{"id":7643,"date":"2013-06-16T16:11:01","date_gmt":"2013-06-16T23:11:01","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=7643"},"modified":"2013-07-22T05:19:07","modified_gmt":"2013-07-22T12:19:07","slug":"2013-06-16","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=7643","title":{"rendered":"2013-06-16 1.5 to 9V Converter Uses Supercharged Joule Thief PCB"},"content":{"rendered":"

I have built a few dozen of my Supercharged Joule Thief Flashers<\/a> using the PC boards that I designed and had made with ExpressPCB (schematic is in the link above and PCB picture is below).\u00a0 The circuit works okay with a fresh battery but when the battery gets low the light comes on solid, and that happens when the battery is below about 1V.\u00a0 My Blue Blinky does a better job of flashing.\u00a0 So I decided to use one of the SJT Flasher PC boards as a 1.5V to 9V DC-DC converter.<\/p>\n

\"SJT-Flash-2(PCB)\"<\/a>When I designed the board, I added a few traces and holes for the Schottky rectifier ‘SD’ and filter capacitor (no label, just + and -), so the board has the room and is ready to work as a DC-DC converter.\u00a0 However it’s just a single transistor, there is no other transistor to control the base bias of the SJT.\u00a0 So I just removed the jumper ‘1’ and put a Zener diode in series with the blue LED.\u00a0\u00a0 When the voltage gets up to about 8.6V, the LED and Zener conduct and limit the voltage.\u00a0 In other words it’s a shunt regulator that wastes the excess power in the LED and Zener.\u00a0 But because it’s a Supercharged JT, it only draws about 23 mA from the 1.5V supply.<\/p>\n

I used a 1N5817 for the Schottky diode, a 470 uF 10V for the capacitor, and a 5.6V, 1\/2W Zener.\u00a0 The output is taken across the LED and Zener. The transistor was a S8050, and the 4u7 capacitor and 150k were removed and replaced with a single jumper.<\/p>\n

When I put a 3600 ohm load (about 2.2 mA) across\u00a0 the output, the voltage dropped from 8.6 to 8.2V.\u00a0 The supply current remained at 23 mA, — no change.\u00a0 The frequency was\u00a0 about 116 kHz.<\/p>\n

Since this circuit draws a constant 23 mA from the single cell, it’s not a good choice for powering a DMM or other meter that might be left on for several minutes.\u00a0 It would be a good choice for a crystal tester, light meter or Gate Dip Oscillator, which are used for only a short period, maybe less than a minute.\u00a0 There are some gotchas when the circuit is used for a radio.\u00a0 See my earlier blog on powering the superregen receiver.<\/p>\n","protected":false},"excerpt":{"rendered":"

I have built a few dozen of my Supercharged Joule Thief Flashers using the PC boards that I designed and had made with ExpressPCB (schematic is in the link above and PCB picture is below).\u00a0 The circuit works okay with a fresh battery but when the battery gets low the light comes on solid, and <\/p>\n

(Read More…)<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-7643","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\/7643","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=7643"}],"version-history":[{"count":9,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/7643\/revisions"}],"predecessor-version":[{"id":8100,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/7643\/revisions\/8100"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7643"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7643"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7643"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}