{"id":6769,"date":"2013-03-19T15:24:53","date_gmt":"2013-03-19T22:24:53","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=6769"},"modified":"2013-03-20T18:25:28","modified_gmt":"2013-03-21T01:25:28","slug":"2013-03-19-tbd","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=6769","title":{"rendered":"2013-03-19 Two Transistor V Boost “JT” Using SMT Inductor"},"content":{"rendered":"

I got some SMT power inductors from dipmicro.com<\/a> because I read that they were only 0.18 ohm and could handle almost 2 amps.\u00a0 The winding is on a ferrite bobbin and that is covered by a ferrite sleeve to give it a better magnetic path.\u00a0 But there is still an air gap between the bobbin and sleeve, which supposedly helps to store more energy (see here<\/a> and scroll down to Applications).\u00a0 They are sealed in epoxy and have two metal ‘feet’ that are soldered to the PC board pads (no holes are needed).\u00a0 I had to solder two leads to them to connect it to my tack soldered circuit.<\/p>\n

\"\"<\/a>This is a standard two transistor PNP-NPN type V boost circuit often mistakenly called a Joule Thief.\u00a0 I decided to use this circuit as a test circuit to try the different inductors I have purchased recently (see Note at end).\u00a0 This circuit had previously run on the yellow-white iron core toroids I had blogged earlier<\/a>.\u00a0 I got better results – higher LED current – with this SMT inductor.\u00a0 I started with a 1000 pF capacitor but I found that the 100 pF capacitor gave more current.\u00a0 I also started with 68k, then added the 50k trimmer pot to adjust the base bias, and found that it had a broad peak that was a bit above 100k.\u00a0 Apparently the base bias controls the circuit in a way that gives a peak to the LED current.<\/p>\n

The BD433 is a power transistor with a plastic case that is totally insulated – there is no metal for contact with a heat sink.\u00a0 It seems to work very well at 1.5V and high current.\u00a0 It must have been switching quickly on and off since there was no sign of it getting warm.\u00a0 I think I could put a 1k resistor from base to emitter (I’ve seen this circuit often with the resistor) and it may help a bit, without wasting much current.<\/p>\n

Back to experimenting…<\/p>\n

Note:\u00a0 I’ve been experimenting to define a standard V boost circuit that uses commonly available parts\u00a0 and will give a well defined performance if the experimenter sticks to the parts list.\u00a0 I guess one could say it will be the next best thing to buying the circuit in kit form.\u00a0 In this case I wanted to drive a white or blue 1 watt or more LED with a 1.5V cell, to where it will put out at least a half watt, but\u00a0 somewhat adjustable by the builder.<\/p>\n","protected":false},"excerpt":{"rendered":"

I got some SMT power inductors from dipmicro.com because I read that they were only 0.18 ohm and could handle almost 2 amps.\u00a0 The winding is on a ferrite bobbin and that is covered by a ferrite sleeve to give it a better magnetic path.\u00a0 But there is still an air gap between the bobbin <\/p>\n

(Read More…)<\/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],"tags":[],"class_list":["post-6769","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\/6769","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=6769"}],"version-history":[{"count":15,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6769\/revisions"}],"predecessor-version":[{"id":6773,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6769\/revisions\/6773"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6769"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6769"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6769"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}