{"id":8387,"date":"2017-10-15T16:40:45","date_gmt":"2017-10-15T16:40:45","guid":{"rendered":"http:\/\/localhost:8105\/?p=8387"},"modified":"2021-12-07T16:44:57","modified_gmt":"2021-12-07T16:44:57","slug":"pushbuttons-switches-featuring-built-in-led","status":"publish","type":"post","link":"https:\/\/blog.shahada.abubakar.net\/?p=8387","title":{"rendered":"Pushbuttons Switches featuring built-in LED"},"content":{"rendered":"\n<p>I found these push button switches have a built-in LED in the center. Looks like it is time to revisit the 737FMC project, this time with Version 3 featuring backlit buttons?<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"1024\" src=\"https:\/\/blog.shahada.abubakar.net\/wp-content\/uploads\/2021\/12\/20171016_001604-768x1024.jpg\" alt=\"\" class=\"wp-image-9010\" srcset=\"https:\/\/blog.shahada.abubakar.net\/wp-content\/uploads\/2021\/12\/20171016_001604-768x1024.jpg 768w, https:\/\/blog.shahada.abubakar.net\/wp-content\/uploads\/2021\/12\/20171016_001604-225x300.jpg 225w, https:\/\/blog.shahada.abubakar.net\/wp-content\/uploads\/2021\/12\/20171016_001604.jpg 1125w\" sizes=\"auto, (max-width: 768px) 100vw, 768px\" \/><\/figure>\n\n\n\n<p>The yellow version is a bit closer to orange (a lot more orange than in the photo below), but I think it\u2019s fine. The LED is on a separate circuit from the switch itself.<\/p>\n\n\n\n<p>They are USD15.20 + 2.49 shipping for a pack of 100 from AliExpress (https:\/\/goo.gl\/KtKj3C)<\/p>\n\n\n\n<p>Stuff to solve:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Wiring. There are 69 keys altogether on the 737 FMC CDU. Ledcalc.com shows one current limiting resistor with 4 LEDs in series. Why 4?<ul><li>ANSWER: It\u2019s to do with the voltage drop from each LED. If each LED drops 2.4V, then with a 5V supply you can only have 2 LEDs in series under one current limiting resistor, and with a 12V supply you can only have 4 LEDs in series under one current limiting resistor. The other LEDs have to be run in parallel, and therefore need their own current limiting resistor.<\/li><\/ul><\/li><li>Making the key caps. The keys themselves can be 3D-printed in two parts, with black surrounds and a transparent center. But the challenge is still how to make the \u201cmask\u201d at the top surface nicely.<ul><li>My current plan is to print the numbers and letters as outlines (clear text, black background) on two pieces of transparency sheets glued together \u2026 similar to how I did the annunciators on the overhead panel, but this is messy and tricky to do neatly<\/li><\/ul><\/li><\/ul>\n\n\n<p><img decoding=\"async\" src=\"https:\/\/blog.shahada.abubakar.net\/wp-content\/uploads\/2017\/10\/20171016_004457-scaled.jpg\" width=\"100%\"><\/p>\n\n\n<p><em>Originally created with EverNote at 20171015T164045Z<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>I found these push button switches have a built-in LED in the center. Looks like it is time to revisit the 737FMC project, this time with Version 3 featuring backlit buttons? The yellow version&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":8543,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[211],"tags":[],"class_list":["post-8387","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-737-fmc"],"_links":{"self":[{"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/posts\/8387","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8387"}],"version-history":[{"count":5,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/posts\/8387\/revisions"}],"predecessor-version":[{"id":9011,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/posts\/8387\/revisions\/9011"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=\/wp\/v2\/media\/8543"}],"wp:attachment":[{"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8387"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8387"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.shahada.abubakar.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8387"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}