{"id":922,"date":"2016-11-27T17:21:29","date_gmt":"2016-11-27T16:21:29","guid":{"rendered":"http:\/\/axotron.se\/blog\/?p=922"},"modified":"2016-11-27T17:27:38","modified_gmt":"2016-11-27T16:27:38","slug":"reviving-a-dead-mains-timer","status":"publish","type":"post","link":"https:\/\/axotron.se\/blog\/reviving-a-dead-mains-timer\/","title":{"rendered":"Reviving a Dead Mains Timer"},"content":{"rendered":"

It is that time of year when one puts electric advent stars and candlesticks in the windows. I usually use timers to control them, but this year I ran into a problem. Some of my timers were of the type “EverFlourish EMT757A”, probably bought at Clas Ohlson:<\/p>\n

\"Back<\/a>
Back side of timer<\/figcaption><\/figure>\n

Despite having a notoriously bad user interface (that forces me to google the user manual each time I want to use them), the timers, that had been laying in a drawer since last season, showed an entirely blank LCD display, even when connected to a mains outlet. I guessed that an internal battery just need to be charged, so I left them connected for a day to allow them to be charged up. The display however remained blank.<\/p>\n

Hmm. I had encountered similar timers before that needed the internal battery to be replaced, so I decided to have a look inside to determine if this was the case again. It turned out that the screws used to keep the units together had tamper proof tri-wing heads. Fortunately, I happened to have bits that fit this kind of head, so this did not deter me.<\/p>\n

\"Tri-wing<\/a>
Tamper proof tri-wing screw head<\/figcaption><\/figure>\n
\"Tri-wing<\/a>
Tri-wing bit<\/figcaption><\/figure>\n

I found that there was indeed a tiny chargeable NiMH battery inside the unit (the green component with white corrosion on the side, close to the center of the picture below). Despite the unwanted corrosion, I found that the battery was actually charged to 1.3 V or thereabout, which is fine for a NiMH battery. Maybe it did not need to be replaced after all?<\/p>\n

\"Opened<\/a>
Opened mains timer<\/figcaption><\/figure>\n

But why then was the display dead?<\/p>\n

I put the timer back together again and had another look at the front. Pressing any of the normal buttons did not result in any reaction, but there was also a tiny little recessed button marked RESET. I used a pen to press it and voil\u00e0! The display came to life!<\/p>\n

\"The<\/a>
The timer has been brought back to life.<\/figcaption><\/figure>\n

Stupid me to not try this before I disassembled the unit.<\/p>\n

I suppose the reason the timer behaves like this is that the processor controlling the display probably does not have a proper power on reset circuit. So when the supply voltage is ramped very slowly, as it is when it is powered from a battery that is trickle charged from a state of being completely dead, the processor does not jump into action properly, even after the supply voltage reaches its proper level.<\/p>\n","protected":false},"excerpt":{"rendered":"

It is that time of year when one puts electric advent stars and candlesticks in the windows. I usually use timers to control them, but this year I ran into a problem. Some of my timers were of the type “EverFlourish EMT757A”, probably bought at Clas Ohlson: Despite having a notoriously bad user interface (that … Continue reading Reviving a Dead Mains Timer<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-922","post","type-post","status-publish","format-standard","hentry","category-electronics"],"_links":{"self":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/922","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/comments?post=922"}],"version-history":[{"count":6,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/922\/revisions"}],"predecessor-version":[{"id":931,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/posts\/922\/revisions\/931"}],"wp:attachment":[{"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/media?parent=922"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/categories?post=922"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/axotron.se\/blog\/wp-json\/wp\/v2\/tags?post=922"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}