This is a continuation of the 2013 Dec 18 blog.\u00a0 It was getting too long, and so is this blog.<\/p>\n
Update Dec 24<\/strong> – I searched for high current pulse gen schematic using Google and I didn’t come up with anything near enough to what I’m looking for.\u00a0 I saw a lot of high tech and high priced equipment for very specialized applications.\u00a0 I saw some stuff for high voltage generation. \u00a0 I saw only a few schematics and of those only one seemed to be anything close to what I would call simple enough for the average experimenter.\u00a0 That was an avalanche pulse generator<\/a>.\u00a0 And it can’t supply enough power to give the 10 watt LED any kind of brightness.\u00a0 I think my next step will be to go through the books I have and look for something out of the decades when transistors were most popular, like in the 1970s and 80s.\u00a0 Be back soon.<\/p>\n Update Dec 26<\/strong> – Yesterday, during my encounter with some sparkling bubbly stuff [hic], I perused some old books and came up with an old schematic from the ’70s for an emergency auto flasher that uses a 6 volt lamp.\u00a0 I replaced the lamp with the 10 Watt LED and built the circuit on a thin piece of plywood.\u00a0 It uses a PN2222A for Q1 and a TIP32C PNP for the LED driver transistor.\u00a0 Other than that, it’s a typical flasher circuit with two transistors and a 10 uF capacitor that\u00a0 determines the flash rate along with the two base bias resistors.\u00a0 The schematic shows the transistors as being RS-20xx, which are old Radio Shack numbers. Just about any NPN will work for Q1 and any PNP power transistor for Q2, as long as it can handle well over 1 Amp.\u00a0 Alternative types are the BD138 or BD43<\/p>\n It runs down to 9V, but the speed is slow at low voltages and speeds up as the voltage increases.\u00a0 I think that if I put a few k resistor across the LED it might help make it run at lower voltages.\u00a0 I turned the PS’s current control up to maximum, which is 1 amp, but the voltmeter still dips slightly when the flash occurs, which means the power supply is going into current limit mode, so the flasher is drawing over 1 amp peak.\u00a0 The high current pulse is too fast for the current meter to respond, the needle just flicks up a bit.\u00a0 I put a half dozen 10000 uF capacitors across the power input, and a 180 ohm resistor between the caps and the power supply.\u00a0 I adjusted the PS until the voltage across the caps was 10V, and measured the current.\u00a0 Even though there were 60000 microfarads on there, the current still jumped around a bit, but I got a bit under 2.5 milliamps average current.\u00a0 I can safely say that the current is 2.5 mA or less at 10V, which is the maximum rating of the capacitors.<\/p>\n The intensity of the flash is extremely BRIGHT!\u00a0 Like, exceedingly, overwhelmingly bright.\u00a0 I covered the LED with a piece of black electrical tape, and lifted the corner so the flashes came out away from my eyes.\u00a0 They hit the piece of paper on the table and between the flashes the reflection off the paper left a square of dark in my eyes.\u00a0 It’s bright!<\/p>\n Update Dec 27<\/strong> – I took the power flasher along with me to the restaurant to eat with a friend, and I grabbed a 9V battery and some clip leads.\u00a0 I wanted to show my friend how bright it was.\u00a0 I clipped the battery on but it refused to flash.\u00a0 I added the 10000 uF capacitor, and it still refused to flash.\u00a0 Either the battery was low, or the flasher wouldn’t flash on 9V, which was what I found when I tried reducing the power supply voltage down below 10V.<\/p>\n The idea that I came up with was to replace the 9V with one of my 1.5V to 9V DC to DC converters.\u00a0 The converter is perfect for this application.\u00a0 The flasher’s average current is less than 3 mA at about 10V, so that comes to about 30 milliwatts.\u00a0 The typical Joule Thief puts out about 66 mW, and draws about twice that from the single AA cell.\u00a0 So if the converter is about 50% efficient then the current from the battery should be about half of the normal JT current.\u00a0 That means the Joule Thief will easily have plenty of output to run a single power flasher, or even enough to run two of them.<\/p>\n This morning I drew up a schematic of a preliminary circuit.\u00a0 It consists of two sections; the power flasher itself, and the Joule Thief power supply.\u00a0 This afternoon I built up the Joule Thief power supply section.\u00a0 It boosts the voltage to 9.5 to 10.5 volts.\u00a0 It does have a quirk, though.\u00a0 I used a 2200 uF 16V capacitor across the output to act as a reservoir to allow the flasher to draw a very high current for a fraction of a second.\u00a0 When this large cap charges up the JT power supply shuts off and the voltage drops down, then it kicks in again, sort of like an oscillation.\u00a0 I’m going to have to investigate further.<\/p>\n","protected":false},"excerpt":{"rendered":" This is a continuation of the 2013 Dec 18 blog.\u00a0 It was getting too long, and so is this blog. Update Dec 24 – I searched for high current pulse gen schematic using Google and I didn’t come up with anything near enough to what I’m looking for.\u00a0 I saw a lot of high tech <\/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":[142,4,12,13],"tags":[],"class_list":["post-9079","post","type-post","status-publish","format-standard","hentry","category-flashers-and-attention-getters","category-joule-thief-smps-dc-dc","category-led","category-lighting"],"_links":{"self":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9079","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=9079"}],"version-history":[{"count":10,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9079\/revisions"}],"predecessor-version":[{"id":9083,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/9079\/revisions\/9083"}],"wp:attachment":[{"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9079"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9079"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rustybolt.info\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9079"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}