right parts or components for a design is an area where both new hobbyist and veteran engineers struggle. The wide variety of devices make it almost impossible to know if you are selecting the right one.

Looking at a curated List, using component search engines and browsing DIY shops are how I tend to find parts for my projects.

You might want to bookmark these some of these sites so you can use them next time you’re stuck on how to find parts for your project.

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What’s the difference between Series and Parallel Circuits?

Example of Circuit and Parallel Circuits

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.

In short if the same current flows through all the parts, they are in series.  While if current has different paths, they are in parallel.  Keep reading to dive into this tutorial on how ohm’s law applies to series and parallel circuits.

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Awesome 3D Board (BRD) Viewer for EAGLE

3D Render of MSO Demo Board

3D Render of MSO Demo Board

Earlier I posted a PCB Checklist of items to double-check when sending your board out to a fab. The Dangerous Prototypes blog pointed to a 3D EAGLE PCB tool from a Bulgarian-based developer called Cytec that takes an EAGLE BRD file and renders it in 3D for you.

The example board I have above is a render of my MSO Demo Board. And I have to be honest, it looks much like that one! (more…)

Never trust an autorouter

I am not a fan of relying on the Autorouter in EAGLE — or any PCB CAD software for that matter. When laying out a board, I’ll use the autorouter to get an idea if the part placement is going to work or not. In this case, I was reminded how much autorouters suck! Even after running for while, the autorouter could only route up 50% of the nets (signals).

Never Trust The Autorouter

As Chris Gammell‘s T-Shirt Says, Never Trust The Autorouter.

It only took me about 20 minutes to start over and finish the manual layout. I still want to clean it up a little, but over all, I beat the Autorouter.

What is the board anyway?

In January I visited Tokyo on my annual work trip. While there, I ran over to Akihabara to check out a used media store called Traders. The multi-level store (like all those in Tokyo) sold used video games and movies. Each floor featured different platforms. My favorite was the 2nd floor which was all retro 8, 16, and 32 bit systems. Piles of Famicoms (NES), Super Famicoms (SNES), Mega Drives (Genesis), and other systems were all around. In the middle of the floor were racks of cartridges.

While there I picked up a couple of Rockman (Mega Man) carts, Super Mario brothers, and even Adventure island.

A US-based NES can play Famicom games since the basic hardware is the same. However, the pin outs are slightly different. Also, US-based NES systems look for a lock-out ship (CIC) that Famicoms don’t have. Fortunately I ran across a project that uses the ATtiny (AVRCICZZ) to emulate the lockout chip. So armed with that and some pinouts, I’ve created an adapter.

Keep subscribed, after a few more touches, I’ll post the EAGLE files as an Open Source Hardware (OSH) project.

iCircuit’s circuit simulator goes from iOS to Desktop

When it comes to schematic capture and circuit simulation on a mobile device, iCircuit for iOS got it right from the start. iCloud integration, intuitive touch controls, and fast application performance. Now (or Finally?), my favorite mobile circuit simulator, iCircuit, is available for OS X.

iCircuit with 555 Timer

iCircuit is based on the Falstad Circuit Simulator, which sadly, is a Java-based web app. For years I’ve installed the App on my iPhone and iPad almost immediately after turning on iCloud [for Android users, that’s basically the first step of activating an iOS device].

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Clean Ground Planes on DIY Boards

If you’re making your own PCB with the toner transfer method, you might find that getting nice clean ground planes is difficult. John on twitter (@johngineer) realized a simple, but effective method.


Use a hatch pattern for your planes and then fill in the squares with a Sharpie. Simple, but effective. The paper detaches easier and the etch comes out cleaner.

For help on creating ground planes in EAGLE, check out this video tutorial I put together.

Signal and Power Integrity Cover

Signal and Power Integrity – Simplified (2nd Edition) ( Prentice Hall, 2009)

Let me start by saying, this book is not for new comers, or (ugh) “newbies”, to electronics.  This book is intended for those who have a solid understanding of electrical engineering fundamentals, but want to expand to the next level.  Bogatin’s amount of detail is on-par with a textbook but writing style is more casual.

Understanding signal integrity use to be “Black Magic.”  It is taught in a language which resembles engineering speak, but sounds like randomly assembled terms purposefully meant to confuse people.  Personally, I remember hearing “signal integrity engineers talk” and wondered if they were speaking in code.

Review: 5 out of 5