{"id":2425,"date":"2020-11-07T13:50:03","date_gmt":"2020-11-07T12:50:03","guid":{"rendered":"http:\/\/www.dotmana.com\/weblog\/?p=2425"},"modified":"2021-05-05T10:40:24","modified_gmt":"2021-05-05T08:40:24","slug":"led-light-flicker-diy-measure-it","status":"publish","type":"post","link":"http:\/\/www.dotmana.com\/weblog\/2020\/11\/led-light-flicker-diy-measure-it\/","title":{"rendered":"LED light flicker: DIY measure it"},"content":{"rendered":"\n

We all experienced it: light flicker! When concentrating on a piece of work or dead tree text, the light suddenly goes berserk and flash like a stroboscope on the dance-floor.<\/p>\n\n\n\n

After fixing a TV with LED backlight<\/a>, let’s dive in different performance of light fixture\/light bulbs.<\/p>\n\n\n\n

This effect is especially present in LED light fixtures where there is no inertia: incandescent or fluorescent light have a thermal or phosphor inertia and continue to glow a flick of second after the power is cut. But not the LED (even though there is some phosphor in them), this leads to have a close relation of the light intensity and the supply voltage.<\/p>\n\n\n\n

Most of LED light bulb are supplied from main, the quality of the AC\/DC converter takes a main role here. Because good rectification and filtering cost, manufacturer are cutting them, and you get this effect.<\/p>\n\n\n\n

You can find two type of power supply on LED bulbs: simple rectification with LED string to match the AC rectified voltage. Or AC\/DC converter with inductor and constant current control (this is what you want).<\/p>\n\n\n\n

I wanted to “quantify” it, more that just a feeling, but didn’t want to drop hard cash (k\u20ac$ range) for dedicated equipment.<\/p>\n\n\n\n

So I used one of the simplest and cheaper photo sensor on the market: a NPN phototransistor, (not a photoresistance as the bandwith is to small), in addition with a 10k resistor, connected to the GND (ring 2) and MIC (sleeve).<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

Then use a simple Android software, called Oscilloscope<\/a><\/p>\n\n\n\n

\"\"<\/a><\/figure>\n\n\n\n

The result is then very straightforward, especially in spectrum analyzer:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"
Standard office ceilling panels with AC\/DC block converter under the drop down ceiling<\/figcaption><\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
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Ultra cheap LED light bulb COG (chip on glass) with bridge rectifier (4 diodes)<\/figcaption><\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
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100\u20ac\/$ photo studio panel with external AC\/DC power supply or battery operated<\/figcaption><\/figure>\n\n\n\n

I now always have this small 3.5mm 4 ring photo-transistor adapter in my pocket when shopping light bulb\/appliances in home improvement, so I can point it and discard the worst devices.<\/p>\n\n\n\n

If someone comes up with a better idea, to measure more accurately amplitude and ideal the spectrum (would need a dedicated color sensor though), with an easy to use interface, that would be awesome.<\/p>\n","protected":false},"excerpt":{"rendered":"

We all experienced it: light flicker! When concentrating on a piece of work or dead tree text, the light suddenly goes berserk and flash like a stroboscope on the dance-floor. After fixing a TV with LED backlight, let’s dive in … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-2425","post","type-post","status-publish","format-standard","hentry","category-ubuntu"],"_links":{"self":[{"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/posts\/2425","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/comments?post=2425"}],"version-history":[{"count":6,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/posts\/2425\/revisions"}],"predecessor-version":[{"id":2454,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/posts\/2425\/revisions\/2454"}],"wp:attachment":[{"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/media?parent=2425"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/categories?post=2425"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.dotmana.com\/weblog\/wp-json\/wp\/v2\/tags?post=2425"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}