{"id":8220,"date":"2013-08-08T16:54:55","date_gmt":"2013-08-08T23:54:55","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=8220"},"modified":"2013-08-30T00:50:13","modified_gmt":"2013-08-30T07:50:13","slug":"2013-08-08","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=8220","title":{"rendered":"2013-08-08 EMP Blog Uses Watson’s Supercharged JT"},"content":{"rendered":"

I came across this guy’s EMP blog<\/strong><\/a> describing his experiments with various Joule Thiefs, and the results he got.\u00a0 I couldn’t find an email address or how to contact him, so right now I just have to say it in my blog.\u00a0 He has been methodical and taken measurements while he has experimented and he shows the graphs of his results.<\/p>\n

He has done some research, and viewed some Joule Thief info online, one of them was my blog.\u00a0 I’m proud to say that he thought highly of my Supercharged Joule Thief.\u00a0 But I was concerned\u00a0 that he might damage something when he said that the transistor was overheating when he used three cells: the battery voltage was higher than the LED voltage.<\/p>\n

When experimenting with Joule Thiefs, there are a few things that are important to remember.\u00a0 One is that the LED is connected almost directly to the battery.\u00a0 The resistance of the coil’s primary winding is very low, less than 1 ohm typically.\u00a0 One end is connected to the battery, the other end to the LED, so it is almost the same as a direct connection to the battery.\u00a0 The blue or white LED’s forward voltage is about 3.2 volts. \u00a0 If the battery voltage is increased to 3V, the LED will start conducting, even with\u00a0 the transistor disconnected.\u00a0 This means the battery voltage is too high.<\/p>\n

Two fresh alkaline cells in series will give 3.1 to 3.2 volts, which will light the LED very brightly.\u00a0 Two used alkaline cells at 1.4V each will give about 2.8V, which should light the LED dimly, and may work okay.\u00a0 Or two NiMH or NiCd rechargeable cells at 1.4V maximum each will give 2.8V or less, and should work okay.\u00a0 If the LED still lights when the base of the transistor is disconnected, then the voltage is probably too high.<\/p>\n

Another item that is important is the maximum negative voltage on the base, which is 5V or 6V\u00a0 for most silicon transistors.\u00a0 The emitter to base junction of most silicon transistors will start to break down at about 7 to 10V, and acts like a Zener diode.\u00a0 But this permanently damages the transistor, the current gain will be permanently lowered.<\/p>\n

Also, as the higher voltage causes current to flow in the LED, the LED’s resistance goes down, which loads the rest of the circuit, and prevents the transistor from switching on and off.\u00a0 Instead, the current through the1k resistor just turns the transistor on and it gets hot from excessive current.<\/p>\n

Emitter To Base Breakdown<\/p>\n

The voltage across the feedback (base) winding is the same as the voltage across the primary (collector) winding, but it is negative, and the battery voltage, typically 1.5V, is subtracted from it.\u00a0 So if there are\u00a0 two LEDs in series, the total peak voltage across them is typically 4 to 4.5 volts each, or a total of 8 to 9V.\u00a0 Subtract 1.5V, and it’s 6.5 to 7.5 volts.\u00a0 This is more than the 5 to 6V maximum rating, and may damage the transistor.<\/p>\n

This indicates that it’s a bad idea to put two or more LED in series; instead the LEDs should be put in parallel.\u00a0 If the LEDs must be put in series, then the number of turns on the feedback winding should be reduced.\u00a0 Half as many turns means half the voltage.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

I came across this guy’s EMP blog describing his experiments with various Joule Thiefs, and the results he got.\u00a0 I couldn’t find an email address or how to contact him, so right now I just have to say it in my blog.\u00a0 He has been methodical and taken measurements while he has experimented and he <\/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-8220","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\/8220","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=8220"}],"version-history":[{"count":9,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/8220\/revisions"}],"predecessor-version":[{"id":8430,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/8220\/revisions\/8430"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8220"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8220"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8220"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}