<story><title>Don’t use 7-segment displays (2011) [pdf]</title><url>http://www.harold.thimbleby.net/cv/files/seven-segment.pdf</url></story><parent_chain></parent_chain><comment><author>afandian</author><text>In Oxford city centre, and probably elsewhere, they replaced the live signage at bus stops. These tell you when the next bus is due, the time and date, etc.&lt;p&gt;They used to be amber LED matrixes. High contrast, high legibility, low resolution.&lt;p&gt;Now they are colour LCD panels. High resolution, high tech, probably high cost. Now they can show the logos of the bus operators, smooth scrolling text and any arbitrary images. None of which anyone really needs except perhaps the egos of the bus companies.&lt;p&gt;And they are &lt;i&gt;completely illegible&lt;/i&gt;. The viewing angle is limited, the text is smaller, unnecessary stuff is there because the implementors can.&lt;p&gt;Careful what you ask for.</text></comment>
<story><title>Don’t use 7-segment displays (2011) [pdf]</title><url>http://www.harold.thimbleby.net/cv/files/seven-segment.pdf</url></story><parent_chain></parent_chain><comment><author>exmadscientist</author><text>Many of the author&amp;#x27;s points are worth consideration (especially regarding use of 7-segment displays for anything other than digits), but come on:&lt;p&gt;&amp;gt;  A bespoke display panel was used; itwould have been safer, easier to read, more versatile, andcheaper had a hi-res display been used&lt;p&gt;Obviously the author has never actually tried to design a product both ways. Displays are &lt;i&gt;expensive&lt;/i&gt;, and I&amp;#x27;m not just talking about the panel itself. Usually you must go up a level or two on your processor hierarchy: a 7-segment display or matrix can be driven by a 4-bit microcontroller. A VGA-resolution display will require a high-end microcontroller, usually a 32-bit Cortex-M3 or M4 these days. A true &amp;quot;hi-res&amp;quot; display, which has admittedly drifted up in quality since the author wrote this, will push you into application processor (i.MX) territory.&lt;p&gt;That may not sound like much, but typical costs for those levels &lt;i&gt;including supporting circuitry&lt;/i&gt; are in the neighborhood of $1, $10, and $100. This is because the tiny microcontroller needs nothing; the fancy apps processor needs DDR SDRAM, NAND flash, a PMIC, and is probably a BGA you have to route on an 8-layer board, with GHz MIPI signalling flying around, and don&amp;#x27;t even get me started on the software complexity.... You can do all of these things, and if it genuinely makes your product better, you &lt;i&gt;should&lt;/i&gt;. But do not pay the cost if your product does not benefit.&lt;p&gt;A coworker of mine likes to tell a story about cutting the sales price of a medical device from $5,000 to $500. The main source of that savings would have been removing the display. (Yes, really. Medical displays are expensive.) This was rejected by product management, on the reason that &amp;quot;The people who buy this stuff are not the people who use it. The people who buy it like shiny-looking things. It is much easier to sell a product that looks complicated and expensive to a procurement officer than one that looks simple and possibly less advanced, even if they are the same inside. That display does do something -- it sells units.&amp;quot;&lt;p&gt;In operation, the display had a bunch of whiz-bang crap that could have been deleted with no consequence, and two touch buttons for &amp;quot;arm&amp;quot; and &amp;quot;stop&amp;quot;. Of course, you had to use a physical button to actually activate it; IEC 60601 wouldn&amp;#x27;t allow using just a &lt;i&gt;touchscreen&lt;/i&gt; to start or stop a medical procedure! So the display really didn&amp;#x27;t do anything functional....&lt;p&gt;So, no, high-res displays are not always the answer. Think carefully about the cost!</text></comment>