{"id":3269,"date":"2012-07-09T13:38:37","date_gmt":"2012-07-09T20:38:37","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=3269"},"modified":"2012-10-21T07:16:28","modified_gmt":"2012-10-21T14:16:28","slug":"2012-07-09-supercharged-joule-thief-reduced-birghtness","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=3269","title":{"rendered":"2012-07-09 Supercharged Joule Thief – Reduced Brightness"},"content":{"rendered":"

\"\"<\/a>Peter is experimenting with my Supercharged Joule thief circuit<\/a>.\u00a0 His picture is one of his recent results: a Supercharged Joule Thief flashlight.\u00a0 I quote:<\/p>\n

Hello and thanks for the fast answer,<\/p>\n

Now I want an SJT as a nightlight cause there are many so called “depleted” batteries lying around – I built one on breadboard with a blue LED but it was too bright!
\nIs there a possibility to regulate or decrease the brightness?<\/p>\n

Of course I give you permission to use this in your blog! At the moment I\u00b4m using two old AA cells in parallel which should give me enough energy for a decent time.
\nI understand the tweak with the resistor but have a question on the capacitor: “Should I measure the current the circuit consumes and choose the one which makes it consume the least?”\u00a0 Is this what you meant?<\/p>\n

Thanks<\/p>\n

Peter<\/p><\/blockquote>\n

Peter:<\/p>\n

Increase the 1.5k resistor to 3.3k, 4.7k, or higher, until you have the desired LED brightness.\u00a0 This may change the optimum point, so the 680pF or whatever capacitor may not be the best choice.\u00a0 The peak of the optimum point is very broad, so adjusting the 680pF may not have a large effect.\u00a0 But I think that it is always a good idea to tune the SJT to save battery current.\u00a0 And that is especially important when you are using button cells.\u00a0 Thanks for the pictures.\u00a0 I haven’t had time to work on my blog, but when I do, I’ll try to update it with your pictures<\/p>\n

I put a 1 ohm resistor in series with the LED cathode.\u00a0 I measure the millivolts across it, and each millivolt is equal to 1 milliamp.\u00a0 Then as the capacitor is changed, the LED current will have a broad peak.\u00a0 I put ten 100 pF disk capacitors in parallel on a PC board with each capacitor connected to one of the switches on a 10\u00a0 position DIP switch.\u00a0 I can then switch on the capacitors so they add up to 1000 pF.\u00a0 For the 1.5k, I’ve found that the capacitor is typically between 560 pF and 1000 pF, depending on the coil and current.\u00a0 Typically the core I use is the Fair-Rite 2673002402 with ten to 12 turns of 24 AWG (0.5mm) wound bifilar.\u00a0 The inductance of each winding is typically above 200 microhenrys.\u00a0 The Supercharged Joule Thief circuit runs at 3 or 4 times the frequency of a typical conventional JT – maybe 200 to 250 kHz.<\/p>\n

More experimenting?\u00a0 Probably.<\/p>\n","protected":false},"excerpt":{"rendered":"

Peter is experimenting with my Supercharged Joule thief circuit.\u00a0 His picture is one of his recent results: a Supercharged Joule Thief flashlight.\u00a0 I quote: Hello and thanks for the fast answer, Now I want an SJT as a nightlight cause there are many so called “depleted” batteries lying around – I built one on breadboard <\/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":[5,4,12,13],"tags":[69,65,45],"class_list":["post-3269","post","type-post","status-publish","format-standard","hentry","category-flashlight","category-joule-thief-smps-dc-dc","category-led","category-lighting","tag-adjustable-capacitor","tag-night-light","tag-supercharged-joule-thief"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3269","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=3269"}],"version-history":[{"count":6,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3269\/revisions"}],"predecessor-version":[{"id":4725,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/3269\/revisions\/4725"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3269"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}