{"id":2561,"date":"2012-05-04T07:42:18","date_gmt":"2012-05-04T14:42:18","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=2561"},"modified":"2012-09-21T08:54:07","modified_gmt":"2012-09-21T15:54:07","slug":"2012-05-04","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=2561","title":{"rendered":"2012-05-04 11 LED Lights From An Inverter!"},"content":{"rendered":"

\"\"<\/a>Holy Smokes!\u00a0 Peanutbutter291’s experiment<\/strong><\/a> (Youtube vid) has gone to extremes!\u00a0 There must be way over a hundred dollars in the 11 LED lights, not to mention the socket to outlet adapters, power strip and 3-way taps, which must add up to another $40 to $50.\u00a0 I was at the Big Box store this evening and noticed an inverter for thirty bucks or so.\u00a0 This one plugged into the car’s cig lighter socket and put out a hundred watts at 120VAC.\u00a0 This got me to thinking when I saw his video.\u00a0 He could have saved over a hundred dollars and many hours of his time by buying one of these inverters and plugging his LED lights into it.\u00a0 And he would still have plenty of power left over for when he needs to heat up his soldering iron.\u00a0 Isn’t it crazy?\u00a0 How much trouble we go to to get an experiment running, when there’s a lot simpler solution at the store.<\/p>\n

Schematic<\/strong>\u00a0 His comment gives a link to the schematic by lasersaber<\/a>.\u00a0 He calls this a “Super Joule Ringer 2.0” but I have no idea why he calls it a “ringer.”\u00a0 The same high voltage winding that is used to drive the light is used to drive the base of the transistor.\u00a0 The problem with this is that the reverse voltage on the base causes the emitter to base junction to break down like a zener, and this damages the transistor.\u00a0 In order to prevent this, there should be protection connected across the base and emitter pins.\u00a0 That’s easy and simple.\u00a0 Connect two 3.3 volt zener diodes in series, with the end with the black band connected together.\u00a0 Then connect the remaining ends to the emitter and base.\u00a0 When the reverse voltage goes up to about 4 volts, the zener diodes conduct and prevent excessive voltage on the base.\u00a0 Why two zeners?\u00a0 Because a single zener with the cathode or band end connected to the emitter will prevent excessive reverse voltage.\u00a0 But when the forward voltage appears across the base to emitter, and also across the zener, the zener will conduct and shunt the current away from the base.\u00a0 Adding the second zener diode prevents this.<\/p>\n

Another way to do this is to put 3 or 4 regular diodes in series. and connect the lead with the cathode or banded end to the base.\u00a0 When the reverse voltage gets up to 1.8 volts or more, the diodes will conduct and protect the base against breakdown.\u00a0 For moderate currents at higher frequencies, use 1N4148 diodes, or for higher currents at audio frequencies, use 1N4003 type 1 amp rectifier diodes.\u00a0 I added the protection to his schematic and I’m attaching it here.\u00a0 If lasersaber wants to add the picture to his site, and wishes to contact me to have this removed, he can email my yahoo.com address, acmefixer.<\/p>\n

\"\"<\/a>The cost of a few diodes or zeners is a few cents, so to my thinking, the choice is obvious.\u00a0 In the case where the experimenter still wants to use this circuit without protection against E-B reverse breakdown, I have a solution.\u00a0 I’ll sell you a carton of a hundred new (old stock) 2N3055 transistors (see the picture), and then you can just remove the “used up” one and put a new one in whenever you need to.\u00a0\u00a0 \u03a9<\/p>\n

Update May 5<\/strong><\/p>\n

Peanutbutter replied to my comment:
\n@acmefixer1<\/span> The circuit is similar, but WITH a base bias resistor as shown in Improvements part 1. Yes, the circuit as shown is “hard” on a transistor, though current won’t back flow until VBceo is exceeded in reverse. In some cases a TVS, zener, or diode can be used; yes. However, in many cases this will STOP and prevent oscillation. So, protection via a positive bias allow oscillation AND prevents reverse current flow.<\/p><\/blockquote>\n

I don’t accept “the circuit is hard on a transistor…”.\u00a0 What is happening is the circuit is missing protection against reverse breakdown of the emitter to base junction.\u00a0 I’ve built the “Slayer Exciter” circuit which is very similar, and it uses a LED from base to emitter to protect against reverse breakdown.\u00a0 The reverse breakdown protection cannot “STOP and prevent oscillation” because it is an open circuit and does not conduct during normal oscillation.\u00a0 Only when the reverse voltage becomes excessive does it conduct and prevent reverse breakdown.<\/p>\n

The addition of “positive bias” does not provide protection against reverse breakdown.\u00a0 It does not “prevent reverse current flow”.\u00a0 It is very easy to demonstrate how the current flows in the base lead.\u00a0 Connect two red LEDs in parallel so that the cathode or lead with the flat spot of one LED is connected to the anode (no flat spot) of the other LED.\u00a0 Disconnect the lead to the base and connect it to one pair of LED wires, and connect the remaining pair to the base, so now the two LEDs are in series with the base.\u00a0 Power up the circuit.\u00a0 If the circuit is not causing reverse breakdown of the base, there will only be a single LED lit, which shows that the base current is flowing only in the forward direction.\u00a0 If both LEDs light up, then there is current flowing in the forward and reverse directions, and the base to emitter junction is breaking down in the reverse direction.<\/p>\n

Any circuit design that intentionally subjects its components to destructive conditions is not a design, it’s stupidity, and the designer is not learning from his previous bad experience that there is a design deficiency.\u00a0 Unfortunately disaster will follow if the design is not changed, and he\/she deserves the consequences.<\/p>\n

Someone might wonder why I have a whole carton of a hundred 2N3055 transistors lying around in my workshop.\u00a0 Well, long ago, before I understood why my circuits would blow out power transistors, I had the opportunity to obtain a whole ‘brick’ of them for a very good price. So I took advantage of that opportunity.\u00a0 Then I learned about how to prevent them from being damaged.\u00a0 Ever since, my use (or abuse) of 2N3055s has dropped drastically, and I found that I really don’t need them as ‘spares’ any more.<\/p>\n

Back to experimenting…<\/p>\n","protected":false},"excerpt":{"rendered":"

Holy Smokes!\u00a0 Peanutbutter291’s experiment (Youtube vid) has gone to extremes!\u00a0 There must be way over a hundred dollars in the 11 LED lights, not to mention the socket to outlet adapters, power strip and 3-way taps, which must add up to another $40 to $50.\u00a0 I was at the Big Box store this evening and <\/p>\n

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