{"id":6277,"date":"2013-02-15T18:56:02","date_gmt":"2013-02-16T02:56:02","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=6277"},"modified":"2013-03-16T01:55:40","modified_gmt":"2013-03-16T08:55:40","slug":"2013-02-14-tiny-inverter-transformer-from-goldmine-elec-com","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=6277","title":{"rendered":"2013-02-14 Tiny Inverter Transformer From Goldmine-elec.com"},"content":{"rendered":"

I received the bag of these tiny inverter transformers<\/a> that I ordered from goldmine-elec.com.\u00a0 Each was tiny: 10.7mm wide, 10mm deep, and 9mm high, not counting the leads.\u00a0 There are two windings, the primary which is 0.11 ohms and an unknown inductance, and the secondary which is 48.4 ohms and 350 mH.<\/p>\n

\"\"<\/a>They sent a single page along with the pinout and a schematic of a strobe using this transformer.\u00a0 I redrew the schematic since it was oddly drawn, and I’m going to make some modifications to it.\u00a0 They made some fundamental mistakes that I’m going to correct.\u00a0 The first mistake was to use a TIP126 Darlington transistor for the driver transistor (my earlier blog explains why<\/a>).\u00a0 The supply is only three volts, and .6 volts of that is wasted across the TIP126, as heat – that’s 20 percent!.\u00a0 The first thing to do is get rid of the Darlington.\u00a0 I’m changing it to a BD438 PNP transistor.\u00a0 I will also change the 2N3904 to a PN2222A.\u00a0 Then I have some doubts about the values of R2 and R3.\u00a0 R2 is low for the bias resistor for a small transistor.<\/p>\n

R3 doesn’t seem necessary because the TIP126 has built-in resistors across the base to emitters of both transistors.\u00a0 But since I’m changing it to a BD438, I think it could be lower.\u00a0 It has passed through my thoughts more than once that it looks like the values for R2 and R3 may have been switched.\u00a0 But the 6.5k looks like it should have been 5.6k.\u00a0 I think R3 could be 1k and not waste much power.<\/p>\n

I have changed the R2 to a 10k in series with a 100k pot.\u00a0 I adjusted it to about 10k, so the total R2 is about 20k.\u00a0\u00a0 I changed the C1 capacitor from .005 uF to .001 uF.\u00a0 That blue capacitor can be seen peeking out from under the circuit board.<\/p>\n

The BAV21 or UF4007 is just to reduce the losses from slow reverse recovery of the 1N4007.\u00a0 The C2 and C3 capacitors need 1 meg or 470k resistors to bleed off the high voltage when the circuit is not operating.\u00a0 Also, the resistors would equalize the voltages across C2 and C3.\u00a0 But I am not going to use two capacitors in series, I will use a single 10 uF capacitor, rated at 350 volts.<\/p>\n

\"\"<\/a>I connected two NE-2 pilot lamps in series and connected them across the output as a load.\u00a0 Each lamp has a 33k resistor in series with it.\u00a0 I measured the voltage drop across one 33k at 14 volts, so the current through them is 0.42 milliamps.\u00a0 As can be seen, they light up brightly.\u00a0 The supply current at 3 V was about 200 milliamps.<\/p>\n

Back to experimenting…<\/p>\n

Update – I used this transformer in my blog<\/a> about the “Joule Thief” that is powered by a 40 millivolt thermocouple.<\/p>\n","protected":false},"excerpt":{"rendered":"

I received the bag of these tiny inverter transformers that I ordered from goldmine-elec.com.\u00a0 Each was tiny: 10.7mm wide, 10mm deep, and 9mm high, not counting the leads.\u00a0 There are two windings, the primary which is 0.11 ohms and an unknown inductance, and the secondary which is 48.4 ohms and 350 mH. They sent a <\/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-6277","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\/6277","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=6277"}],"version-history":[{"count":21,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6277\/revisions"}],"predecessor-version":[{"id":6683,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/6277\/revisions\/6683"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6277"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6277"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6277"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}