We’ve all seen the caution us not to do idiotic things or remind us of the obvious. “Remove infant before folding stroller” and “Do not use toaster while bathing” are two examples that come to mind at random. But what about warning labels that really do need to convey important, non-obvious information? They can be stupid too.
If you’re designing a device that spends most or all of it’s time connected to a PC through a USB port, it is probably best to design USB connectivity right into the device. However, if the device only needs to be connected occasionally to change settings or download data logs, it might be convenient to use a separate adapter that translates USB protocol to TTL level asynchronus serial signals that talk to the microcontroller’s UART. Also, if you’re a hobbyist, you may not want to spend a lot of time understanding the details of USB interfacing hardware and protocols. I recently stumbled upon an adapter that makes this easy.
While some free finite element analysis software is available, the engineer or student can learn a lot about how FEA works by constructing a simple model from scratch in a commonly available spreadsheet program such as Excel. The technique presented here can simulate a two dimensional flat plate of uniform thickness. Each boundary element can be an arbitrary fixed-temperature or insulated. The resultant temperature of each active element is iteratively calculated by simply averaging the temperatures of the adjacent cells. Read the rest of this entry »
I recently saw a potential demand for a product that was essentially a seamless rectangular metal cup, about 1″ x 3″ on the open end and about 4″ deep. This sounded like a job for a process called “deep drawing.” In this process, a flat sheet of metal is punched through a die to form a cup shape.
Great, all I need are a few prototypes to verify the design, then a few tens of pieces for some tentative test marketing, and finally perhaps a few thousand a year for production. One problem: for a deep drawn part, a “short run” is considered “less than 60,000 pieces.” I could find only one company that could actually deliver sample parts, but none of their standard sizes were close enough to what I needed.
The town of Mora in Sweden is known for its traditional and utilitarian fixed-blade knives. Many survival and bushcraft experts recommend these simple and very inexpensive knives, especially for beginners. This article was originally posted by me on the Equipped to Survive Survival Forum.
This article explains why you might want to use mixed decay and how it is implemented in the A3977’s current chopper PWM scheme with the percent fast decay (PFD) pin.
Once you understand unidirectional PWM of an inductive motor load, we can expand the concept to a bidirectional h-bridge PWM circuit. Read the rest of this entry »
This article covers unidirectional Pulse Width Modulation (PWM) and how it can be used to control the power applied to a DC motor or the current in a stepper motor winding, for instance. While we eventually want to talk about doing bidirectional PWM with an h-bridge, we’ll start with a simple, one-direction control circuit.
An h-bridge is a bipolar driver circuit that is often used to control a load such as a brush type DC motor. This article covers the most basic concepts of a simplified h-bridge circuit. Later articles dig deeper into the details of practical h-bridge operation and design.
This article explains the important points in converting a standard Beckett AFG oil burner to burn waste motor oil, used ATF, fryer grease or waste vegetable oil in your experimental furnace, heater or boiler. Read the rest of this entry »