{"id":422,"date":"2014-08-04T23:06:47","date_gmt":"2014-08-05T04:06:47","guid":{"rendered":"http:\/\/www.lacentralrr.com\/Blog\/?p=422"},"modified":"2015-08-05T17:15:18","modified_gmt":"2015-08-05T22:15:18","slug":"optical-detection-explained","status":"publish","type":"post","link":"https:\/\/www.lacentralrr.com\/Blog\/2014\/08\/04\/optical-detection-explained\/","title":{"rendered":"Optical Detection Explained"},"content":{"rendered":"

Well, there I go again.\u00a0 Earlier I posted a column celebrating the completion of all the hardware and wiring for my optical detection system (well, it’s not really<\/em> complete….I still have to build the panels that will display the occupancy indicator LEDs).<\/p>\n

Problem is, I just assumed all readers would know what I was talking about.\u00a0 Not!\u00a0 I’ve been informed that I should quit assuming.<\/p>\n

So, I’ll try to explain in 3000 words or less, just what an optical detection system is.\u00a0 Now keep in mind that my explanation here is strictly in the context in which I am employing said detection system.\u00a0 And I will avoid getting into the directions that the electrons are traveling and the gory details of the circuitry that makes this all happen.<\/p>\n

I have six staging tracks, all of which are hidden from normal viewing.\u00a0 In order to ascertain where a train is while running on this track, I decided to employ a detection system.\u00a0 There are several ways to detect a train, and I chose to employ optical detection.\u00a0 The system utilizes photo-transistors (PTs) which can sense whether or not they are seeing light.\u00a0 When they do, they will turn on, that is, they act as a switch and will close a circuit.\u00a0 I have installed my PTs centered in the track between a pair of ties, with their tops just above the roadbed.\u00a0 The PTs are wired to a circuit board located under the layout.<\/p>\n

As a light source, I’m using infrared LEDs (IR-LEDs).\u00a0 To avoid seeing light beneath the layout, and to make the circuit less susceptible to ambient lighting, I chose to use components that are sensitive to light in the infrared range.\u00a0 This isn’t visible to the naked eye, and in fact, that’s what most TV remote controls use.\u00a0 The PTs and the IR-LEDs selected are matched to their light spectrum and work in harmony together.\u00a0 The IR-LEDs are mounted on the “towers” I spoke of in the last post, and are pointed down at the PTs.\u00a0 They are simply wired to a 12 volt DC bus (a pair of wires).<\/p>\n

The circuit board I mentioned above is the “brain” of the system.\u00a0 The inputs to the board are the PTs.\u00a0 The outputs are to plain old red LEDs which are used as indicators, installed on a simple panel with a track diagram.\u00a0 Each indicator LED is placed on the track diagram at the location where a PT sensor is located on the actual track.<\/p>\n

With the power on and the IR-LEDs shining brightly, the PTs see the light and the circuit board determines there is nothing out there as no PT is “closed”.\u00a0 Therefore, no power is supplied to the indicator LEDs on the panel.\u00a0 But when a train comes along, it blocks the light of an IR-LED shining on a PT below, and that PT turns on, which in turn lets the circuit board know that something is at that location.\u00a0 It in turn lights up the appropriate panel indicator LED and you now have a visual indication of where the train is.<\/p>\n

Simple, huh?<\/p>\n

Actually, it really is.\u00a0 I purchased the circuit boards already built up from a fellow hobbyist up in Canada.\u00a0 All I had to do was install the PTs and IR-LEDs, and wire them up.<\/p>\n

Your test will arrive in the mail later in the week.<\/p>\n

-Jack<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Well, there I go again.\u00a0 Earlier I posted a column celebrating the completion of all the hardware and wiring for my optical detection system (well, it’s not really complete….I still have to build the panels that will display the occupancy … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-422","post","type-post","status-publish","format-standard","hentry","category-electrical-dcc"],"_links":{"self":[{"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/posts\/422","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/comments?post=422"}],"version-history":[{"count":4,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/posts\/422\/revisions"}],"predecessor-version":[{"id":709,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/posts\/422\/revisions\/709"}],"wp:attachment":[{"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/media?parent=422"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/categories?post=422"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lacentralrr.com\/Blog\/wp-json\/wp\/v2\/tags?post=422"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}