{"id":2283,"date":"2012-04-16T07:25:14","date_gmt":"2012-04-16T14:25:14","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=2283"},"modified":"2012-04-16T06:24:44","modified_gmt":"2012-04-16T13:24:44","slug":"2012-04-16-stifflers-joule-thief","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=2283","title":{"rendered":"2012-04-16 Stiffler’s Joule Thief"},"content":{"rendered":"

\"\"<\/a>I downloaded Stiffler’s SEC (Spatial Energy Coherence) .PDF<\/a> and I found this schematic on P.47.\u00a0 It’s supposed to be for testing how bright LEDs are with a very short pulse.\u00a0 I found the circuit to be designed for danger; the same high voltage that appears across the primary (collector connected) winding also appears across the feedback winding.\u00a0 And this is connected through the 1k resistor directly to the base of the transistor.\u00a0 When there is a positive 43 volts on the primary winding, there is a corresponding negative 43 volts on the feedback winding – the winding ratios are 1 : 1.\u00a0 The feedback winding is connected to the base without any form of protection against excessive voltage.\u00a0 We know from the datasheets of many transistors that the emitter to base junction is typically rated at a maximum of 5 or 6 volts reverse breakdown voltage, and if this is exceeded, the junction will break down and permanent damage to the transistor will occur.\u00a0 So why does he do this to his transistor?\u00a0 I don’t know.\u00a0 But it should not be done.<\/p>\n

Instead, he should put a white or blue LED from base to emitter, with the cathode or flat spot towards the base.\u00a0 When the base goes negative greater than 3.3V, the LED conducts and the voltage never rises to greater than 3 or 4 volts negative.<\/p>\n

Human eye<\/strong>\u00a0 I don’t agree with Stiffler’s assertion that “The human eye detects peak light levels.”\u00a0 The different wavelengths do different things when they enter the eye.\u00a0 I should say that different wavelengths affect different chemicals, but that may be too simple.\u00a0 In any case, I’m no expert on it and I think it should be left to an expert to say how the human eye responds to light.<\/p>\n

He then uses the term “full brightness.”\u00a0 Well, what is full brightness?\u00a0 He doesn’t define it as being any measured value.\u00a0 And we all know how the human eye tricks us by opening the eye’s iris when the ambient light is dim and closing the iris when the ambient light is bright.\u00a0 This means that the eye is not capable of making a judgment of how bright full brightness is.<\/p>\n

Instead he should go with a definition that is repeatable and measurable.\u00a0 Such as: The LED is at full brightness when there is 20 milliamps DC flowing through it (for a standard 5mm LED), or if the current is pulsed, then the current that is needed to equal the same brightness as 20 milliamps DC.\u00a0 For other size LEDs, instead of 20 milliamps, the current it should be set to is its maximum current.<\/p>\n

I disabled comments due to comment spam.\u00a0 Please send email to my yahoo email address acmefixer.<\/p>\n","protected":false},"excerpt":{"rendered":"

I downloaded Stiffler’s SEC (Spatial Energy Coherence) .PDF and I found this schematic on P.47.\u00a0 It’s supposed to be for testing how bright LEDs are with a very short pulse.\u00a0 I found the circuit to be designed for danger; the same high voltage that appears across the primary (collector connected) winding also appears across the <\/p>\n

(Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,12],"tags":[],"class_list":["post-2283","post","type-post","status-publish","format-standard","hentry","category-joule-thief-smps-dc-dc","category-led"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2283","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2283"}],"version-history":[{"count":26,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2283\/revisions"}],"predecessor-version":[{"id":2286,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/2283\/revisions\/2286"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2283"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2283"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2283"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}