{"id":5238,"date":"2012-12-08T07:35:23","date_gmt":"2012-12-08T15:35:23","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=5238"},"modified":"2013-01-09T05:27:23","modified_gmt":"2013-01-09T13:27:23","slug":"2012-12-08-transistor-high-power-jt","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=5238","title":{"rendered":"2012-12-08 2 Transistor High Power &#8220;JT&#8221;"},"content":{"rendered":"<p><a href=\"http:\/\/rustybolt.info\/wordpress\/?attachment_id=5251\" rel=\"attachment wp-att-5251\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright size-medium wp-image-5251\" title=\"DSC_0127S3\" src=\"http:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/12\/DSC_0127S3-229x300.jpg\" alt=\"\" width=\"229\" height=\"300\" srcset=\"https:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/12\/DSC_0127S3-229x300.jpg 229w, https:\/\/rustybolt.info\/wordpress\/wp-content\/uploads\/2012\/12\/DSC_0127S3.jpg 600w\" sizes=\"auto, (max-width: 229px) 100vw, 229px\" \/><\/a>I tack soldered this two transistor &#8220;Joule Thief&#8221; V boost circuit together using one of the 100 microhenry low resistance (0.7 ohm) chokes that I bought from Mouser. I wanted a V boost circuit that put heavy current demands on the choke.<\/p>\n<p>The <a href=\"http:\/\/www.joulethief.com\/kit.php\">schematic for this type of circuit is here<\/a>.\u00a0 I made the following changes.\u00a0 Instead of 470 uH I used 100 uH.\u00a0 The smaller transistor is a BC337-25 and the larger transistor is a BD433.\u00a0 The capacitor is 470 pF and I replaced\u00a0 the capacitor&#8217;s 1k with a jumper (0 ohms).\u00a0 I changed the 2.2k to 22k and connected the upper lead directly to the +1.5V.\u00a0 I changed the 1k (to +1.5V) to a 220 ohm resistor.\u00a0 The LED is a 1\/2 Watt, 10 mm white LED,<\/p>\n<p>With the supply voltage at 1.5V, the supply current was 400 mA and the LED current was 85 milliamps (measured across the two resistors which equal 1 ohm).\u00a0 The frequency was 38 kHz.\u00a0 It&#8217;s capable of handling twice that much, so no strain there.\u00a0 I used a half-dead AA cell to lower the light output while I took the picture &#8211; the LED is very bright on a fresh AA cell.\u00a0 With 400 mA current, the AA cell is not going to last long.\u00a0 It would be better to use a C or D cell, or rechargeable.<\/p>\n<p>Conclusion &#8211; In this two transistor V boost circuit the 100 uH choke puts out some seriously high current to the LED.\u00a0 The Mouser part number is 871-B82144A2104J.<\/p>\n<p>Update Dec 10 &#8211; I removed the 470 pF cap (reddish brown blob) and temporarily replaced it with a 50 to 565 pF variable cap.\u00a0 As I adjusted the capacitor, I found that the LED current fell off as I reduced the capacitance below 470 pF, and there was a broad but distinct peak at 506 pF and the current fell off as the cap increased above 506 pF.\u00a0 The 470 pF that was originally used or a 510 pF are good choices.<\/p>\n<p>Back to experimenting&#8230;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>I tack soldered this two transistor &#8220;Joule Thief&#8221; V boost circuit together using one of the 100 microhenry low resistance (0.7 ohm) chokes that I bought from Mouser. I wanted a V boost circuit that put heavy current demands on the choke. The schematic for this type of circuit is here.\u00a0 I made the following<a href=\"https:\/\/rustybolt.info\/wordpress\/?p=5238\"> <\/p>\n<p> (Read More&#8230;)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,77],"tags":[],"class_list":["post-5238","post","type-post","status-publish","format-standard","hentry","category-joule-thief-smps-dc-dc","category-leds"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/5238","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=5238"}],"version-history":[{"count":17,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/5238\/revisions"}],"predecessor-version":[{"id":5729,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/5238\/revisions\/5729"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5238"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5238"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5238"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}