Holy Smokes! Peanutbutter291’s experiment (Youtube vid) has gone to extremes! 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. I was at the Big Box store this evening and noticed an inverter for thirty bucks or so. This one plugged into the car’s cig lighter socket and put out a hundred watts at 120VAC. This got me to thinking when I saw his video. 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. And he would still have plenty of power left over for when he needs to heat up his soldering iron. Isn’t it crazy? How much trouble we go to to get an experiment running, when there’s a lot simpler solution at the store.
Schematic His comment gives a link to the schematic by lasersaber. He calls this a “Super Joule Ringer 2.0” but I have no idea why he calls it a “ringer.” The same high voltage winding that is used to drive the light is used to drive the base of the transistor. 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. In order to prevent this, there should be protection connected across the base and emitter pins. That’s easy and simple. Connect two 3.3 volt zener diodes in series, with the end with the black band connected together. Then connect the remaining ends to the emitter and base. When the reverse voltage goes up to about 4 volts, the zener diodes conduct and prevent excessive voltage on the base. Why two zeners? Because a single zener with the cathode or band end connected to the emitter will prevent excessive reverse voltage. 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. Adding the second zener diode prevents this.
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. When the reverse voltage gets up to 1.8 volts or more, the diodes will conduct and protect the base against breakdown. For moderate currents at higher frequencies, use 1N4148 diodes, or for higher currents at audio frequencies, use 1N4003 type 1 amp rectifier diodes. I added the protection to his schematic and I’m attaching it here. 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.
The cost of a few diodes or zeners is a few cents, so to my thinking, the choice is obvious. In the case where the experimenter still wants to use this circuit without protection against E-B reverse breakdown, I have a solution. 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. Ω
Update May 5
Peanutbutter replied to my comment:
@acmefixer1 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.
I don’t accept “the circuit is hard on a transistor…”. What is happening is the circuit is missing protection against reverse breakdown of the emitter to base junction. 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. The reverse breakdown protection cannot “STOP and prevent oscillation” because it is an open circuit and does not conduct during normal oscillation. Only when the reverse voltage becomes excessive does it conduct and prevent reverse breakdown.
The addition of “positive bias” does not provide protection against reverse breakdown. It does not “prevent reverse current flow”. It is very easy to demonstrate how the current flows in the base lead. 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. 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. Power up the circuit. 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. 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.
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. Unfortunately disaster will follow if the design is not changed, and he/she deserves the consequences.
Someone might wonder why I have a whole carton of a hundred 2N3055 transistors lying around in my workshop. 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. Then I learned about how to prevent them from being damaged. 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.
Back to experimenting…
