What is a Varistor

Added a new page to better cover the Definition of a Varistor. I had a graphic of the body of a varistor along with its dimensions and I figured it would be better just to place it on a different page, instead of trying to fit it on a current page. So the page has a few graphics and so far the same definition that was already on the site.

There are a number of pages that link in; Companies that make Varistors, Resistor Definitions, Definition of a MOV, and the original Varistor Definition. Of course the Varistor page was also added the site map which holds all the pages address located on the Engineering Site. The site-map is also located off-site, at another web address.

So that's not a bad start with four incoming page links, this blog posting, an external link from the sitemap and a few graphics. Ok, not that much text, that will change in time. Better than a lot of other pages just starting off.

FMVSS138 Tire Pressure Monitoring System

I was scanning the web yesterday and I came across a new vehicle interface, or maybe a vehicle system. The new interface is called the Tire Pressure Monitoring System or TPMS. The TPMS standard requires cars and trucks to have an early warning system to alert the driver that one or more tires on the vehicle is below their rated tire pressure. The standard went into effect around 2006, but this was the first I ever heard of it. I drive a 2006 Ford Mustang but I don't remember ever seeing it light, so it didn't make it to my model year.

The links pointing to the page include a 'T' Buses page, Electrical Interface Buses page the Engineering Acronyms page and the Definition of Torque page [first term on the page].

So we get another idiot light on our dash-board. However the TPMS light shows a tire to indicate a 'flat' instead of the engine-symbol light used by OBDII which nobody could ever figure out [check engine]. Now TPMS really indicates low tire pressure and not a flat, but one of the possible symbols appears to be a flat tire

Now it's not really an electrical bus, but it could be an electrical interface so that's why I listed it. I also added the spec to the web site so I wouldn't have to try and figure out what it was a few years from now. Apparently this standard does not really depend on any defined electrical or physical interface, it just has to perform its function.

74244 Octal Buffer

Added a new page to show some details regarding the 74244 Octal Buffer. I was adding the page to have a link of one of the interface bus pages, but now I can't remember which interface uses the 74244 buffer. This particular buffer is a 74HCT244 which comes in a 20-pin PSOP, so a link from that page points to it too.

A link also points in from the main Functional IC Schematics page, and the individual page that covers 16-bit Buffer ICs. Like all other new pages I also added a link to the Engineering Sitemap for the Engineering Web Portal.

The link text used for the last two links are used so the search engine sees something other than a link to 'home' or 'sitemap'.

Logic True Tables

I added a new page to hold a Glue Logic Truth Table covering each of the standard logic functions. The graphic already resided on the web site but was accessed by link to a graphic stored out on Picasa. So no new data was added, just moved onto a new page to hold the graphic. So far the new page is linked from the two other pages that had already pointed to the graphic; Definition of Triac [first term on the page], and the page on Glue Logic Timing.

So the Engineering Portal gets a new page, but at the same time it should be a page that will see little if any visitors. It's a common search term with no page text so maybe it will get some internal traffic, but should not see any from a search engine.

The point was not to generate a page which will never been seen. The original graphic was a 100k bit-map file stored out on Picasa, while the new file is stored on my server and only takes up 30k bits. So my server will see a 30k hit each time the page is viewed, it was zero while the pic file was stored off-site.

It's Google's view that a file on another server requires another DNS look-up [to find it] which slows the site down, and of course the new file is 70k smaller. Google started to also rate web sites on speed in addition to all the other things Google rates a site on. So this change makes the site appear faster to Google [a computer], but a visitor would never notice.

It's also better to have a picture embedded within the site and not just use a pointer out to some other server that holds pic files. The attached graphic is a pic of an AND gate and the true table for that AND gate.

Composite Video Connection

I added a new page to cover Composite Video. The video interface was always listed on the Video Buses page, but because there were to many graphics associated with Composite Video I moved the topic to a new page. The link was also added to the Cable Buses page, Interface Buses 'C' and the list of all Interface Buses.

Except for the graphic no new information was added, this is an out of date interface. I still use it to connect to my older VHS tape decks, but I really stopped using the VHS stuff years ago.

I didn't check for any other page to page links pointing to the Composite Video topic, because the links on that page still work, or point to the new page. The attached graphic is one of the Sony Stereo AV receivers I have, I think this one is a 6.1 channel amplifier. I also have another 7.1 Sony receiver which is just about the same.

The receiver has 6 video channels using the Red/White/Yellow Composite video, including; TV/SAT, DVD, Video 1 and Video 2 and a single Yellow composite video connection for a monitor. Three channels of component video are also shown [Green/Blue/Red].