![\"\"](\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/51\/2018\/12\/IMG_4088.jpg\")
<\/a>When I recovered from my immediate shock, I switched off a couple of things and headed downstairs to restore the power. I found that the upstairs power outlet circuit had tripped and somehow this triggered the RCD that took out the whole house. I switched the circuits back on and various bleeps told me that the house was rebooting. I went back to my office to survey the damage.<\/p>\nWhat actually happened? As yet, I am not 100% certain. Clearly there was a voltage difference – and, from the amount of damage, I would guess that it was the full 240v mains – between the shells of the two plugs. This is obviously not the way it should be! I suspect the USB power outlet. This is a switched mode power supply [SMPS]. As a humble software engineer, I only [think that I] understand the basics. Instead of using a step-down transformer, as we did in the Good Old Days, an SMPS monitors the input AC voltage and taps off some power for a moment each time it reaches the required output voltage. It seems to me that this has lots of potential [sorry, no pun intended!] for things to go wrong. A knowledgeable friend suggested that whoever installed the socket [that was me ?] may have swapped Live and Neutral; this would often not matter, until it does.<\/p>\n What lessons have I learned? Several, I guess:<\/p>\n And with this cautionary tale, may I take the opportunity to offer you the season\u2019s greetings. If you celebrate Christmas, have a good one. And may all of us have a peaceful and prosperous New Year! See you in 2019.<\/p>\n What makes you describe something as \u201cscary\u201d? I guess there are many things. Possibilities include events that are unexpected, sudden,…<\/p>\n","protected":false},"author":71677,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[1],"tags":[302],"industry":[],"product":[],"coauthors":[],"class_list":["post-8858","post","type-post","status-publish","format-standard","hentry","category-news","tag-off-topic"],"_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/posts\/8858","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/users\/71677"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/comments?post=8858"}],"version-history":[{"count":1,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/posts\/8858\/revisions"}],"predecessor-version":[{"id":10748,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/posts\/8858\/revisions\/10748"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/media?parent=8858"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/categories?post=8858"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/tags?post=8858"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/industry?post=8858"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/product?post=8858"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/embedded-software\/wp-json\/wp\/v2\/coauthors?post=8858"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/a>First off, I switched on the iMac, with fingers crossed. It started up just fine. It seems to be quite resilient to power outages and appeared none the worse for the experience. I plugged in the USB hub. It lit up as usual, but when I tried to use a printer, that was plugged into it, the device showed up as \u201coffline\u201d. Plugging it into the computer directly showed that the printer was OK. The hub was clearly a casualty. I nervously checked the USB power outlet [with a Lightening cable] and it appears to be fine. I inspected both micro-USB plugs and the metal outer part of both [where they came into contact] has a part missing and was charred.<\/p>\n\n
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