Measurement Tools for Laying Out Circuit Boards and Enclosures

ruler   caliper - 300When laying out panels or circuit boards, accurate measurements are a must.  A few inexpensive tools can make excellent results much easier to achieve. 

I think we've all used rulers to try and measure parts.  For the fuse holder shown, it can be held against the ruler, the width estimated and the marks correctly interpreted to get a decent result.  The ruler shown is a high-quality metal ruler and it has metric units on the back.  I use a combination of inch and metric units depending on what size something is designed for - for example, in laying out PCB dimensions, I'll use whatever units the enclosure was designed in.  Usually, one system will provide nice numbers.

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EEVBlog #221: Lab Power Supply Design Part 1

EEVBlog 221Dave Jones at the EEVBlog has created another awesome video that's recommended viewing for all: 

EEVBlog #221:  Lab Power Supply Design Part 1.  Dave goes through all of the design considerations and calculations for a micro-controlled power supply.  He starts with the basic LM317 regulator for constant current and constant voltage and goes over the limitations.

Dave provides a great look at the design process and calculations involved.


 EEVblog #221 – Lab Power Supply Design – Part 1

 EEVblog #222 – Lab Power Supply Design – Part 2

 EEVblog #224 – Lab Power Supply Design – Part 3

EEVblog #225 – Lab Power Supply Design Part 4 – PWM Control

EEVblog #232 – Lab Power Supply Design Part 5

Note the link to the schematic on the above page.




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Andrew Carter's Blog - A Great Beginner's Resource


\Andrew Carter has a great series of blog articles covering the basics and not-so-basics of electronics components on the EEWeb site.  EEWeb is a great resource and worth checking out.

Andrew's articles so far include:

These short articles are definitely worth reviewing.  You might be surprised at what you'll learn.

Be sure to keep an eye on Andrew's posts.  I suspect many more winners are on the way.


 Updated List as of 27 December 2011

Here's a list of current blog topics.   Rather than spending an hour entering links to each section, follow the general link below.

  • Resistance, Resistors and Ohm’s Law
  • Capacitor Basics
  • Introduction to Carbon Composition Resistors
  • Overview of the Film Type Resistors
  • Get To Know the Wirewound Type Resistors
  • How to Read Resistor Color Coding Scheme
  • Capacitors in Series
  • Capacitors in Parallel
  • Resistor Values Calculation
  • Series Combination of Resistors
  • Dealing with Surface Mount Resistors
  • Learning About Resistors in Parallel
  • Know More about Voltage Divider Circuits
  • Series-Parallel Combinations of Resistors
  • A Look at the Power Rating of Resistors
  • Getting To Know the Potential Difference
  • Behavior of Resistors in AC Circuits
  • Identifying the Characteristics of Capacitors
  • Let’s Talk About Capacitance and Charge
  • Parallel Connections of Capacitors
  • Characteristics of Inductors
  • Studying the Color Codes of Capacitors
  • Getting Familiar with Capacitors
  • What’s More Inside A Capacitor
  • Capacitor Types
  • Series Connections of Capacitors
  • How Capacitors Behave in AC Circuits
  • Choosing the Type of Inductor
  • Inductance, Power and Energy of an Inductor
  • The Basics of Inductor
  • More of Self Inductance and Mutual Inductance
  • Series Connection of Inductors
  • Parallel Connection of Inductors
  • Inductive Reactance
  • RL Circuits
  • The Basics of Semiconductors
  • Describing the P-N Junction
  • Introduction to Diodes
  • Types of Diodes

Andrew Carter's Blog

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Controlling a clock with an Arduino

Here's another great article I found via Hack-A-Day about controlling the ubiquitous quartz clock movements that are all over the place.  Cibo Mahto explains how to easily control one of these using an Arduino but the same technique applies when using a PIC.  The clock coil needs to be energized in a positive direction and in the opposite direction for each "tick" which is easily done by connecting it between a pair of port pins and toggling one pin high, the other low and then reversing the process.  This makes it possible to control time - at least as indicated on one clock!  Pulse faster than 1 Hz (once per second) and the clock speeds up.  Slower and it slows down.

Cibo's article has all the details.  There's plenty of explanation so doing this with any micro and language will be a piece of cake.

Controlling a clock with an Arduino

Update: The Arduino system is fine; the only thing you have to take into consideration is the 9.54 hour rollover event, which Rob Faludi has provided an excellent solution for here. I made up a nice little over-analysis of the issue, available here.

I have been wanting to make a variable-speed clock for a while, so this weekend I picked up a cheapish clock unit (thrift stores are a great source!), and played around with using the Arduino to control it. In summary, I was able to get everything going, but there are some issues with the Arduino software that are going to prevent making it a really accurate clock. Explanation, source code after the break.

Clock controller circuit

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Spiralbrain's Blog: PIC Kit 2 IR capture tool

An awesome use for a PICkit 2, via Hack-A-Day.  Note that this only works with a PICkit 2 - the upgraded PICkit 3 does not include the logic analyzer function.


PIC Kit 2 IR capture tool

The PIC Kit 2 is a brilliant tool that can be used as a programmer, debugger, serial receiver and for signal capture. In many ways it is more versatile than the PIC Kit 3. One of my projects required IR capture to duplicate remote codes. I decided to create this small module that plugs directly on the PIC Kit 2 and can be used to capture IR codes for almost any IR remote available today. The software supplied from Microchip also allows to approximately measure the timing which makes it quite handy.

The circuit is pretty simple and can be wired in 5-10 minutes

Read the entire story at Spiralbrain's Blog.

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Low Cost Enclosures

vm in box - 300I'm always on the lookout for low cost, nice looking enclosures.  I'll present a method of easily making a custom enclosure that looks great on the bench or anyplace else in the house.  I touched on this technique in my various comments on the TAP-20 Power Monitor - here I'll spell out the details.  Enclosures of this type are perfect for projects using an LCD or LED display, and minimize the machining a panel requires.


A small wood box or frame and a plastic panel make a great enclosure.  Clear or colored transparent plastic can be used so that an LCD or LED display or LED indicators can show through the panel with no cutouts required.  Cutting nice openings can be a downfall, so this works well.

The first step is to find a box or frame of suitable dimensions for your planned application.  A box with a back is great for "finished" projects where you don't need access to the internal circuit boards.  For a dev system or projects under development, a frame with an open back allows access for cables, programming and changing things around.

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Design News: Getting Started With Proximity Sensing



Jon Titus, Contributing Editor


The Vishay Semiconductors VCNL4000 reflectance proximity sensor combines an infrared (IR) LED and a photodetector with a second sensor that measures ambient light with a spectral response close to that of a human eye. The small sensor IC can detect an object out to about 20cm. Vishay suggests possible uses in smartphones, digital cameras, and tablet PCs. Other ideas include: hands-free light dimmers, pet door openers, industrial safety apparatus, etc.

The kit allows engineers to work with the small IC on a USB stick controlled by Vishay's measurement-and-control graphical user interface (GUI). I recommend the kit but with a few reservations about the quality of the accompanying manual. You must decipher many sentences and try to determine what the authors mean. I had hoped for real-world examples, which the otherwise good application information lacks.

The $35 kit worked well, and the software plotted signals from the sensor that takes into account and rejects ambient light. Software reads from or writes to 11 registers via an on-chip I2C port to set operating conditions such as LED current (10mA to 200mA), an ambient light parameter, and 16-bit ambient light and proximity values.

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Dave has posted EEV Blog #186, covering surface mount soldering techniques.

"Now the 1206 is an absolute monster.  Steveie Wonder could solder this thing!  It is so damned easy."

Recommended viewing.


Using Fixed Voltage Reference (FVR) for A/D conversion in enhanced mid-range PIC microcontrollers

Here's another great article from Embedded Lab.  The FVR (fixed voltage reference) is included in the 18Fk-series parts with various capabilities.

The reference voltage plays a very important role in any A/D conversion. It determines both the range and the resolution (Volt/Count) of the A/D conversion. Besides, the accuracy of the conversion also depends upon how stable the reference voltage is. Usually in PIC microcontrollers, the reference voltage for A/D conversion can be selected as the supply voltage itself or provided externally through one or more I/O pins. But the new enhanced mid-range family of 8-bit PIC microcontrollers have a built-in module that generates a stable reference voltage internally. It is called Fixed Voltage Reference (FVR) where the output is very stable and independent of the supply voltage (VDD). The output of the FVR can be configured to supply a reference voltage for A/D conversion internally. This article describes how to configure the FVR module to derive the reference voltage of 2.048 V for A/D conversion in PIC16F1827 microcontroller. The analog signal for this experiment is taken from the output of a LM34DZ temperature sensor. After the A/D conversion, the PIC16F1827 displays the temperature on a 2×8 character LCD.

Isn't this an awesome board layout on perfboard?

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Related article from Embedded Lab: Voltage monitor for car’s battery and its charging system

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A Lesson Learned the Hard (and Expensive) Way

The following is from Gary's Blog on EEWeb.  Think you know what happened?  Click the link at the end to read the read of the blog and learn an important lesson.

How to Destroy Data and Hardware, Wholesale.

So a nice holiday weekend, I decide to reorganize my home office and set up some extra equipment I had sitting around. I pull everything out, unplug all the cables, and dress everything up nicely. I add a network hub, and set up an old PC that I use occasionally, and added the power wall wart to the USB hub I’d been using. Also fixed and set up a scanner. It all looked great and I had more workspace as well.

After that, I did have a few hours of work to do for a client, and the latest files were on a thumb drive so I plugged that in and sat down to work. Odd, it doesn’t recognize the thumb drive. I try another one, and it doesn’t see that one either. Hmmm, no external USB HD as well. Plugging directly into the PC USB ports doesn’t work either, but my keyboard and mouse are working OK. Ah, I think I’ve heard of this – Win 7 not recognizing USB mass storage devices. A quick check of the Googlenet, confirms that this is probably the problem. Unplug everything, reboot, uninstall/reinstall drivers. Nope. Roll back the last Windows update. Nope. Stumped.

Well, it’s getting late, and I have work to do, I can get the files off the thumb drive on another PC. Plug it in, and* that *PC doesn’t recognize it either. Same for the other thumb drive. What the flock is going on!

Think you have the answer?  Read the rest of the story.

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