http://www.raspberryvi.org/Raspberry Pi hacking for the visually-impairedenContents © 2021-03-10 09:37 <a href="mailto:mike@raspberryvi.org">Mike Ray</a> <a rel="license"> <p>Unless otherwise stated all content released under the <a href="http://creativecommons.org/licenses/by-nc-sa/4.0/"> <img alt="Creative Commons License BY-NC-SA" style="border-width:0; margin-bottom:0px;" src="http://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png"> </a> </p> Wed, 10 Mar 2021 09:37:12 GMTNikola (getnikola.com)http://blogs.law.harvard.edu/tech/rsshttp://www.raspberryvi.org/posts/power-equations.htmlMike Ray<div><h3 class="no_toc" id="table-of-contents">Table of Contents</h3> <ul id="markdown-toc"> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#introduction" id="markdown-toc-introduction">Introduction</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#the-units-of-measure" id="markdown-toc-the-units-of-measure">The Units of Measure</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#power" id="markdown-toc-power">Power</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#voltage" id="markdown-toc-voltage">Voltage</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#current" id="markdown-toc-current">Current</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#a-triplet-of-equations" id="markdown-toc-a-triplet-of-equations">A Triplet of Equations</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#simple-example" id="markdown-toc-simple-example">Simple Example</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#how-big-does-my-resistor-have-to-be" id="markdown-toc-how-big-does-my-resistor-have-to-be">How Big Does My Resistor Have to be?</a></li> <li><a href="http://www.raspberryvi.org/posts/power-equations.html#its-a-law-jim-but-not-as-we-know-it" id="markdown-toc-its-a-law-jim-but-not-as-we-know-it">Its a Law Jim, but not as we Know it</a></li> </ul> <h3 id="introduction">Introduction</h3> <p>In this blog post I will attempt to explain another triplet of equations that are very important to electronic theory.</p> <p>These are the three equations we can use to calculate power, in Watts, when we know Voltage and current, Voltage when we know power and current, or current when we know power and voltage.</p> <p><a href="http://www.raspberryvi.org/posts/power-equations.html">Read more…</a> (3 min remaining to read)</p></div>electronicstheoryhttp://www.raspberryvi.org/posts/power-equations.htmlTue, 09 Mar 2021 07:18:00 GMThttp://www.raspberryvi.org/posts/arduino-uno-board-description.htmlMike Ray<div><h3 class="no_toc" id="table-of-contents">Table of Contents</h3> <ul id="markdown-toc"> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#introduction" id="markdown-toc-introduction">Introduction</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#orientation" id="markdown-toc-orientation">Orientation</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#top-row-of-female-connections" id="markdown-toc-top-row-of-female-connections">Top Row of Female Connections</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#bottom-row-of-female-connections" id="markdown-toc-bottom-row-of-female-connections">Bottom Row of Female Connections</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#icsp-in-circuit-serial-programming-bus-pins" id="markdown-toc-icsp-in-circuit-serial-programming-bus-pins">ICSP (in circuit serial programming) Bus Pins</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#other-features" id="markdown-toc-other-features">Other Features</a></li> <li><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html#additional-notesquestions" id="markdown-toc-additional-notesquestions">Additional notes/questions</a></li> </ul> <h3 id="introduction">Introduction</h3> <p>Below is a description of the <a href="https://www.arduino.cc/en/guide/introduction">Arduino</a> Uno board.</p> <p>Including tables showing the function of each of the pins in each of the two rows of connectors, along opposite edges of the board.</p> <p><a href="http://www.raspberryvi.org/posts/arduino-uno-board-description.html">Read more…</a> (3 min remaining to read)</p></div>ArduinoelectronicsMCUhttp://www.raspberryvi.org/posts/arduino-uno-board-description.htmlMon, 08 Mar 2021 14:05:46 GMThttp://www.raspberryvi.org/posts/icsp-pinouts.htmlMike Ray<div><p>The ICSP (In Circuit Serial Programming) bus constists of six pins in a 2 x 3 box. Arranged like the cans in a six-pack.</p> <p>The pins are 1 and 2 in the top row, left to right, 3 and 4 in the centre row, left to right and pins 5 and 6 in the bottom row, left to right. As shown in the following table.</p> <p><a href="http://www.raspberryvi.org/posts/icsp-pinouts.html">Read more…</a> (2 min remaining to read)</p></div>ArduinoelectronicsMCUpinoutshttp://www.raspberryvi.org/posts/icsp-pinouts.htmlMon, 08 Mar 2021 13:24:24 GMThttp://www.raspberryvi.org/posts/battery-iron-soldering.htmlMike Ray<div><p>I've been doing hobby electronics since I was first old enough to be trusted with a soldering iron and not to burn myself, or burn the house down.</p> <p>So, after I lost my sight, soldering became a problem and a very upsetting loss.</p> <p>I have only recently felt very strongly that I wanted to find a way of doing some sensible soldering and hobby electronics again.</p> <p>I acknowledge that I am not going to be soldering QFP surface-mount SoC chips or MCUs any time soon. But I have found some techniques which mean I can now manage most of the typical old 0.54mm (0.1 inch) pitch through-hole components and boards.</p> <p><a href="http://www.raspberryvi.org/posts/battery-iron-soldering.html">Read more…</a> (3 min remaining to read)</p></div>electronicssolderinghttp://www.raspberryvi.org/posts/battery-iron-soldering.htmlWed, 03 Mar 2021 22:04:35 GMThttp://www.raspberryvi.org/posts/4001-pinouts.htmlMike Ray<div><p>This blog post shows the truth table for a 2 input NOR gate and the pinouts of the common 4001 CMOS quad 2 input NOR gate chip.</p> <p>With thanks to Anthony McCloskey, from the raspberry-vi mailing list for the suggestion of this post and the pinouts.</p> <p><a href="http://www.raspberryvi.org/posts/4001-pinouts.html">Read more…</a> (1 min remaining to read)</p></div>componentselectronicspinoutshttp://www.raspberryvi.org/posts/4001-pinouts.htmlMon, 01 Mar 2021 11:04:32 GMThttp://www.raspberryvi.org/posts/smith-kettlewell.htmlMike Ray<div><p>The <a href="https://www.ski.org/smith-kettlewell-technical-file/">Smith-Kettlewell Technical File</a> was a file published between 1980 and 1998, for blind and visually-impaired electronics professionals and enthusiasts.</p> <p>It contains a great amount of electronic data.</p> <p><a href="http://www.raspberryvi.org/posts/smith-kettlewell.html">Read more…</a> (1 min remaining to read)</p></div>componentselectronicslinkshttp://www.raspberryvi.org/posts/smith-kettlewell.htmlSun, 28 Feb 2021 11:53:40 GMThttp://www.raspberryvi.org/posts/741-pinouts.htmlMike Ray<div><p>The 741 operational amplifier is one of those chips you will probably encounter in college or high school technology and electronics classes.</p> <p>It has been around almost as long as integrated circuits.</p> <p>The name 'operational amplifier' comes from the fact that the amplifier was used in early analogue computers to perform 'operations' such as adding and subtracting analogue values.</p> <p>The text below explains the packaging of a 741 operational amplifier chip in the classic eight pin DIL chip package, and the table shows the pinouts.</p> <p>DIL = 'Dual in line'.</p> <p><a href="http://www.raspberryvi.org/posts/741-pinouts.html">Read more…</a> (1 min remaining to read)</p></div>componentselectronicspinoutshttp://www.raspberryvi.org/posts/741-pinouts.htmlSat, 27 Feb 2021 11:44:11 GMThttp://www.raspberryvi.org/posts/555-pinouts.htmlMike Ray<div><p>The 555 timer chip is one of the most ubiquitous chips seen in hobby and college electronics over about the last 45 years or so. Certainly before digital electronics and microcontrollers made such an impact.</p> <p>First invented in 1972, this chip is probably a contender for the most manufactured chip in the history of integrated circuits.</p> <p>The text below explains the packaging of a 555 timer in the classic eight pin DIL chip package, and the table shows the pinouts.</p> <p>DIL = ‘Dual in line’.</p> <p><a href="http://www.raspberryvi.org/posts/555-pinouts.html">Read more…</a> (1 min remaining to read)</p></div>componentselectronicspinoutshttp://www.raspberryvi.org/posts/555-pinouts.htmlSat, 27 Feb 2021 10:11:09 GMThttp://www.raspberryvi.org/posts/capacitors-in-series-and-parallel.htmlMike Ray<div><p>This post explains how to calculate the value of the overall capacitance of more than one capacitor, both in series and in parallel.</p> <p>Capacitors have limited application in digital circuits, including those we might use in conjunction with either a <a href="https://www.raspberrypi.org/">Raspberry Pi</a> or some variety of microcontroller.</p> <p>But you will find them as the second component in a classic RC timing circuit, where a capacitor is charged through a resistor, to produce some kind of event after a predictable length of time, or in decoupling noise (ripple) to ground.</p> <p>Where capacitors are also often used is in a DC blocking application. To couple AC, such as audio or radio frequency into the next stage of a circuit, but block the DC from the previous stage.</p> <p><a href="http://www.raspberryvi.org/posts/capacitors-in-series-and-parallel.html">Read more…</a> (1 min remaining to read)</p></div>componentselectronic theoryelectronicshttp://www.raspberryvi.org/posts/capacitors-in-series-and-parallel.htmlSat, 27 Feb 2021 08:51:55 GMThttp://www.raspberryvi.org/posts/7400-pinouts.htmlMike Ray<div><p>For many years the 7400 quad 2 input NAND gate chip was the backbone of digital electronics. Because using a mass of NAND gates it is possible to construct almost any digital system. Although by today’s standards it would not be the pinnacle of miniaturisation.</p> <p>This post shows the truth table for a 2 input NAND gate and the pinouts of the common 7400 quad 2 input NAND gate chip.</p> <p>With thanks to Anthony McCloskey, from the raspberry-vi mailing list for the suggestion of this post and the pinouts.</p> <p><a href="http://www.raspberryvi.org/posts/7400-pinouts.html">Read more…</a> (2 min remaining to read)</p></div>componentselectronicspinoutshttp://www.raspberryvi.org/posts/7400-pinouts.htmlFri, 26 Feb 2021 19:08:48 GMT