{"id":904,"date":"2012-01-23T10:59:56","date_gmt":"2012-01-23T18:59:56","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=904"},"modified":"2012-03-14T18:54:47","modified_gmt":"2012-03-15T01:54:47","slug":"2012-01-23","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=904","title":{"rendered":"2012-01-23 Watson&#8217;s Tiny Toroid Joule Thief"},"content":{"rendered":"<p><a href=\"http:\/\/rustybolt.info\/wordpress\/?attachment_id=921\" rel=\"attachment wp-att-921\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright size-medium wp-image-921\" title=\"DSCN1888S2\" src=\"http:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/01\/DSCN1888S2-300x223.gif\" alt=\"\" width=\"300\" height=\"223\" srcset=\"https:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/01\/DSCN1888S2-300x223.gif 300w, https:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/01\/DSCN1888S2.gif 706w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a>These <a href=\"http:\/\/www.surplussales.com\/Inductors\/FerToro\/FerToro-3.html\">tiny T231212T toroids from Surplussales.com<\/a> are high permeability so it doesn&#8217;t take much wire to make a good Joule Thief coil.\u00a0 The core is less than a quarter inch diameter (<a href=\"http:\/\/www.cmi-ferrite.com\/data\/toroids.pdf\">here is a data sheet in .PDF<\/a>.). Six inches of 30 AWG magnet wire trifilar wound, with two of the windings connected in parallel for the primary winding.<\/p>\n<p>The transistor is a BC337-25. I put a 2.2 ohm resistor in series with the circuit to measure the battery current.\u00a0 It can be put there temporarily and removed when the LED current is what you want.\u00a0 How do you change the LED current?\u00a0 Change the 1k resistor to a different value.\u00a0 Higher values will reduce the LED current.\u00a0 With the BC337-25 and 1k resistor, the LED current should be close to 20 milliamps so it&#8217;s probably not wise to go much below 1k.\u00a0 If you use another transistor, especially the pipsqueak 2N3904, you may have a hard time getting it to put out 20 milliamps.<\/p>\n<p>Back to experimenting&#8230;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>These tiny T231212T toroids from Surplussales.com are high permeability so it doesn&#8217;t take much wire to make a good Joule Thief coil.\u00a0 The core is less than a quarter inch diameter (here is a data sheet in .PDF.). Six inches of 30 AWG magnet wire trifilar wound, with two of the windings connected in parallel<a href=\"https:\/\/rustybolt.info\/wordpress\/?p=904\"> <\/p>\n<p> (Read More&#8230;)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-904","post","type-post","status-publish","format-standard","hentry","category-joule-thief-smps-dc-dc"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/904","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=904"}],"version-history":[{"count":23,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/904\/revisions"}],"predecessor-version":[{"id":1537,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/904\/revisions\/1537"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}