Author Archives: Bob Baddeley

WTF are Ground Loops?

Posted on by

These magical creatures crop up out of nowhere and fry your electronics or annoy your ear holes. Understanding them will doubtless save you money and hassle. The ground loop in a nutshell is what happens when two separate devices (A and B) are connected to ground separately, and then also connected to each other through some kind of communication cable with a ground, creating a loop. This provides two separate paths to ground (B can go through its own connection to ground or it can go through the ground of the cable to A and then to A’s ground), and …read more

Continue reading WTF are Ground Loops?→

PCB Design Guidelines to Minimize RF Transmissions

Posted on by

There are certain design guidelines for PCBs that don’t make a lot of sense, and practices that seem excessive and unnecessary. Often these are motivated by the black magic that is RF transmission. This is either an unfortunate and unintended consequence of electronic circuits, or a magical and useful feature of them, and a lot of design time goes into reducing or removing these effects or tuning them.

You’re wondering how important this is for your projects and whether you should worry about unintentional radiated emissions. On the Baddeley scale of importance:

  • Pffffft – You’re building a one-off project that

…read more

Continue reading PCB Design Guidelines to Minimize RF Transmissions→

Tools of the Trade – Thermoforming

Posted on by

Chances are good that you’ve already lost some blood to thermoforming, the plastics manufacturing process that turns a flat sheet of material into an unopenable clamshell package, tray inside a box, plastic cup, or leftover food container.  Besides being a source of unboxing danger, it’s actually a useful technique to have in your fabrication toolchest. In this issue of Tools of the Trade, we look at how thermoforming is used in products, and how you can hack it yourself.

The process is simple; take a sheet of plastic material, usually really thin stuff, but it can get as thick as …read more

Continue reading Tools of the Trade – Thermoforming→

Tools of the Trade – Injection Molding

Posted on by

Having finished the Tools of the Trade series on circuit board assembly, let’s look at some of the common methods for doing enclosures. First, and possibly the most common, is injection molding. This is the process of taking hot plastic, squirting it through a small hole and into a cavity, letting it cool, and then removing the hardened plastic formed in the shape of the cavity.

The machine itself has three major parts; the hopper, the screw, and the mold. The hopper is where the plastic pellets are dumped in. These pellets are tiny flecks of plastic, and if the …read more

Continue reading Tools of the Trade – Injection Molding→

Should You Outsource Manufacturing? A Handy Guide

Posted on by

A lot of people assume that the product development cycle involves R&D, outsourcing to a Chinese manufacturer, and then selling the finished product. It’s almost ingrained in our heads that once a prototype has been developed, the next step involves a visa and airplane tickets. Here is a guide that will explore a few other options, and why outsourcing may not be appropriate for everyone.

First, let’s talk about goals. We’ll assume you’re not a large company, and that you don’t have a huge budget, and that you’re just getting started with your product and don’t have big volumes; a …read more

Continue reading Should You Outsource Manufacturing? A Handy Guide→

Using The FCC EAS For Fun And Profit

Posted on by

When a consumer electronics device is sold in the US, especially if it has a wireless aspect, it must be tested for compliance with FCC regulations and the test results filed with the FCC (see preparing your product for FCC testing). These documents are then made available online for all to see in the Office of Engineering and Technology (OET) Laboratory Equipment Authorization System (EAS). In fact, it’s this publishing in this and other FCC databases that has led to many leaks about new product releases, some of which we’ve covered, and others we’ve been privileged enough to know about …read more

Continue reading Using The FCC EAS For Fun And Profit→

Preparing Your Product For The FCC

Posted on by

At some point you’ve decided that you’re going to sell your wireless product (or any product with a clock that operates above 8kHz) in the United States. Good luck! You’re going to have to go through the FCC to get listed on the FCC OET EAS (Office of Engineering and Technology, Equipment Authorization System). Well… maybe.

As with everything FCC related, it’s very complicated, there are TLAs and confusing terms everywhere, and it will take you a lot longer than you’d like to figure out what it means for you. Whether you suffer through this, breeze by without a hitch, …read more

Continue reading Preparing Your Product For The FCC→

Books You Should Read: Poorly Made In China

Posted on by

This book is scary, and honestly I can’t decide if I should recommend it or not. It’s not a guide, it doesn’t offer solutions, and it’s full of so many cautionary tales and descriptions of tricks and scams that you will wonder how any business gets done in China at all. If you are looking for a reason not to manufacture in China, then this is the book for you.

The author is not involved in the electronics industry. Most of the book describes a single customer in the personal products field (soap, shampoo, lotions, creams, etc.). He does describe …read more

Continue reading Books You Should Read: Poorly Made In China→

Hackaday Dictionary: Mux/Demux

Posted on by

In this issue of Hackaday Dictionary, we cover the multiplexer and demultiplexer (also called mux and demux). They are essentially opposites but they work on the same principle. There are three parts: the input, the output, and the selector.

The Basics

With a mux, you have multiple inputs, and a selector chooses which one of those outputs to use, and pipes it to a single output. It’s as if a bunch of people want to say something to you at once, but you can only listen to one at a time.

With the demux, a single input is piped to …read more

Continue reading Hackaday Dictionary: Mux/Demux→

Tools of the Trade – Test and Programming

Posted on by

In our final installment of Tools of the Trade (with respect to circuit board assembly), we’ll look at how the circuit board is tested and programmed. At this point in the process, the board has been fully assembled with both through hole and surface mount components, and it needs to be verified before shipping or putting it inside an enclosure. We may have already handled some of the verification step in an earlier episode on inspection of the board, but this step is testing the final PCB. Depending on scale, budget, and complexity, there are all kinds of ways to …read more

Continue reading Tools of the Trade – Test and Programming→