{"id":5367,"date":"2012-12-19T18:11:47","date_gmt":"2012-12-20T02:11:47","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=5367"},"modified":"2013-05-29T13:59:08","modified_gmt":"2013-05-29T20:59:08","slug":"2012-12-19-power-save-joule-thief-with-c9011","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=5367","title":{"rendered":"2012-12-19 Power Save Joule Thief With C9011"},"content":{"rendered":"

I received a google alert with this Youtube video<\/a> of a Joule Thief which uses a C9011 transistor.\u00a0 The notes give a link to the data sheet<\/a> for this transistor.\u00a0 The actual designation for this transistor is C9011, not<\/span> 2SC9011 (see note at end).\u00a0 As can be seen in the data sheet, the transistor’s absolute maximum collector current is only 40 mA.\u00a0 Also, the Pc is only 400 mW – most transistors can dissipate 625 mW or more.\u00a0 Notice that it says it is meant to be used as a converter and IF amplifier.\u00a0 To me, this means that to get lower capacitance and better RF performance, the makers made the chip and junctions smaller than the typical transistor to reduce Cob for example.\u00a0 That’s another reason why the current and power are lower.<\/p>\n

The typical Joule Thief needs over a hundred milliamps from the battery to give the typical white LED the 20 milliamps that gives true “full brightness”.\u00a0 This C9011 should not be made to go past 40 mA collector current, but it probably is, and very reluctantly.\u00a0 It just can’t do it because the transistor is too small, and if you could hear it talk, it would be screaming and complaining about the current demands.\u00a0 As a result, the circuit is severely limited in its power input and output.<\/p>\n

The video claims that it gives “100% bright[nes]s” with a supply current of only 18 mA.\u00a0 But assuming that it takes about five times as much supply current as the LED current, that means that the LED is getting only 18\/5 or about 3.5 milliamps, which is much less than full brightness.\u00a0 And this assumption that this circuit can put out 1\/5 as much current is probably too optimistic; the actual current is probably even less because the transistor is being pushed far beyond its limits.\u00a0 It is very likely that this circuit is being wasteful and inefficient because of the transistor is unable to handle the higher current.<\/p>\n

The proper way to do this is not by using a wimpy transistor, but by using the proper transistor and changing the base bias resistor to a higher value to get the battery current down to 18 mA.\u00a0 The transistor will then be coasting along and doing a much better job of converting to the higher voltage, with less penalty in efficiency.\u00a0 And the transistor will not be driven past its limits, protecting the circuit against failure.<\/p>\n

Some transistors to use could be the 2N2222A, PN2222A, 2N4401, BC337 or at this lower current, even the 2N3904 or BC547 would do a better job.\u00a0 If you like those C90xx parts, then use the C9012 or C8050, which can handle more current than the BC337.\u00a0 But whatever you use, don’t push the transistor beyond its limits.<\/p>\n

Note: There was a need for a line of transistors for high volume, very low cost use, in very low prices consumer equipment.\u00a0 The line was given the designations of 9011 through 9015 and 8050 and 8550.\u00a0 The numbers are often preceded by a letter such as C or S, depending on the manufacturer.\u00a0 I’ve seen datasheets for them from many companies such as BEL (India), KEC (Korea), and many Japanese companies. \u00a0 These transistors are often found in the low end consumer devices, such as transistor radios.<\/p>\n

Back to experimenting…<\/p>\n

Update May 25, 2013 – I bought a bunch of Fairchild SS9018 VHF transistors, just to make regenerative receivers.\u00a0 These are supposed to be capable of about 700 MHz, 2 or 3 times what the typical 2N3904 can do.\u00a0 Mouser had them for really cheap.<\/p>\n","protected":false},"excerpt":{"rendered":"

I received a google alert with this Youtube video of a Joule Thief which uses a C9011 transistor.\u00a0 The notes give a link to the data sheet for this transistor.\u00a0 The actual designation for this transistor is C9011, not 2SC9011 (see note at end).\u00a0 As can be seen in the data sheet, the transistor’s absolute <\/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-5367","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\/5367","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=5367"}],"version-history":[{"count":18,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/5367\/revisions"}],"predecessor-version":[{"id":5369,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/5367\/revisions\/5369"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}