{"id":6459,"date":"2025-09-07T12:00:00","date_gmt":"2025-09-07T11:00:00","guid":{"rendered":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?p=6459"},"modified":"2025-09-08T11:02:23","modified_gmt":"2025-09-08T10:02:23","slug":"outbuildings-home-automation-light-switches","status":"publish","type":"post","link":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?p=6459","title":{"rendered":"Outbuildings &#8211; Home Automation &#8211; Light Switches"},"content":{"rendered":"\n<p>The Outbuildings are getting a &#8216;light-touch&#8217; Home Automation solution &#8211; compared with the House &#8211; which has dimmable LED lights connected to DALI-controlled dimmable drivers. None of the lights need to be dimmable so they&#8217;re all wired back to KNX-controlled 230V relay banks. (As it happens, some of the light fittings will be Philips <a href=\"https:\/\/www.lighting.philips.co.uk\/consumer\/choose-a-bulb\/sceneswitch\" target=\"_blank\" rel=\"noreferrer noopener\">SceneSwitch<\/a> enabled, providing the option to dim them in 3 stages by switching on-and-off quickly &#8211; and then they remember the setting for next time.)<\/p>\n\n\n\n<p>The question then is how to control these lighting relays:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The small rooms (Plant Room and Shower Room) suit automated presence detection, with PIR sensors connected directly to the KNX bus<\/li>\n\n\n\n<li>All of the lights will be individually controllable via a Smartphone app (e.g. Home Assistant)<\/li>\n\n\n\n<li>There&#8217;s plenty of scope for using inputs from the garage door openers, CCTV cameras or the alarm system to automatically switch lights on and off\n<ul class=\"wp-block-list\">\n<li>For example, all of the external doors will have alarm sensors and these could be configured to switch on the lights in the relevant room (even if the alarm isn&#8217;t &#8216;armed&#8217;)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>It&#8217;s still sensible to provide a wall-mounted light switch in most rooms, so the lights can be turned on and off near the entrance doors.<\/li>\n<\/ul>\n\n\n\n<p>As with some of the rooms in the House, the &#8216;light switches&#8217; are momentary-action switches wired to a low-voltage &#8216;binary input&#8217; sensor bank &#8211; an <a href=\"https:\/\/www.mdt.uk\/products\/product-detail\/sensors\/binary-inputs\/binary-inputs-be.html\" target=\"_blank\" rel=\"noreferrer noopener\">MDT BE16000<\/a> that used to be in the House but was replaced by a smaller unit, specifically to free up the 16-channel unit for the Outbuildings. The &#8216;binary input&#8217; module sends 12V down one of the wires then constantly watches for this appearing on the monitored inputs. For such a low voltage the cabling doesn&#8217;t need to be highly insulated (or to carry a high current) &#8211; but there are some long runs (up to 50m) so a fairly low resistance is preferable. I opted to use 4-core &#8216;alarm&#8217; cable, being careful to choose Copper (rather than Copper Coated Aluminium) conductors<sup data-fn=\"8c597296-f46a-4939-ad5a-7b49ccb354e8\" class=\"fn\"><a href=\"#8c597296-f46a-4939-ad5a-7b49ccb354e8\" id=\"8c597296-f46a-4939-ad5a-7b49ccb354e8-link\">1<\/a><\/sup>. Each of the 4 cores is 0.22mm<sup>2<\/sup> stranded cable and since only two cores are required these are doubled-up. I always use crimped ferrule ends when terminating any stranded cable and two 0.22mm<sup>2<\/sup> cores fit nicely into a 0.5mm<sup>2<\/sup> ferrule. The &#8217;12V&#8217; connections at the Binary Input module are shared between two monitored channels so these have four 0.22mm<sup>2<\/sup> cores in a 0.75mm<sup>2<\/sup> ferrule.<\/p>\n\n\n\n<p>The switches themselves are MK Retractive Grid Module Switches (K4885P WHI) which fit into the MK Grid System frames and Metalclad Plus surface-mount boxes. Some reviews for these switches complain they&#8217;re incredibly hard to press, but I&#8217;ve not found that to be the case at all: they&#8217;re the same as the Logic Plus (white plastic faceplate) switches in the House.<\/p>\n\n\n\n<figure class=\"wp-block-gallery has-nested-images columns-default is-cropped wp-block-gallery-2 is-layout-flex wp-block-gallery-is-layout-flex\">\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"1024\" data-id=\"6460\" src=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-768x1024.jpeg\" alt=\"\" class=\"wp-image-6460\" srcset=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-768x1024.jpeg 768w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-225x300.jpeg 225w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-1152x1536.jpeg 1152w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-1536x2048.jpeg 1536w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2153-scaled.jpeg 1920w\" sizes=\"auto, (max-width: 768px) 100vw, 768px\" \/><figcaption class=\"wp-element-caption\">Light switch cabling terminated at &#8216;Binary Input&#8217; sensor  bank<\/figcaption><\/figure>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"768\" height=\"1024\" data-id=\"6461\" src=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-768x1024.jpeg\" alt=\"\" class=\"wp-image-6461\" srcset=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-768x1024.jpeg 768w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-225x300.jpeg 225w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-1152x1536.jpeg 1152w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-1536x2048.jpeg 1536w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2151-scaled.jpeg 1920w\" sizes=\"auto, (max-width: 768px) 100vw, 768px\" \/><figcaption class=\"wp-element-caption\">Cabling connected to light switch modules<\/figcaption><\/figure>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"768\" data-id=\"6462\" src=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-1024x768.jpeg\" alt=\"\" class=\"wp-image-6462\" srcset=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-1024x768.jpeg 1024w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-300x225.jpeg 300w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-768x576.jpeg 768w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-1536x1152.jpeg 1536w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-2048x1536.jpeg 2048w, https:\/\/www.marshflattsfarm.org.uk\/wordpress\/wp-content\/uploads\/2025\/09\/IMG_2150-400x300.jpeg 400w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">Completed twin light switch (wired from behind)<\/figcaption><\/figure>\n<\/figure>\n\n\n\n<p>Since the &#8216;alarm&#8217; cable isn&#8217;t rated for mains voltage it can&#8217;t share conduit with 230V cabling so is installed in its own conduit &#8211; though in some cases this is shared with the cabling for the alarm system.<\/p>\n\n\n<ol class=\"wp-block-footnotes\"><li id=\"8c597296-f46a-4939-ad5a-7b49ccb354e8\">The House used &#8216;KNX&#8217; cable for this purpose &#8211; <em>specifically<\/em> to allow the selective upgrading of these momentary-action &#8216;dumb&#8217; switches to fully-fledged KNX switches, which has been done for 6 of the switches in the House &#8211; which is why the 16-channel Binary Input module in the House could be downgraded to an 8-channel unit. KNX cable is a lot more expensive than &#8216;alarm&#8217; cable though &#8211; and should never be required for the Outbuildings. (If any of the switches does need swapping for a &#8216;native&#8217; KNX switch in the future, it would be easy enough to pull a KNX cable into the conduit.) <a href=\"#8c597296-f46a-4939-ad5a-7b49ccb354e8-link\" aria-label=\"Jump to footnote reference 1\">\u21a9\ufe0e<\/a><\/li><\/ol>","protected":false},"excerpt":{"rendered":"<p>The Outbuildings are getting a &#8216;light-touch&#8217; Home Automation solution &#8211; compared with the House &#8211; which has dimmable LED lights connected to DALI-controlled dimmable drivers. None of the lights need to be dimmable so they&#8217;re all wired back to KNX-controlled &hellip; <a href=\"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/?p=6459\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"[{\"content\":\"The House used 'KNX' cable for this purpose - <em>specifically<\/em> to allow the selective upgrading of these momentary-action 'dumb' switches to fully-fledged KNX switches, which has been done for 6 of the switches in the House - which is why the 16-channel Binary Input module in the House could be downgraded to an 8-channel unit. KNX cable is a lot more expensive than 'alarm' cable though - and should never be required for the Outbuildings. (If any of the switches does need swapping for a 'native' KNX switch in the future, it would be easy enough to pull a KNX cable into the conduit.)\",\"id\":\"8c597296-f46a-4939-ad5a-7b49ccb354e8\"}]"},"categories":[23,14],"tags":[],"class_list":["post-6459","post","type-post","status-publish","format-standard","hentry","category-build-progress","category-home-automation"],"_links":{"self":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6459","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6459"}],"version-history":[{"count":2,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6459\/revisions"}],"predecessor-version":[{"id":6465,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6459\/revisions\/6465"}],"wp:attachment":[{"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6459"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6459"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.marshflattsfarm.org.uk\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6459"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}