zking786

Not high enough to power a bulb, but high enough to cause the transistors to tick. Must be a capacitor that could have blown or been damaged. Could this cause the resistors to heat up?

Will try that test and get back to you. What would you clasify as "high impedence"? Would 10 ohm do? BTW, when I have the transformer hooked up to the circuit, I do hear oscillation. There's a soft ticking noise from the transistors. When I disconnect the transformer, the ticking noise stops, though. Is this what you were talking about?

What's odd is all my tinkering must have done something to one of the tantalum capacitors. Now, if I plug the circuit in (with the correct resistors), I get about 12VAC out of the transformer (instead of 120VAC). If I do a DC test on the capacitors, I get one charging to about 17.5V and the other to 2.5V. Is it blown, or gradually deteriorating?

Definitely Tantalum. I have everything on the circuit. I tried the 200 ohm (219 to be exact) resistors and I got significantly less AC voltage. I have purchased 2160 ohm 1W resistors to hook up in parallel and these should get me closer to 180 ohms. I'm wondering whether the power rating on these is high enough, though. If I analyzing the circuit, I find that i=I(219)/(219+2160) where: i=the current drawn from the branch with the 2160 ohm resistor I=the current entering the branch (of both the 2160 ohm and the 200 ohm) Since the resistor is 1W, then should 1=i^2*(2160) ? What do you think of this modification? Should it allow me to draw more current? When a circuit like this outputs less power, could it be the resistors that are limiting it? Or would they just heat up and explode?

No advice?

I'm thinking of putting on better resistors. Maybe 180 ohm, 5W and 10 ohm 10W. I don't think it could hurt to increase the power the resistors can handle. Also, I have recently purchased and setup heatsinks for each of the transistors. How do you know the max power is 115W, though. Wouldn't it be 12V x 15A = 180W? When I hooked up the 100W soldering iron, it didn't even light up. The circuit did, however, draw about 4A from the 12V battery. Wouldn't it be able to draw 15A before skimping out? Any idea why the iron didn't heat? Also, will 200 ohm, 10W resistors do if I can't find the 180ohm ones? (This is, of course, assuming you recommend increasing the power rating of the resistors.)

I have finally gotten the inverter to work. It seems that there was a minor wiring error. I'm not completely sure what was wrong, since I had everything wired correctly, but when I resoldered a couple of wires (which still had solid connectivity), it worked. Maybe it must have been a minute resistance error? Anyway, there's a new problem . The described circuit is meant to handle 300W, but it seems way to weak. I've tried a laptop charger plug (nearly 90-100W) and it barely powers it. When I connect a 100W soldering iron, it doesn't even heat. Why? Also, I notice the resistors seem to heat up pretty quickly. Sometimes it's the small 180 ohm, 1W resistors, other times (and more rarely) it's the 10 ohm, 5W resistors. I'm wondering why, and whether I should replace these with higher power rated resistors. I've fused the battery-circuit line at 7.5A and the fuse hasn't blown, so it can't be drawing too much current. If I'm not mistaken, the transistors (and the whole circuit) should be able to handle 15A current draw. Any idea what's the problem? For reference, here's the site for the original schematics: http://www.aaroncake.net/circuits/inverter.htm

You would need to search google for a table of refractive indeces. I think there are some materials with a refractive index of over 4, but am not sure of the names.

Isn't the TIP30 series PNP and not NPN? I redid the whole circuit and it still doesn't work. Prior to installing each component, I checked its functionality. The transistors work (BE and BC diodes work), the capacitors charge when I plug them into a low voltage power source (1.5V AA battery), and the resistors all show the necessary voltages when hooked to a multimeter. What could be wrong? This time I even measured wire lengths of the wires I soldered to make connections. Three things I was concerned about include: 1. The diode tests I conducted to ascertain the functionality of the transistors seemed to pass for both diodes, though I got differing diode test values for the transistors at the BC and BE junctions. For the BC junctions I get diode values of 521 and 596; for the BE junctions I get diode values of 475 and 576. 2. I got both transistors from the same place, though, they seem to be labeled differently. One says 2N3055E and the other says CDIL and then 2N3055. Are these fundamentally different? I searched the net and can't find much info on the 2N3055E. 3. Though the capacitors both charge to the same voltage when connected to a AA battery, is this really a good test for functionality? Could they still be blown?

Maybe if I use a high rpm motor at good gearing I could charge the capacitor quickly and more efficiently by brushing the contacts. Or, I could use the oscillator technique. Would I hook the oscilator to the ground and to the base junction of the proper transistor. The collector I'd connect the voltage source and the emitter the induction coil port.

I've been brushing the terminals. Also, I'm wondering how small inductors, like those in the camera's circuit, can so quickly charge a capacitor? Are they using some sort of oscilator or transistor switch? Also, what's "back EMF"?

Are the diodes placed correctly in the described circuit? Interestingly, now I won't get any AC voltage (at either end). The resistors (10 ohm, 5W) seem to take turns heating up (when I plug in the circuit one of the resistors gets really hot, then when I disconnect it and plug it in again, the other might get hot). This time I used all new components. Any ideas why it's no longer working? I've tested the transistors and they aren't blown, the resistors show the correct resistance values, the capacitors are new. What could be wrong?

I see the spark! But it charges really slowly -- I have to tap it about 20 times to get about 5V from a 1.5V battery. I'm afraid I'd blow the 12V lead-acid ups battery I have if I used it.

I used all new parts to set it up (and put in the diodes) with TIP35C transistors instead of the 2N3005 ones. It won't work (no AC voltage generated). Interestingly, this time, one of the lower power resistors (180 ohms) got a bit warm this time. This circuit is really confusing me! Is there a cheaper alternative to the tantalums, that can still work in a 300W circuit? The tantalums are starting to get expensive.

Before I get too excited, actually I already did , it seems something is amiss. When using a voltmeter to test each of the output ends to the center tap, I initially found about ~26VAC. The right bank worked perfectly and sustained a constant voltage. The left, however, didin't. It gradually declined from 26V to 15V, when I heard a slight pop (I'm not sure if it was from the circuit, though). It's important to note, that the circuit continues to output 15VAC consistantly, now, from that bank (hasn't stopped outputing current). The capacitors were only a bit warm, the transistors weren't even a bit warm, but one of the resistors was BURNING hot. The rubber casing seemed to be melting again. This resistor was the one diagonally opposite the terminal which was giving a lower voltage. What does this mean? Should I replace the capacitor or the resistor? What's going on?

I've done that, I've connected the two thin wires into the circuit. In fact, the inductors I'm working with only have two leads. They just seem to be coils wrapped around plastic or rubber posts. There isn't a center tap.

Wow! It works!!!! When I don't have it hooked to the transformer (without the diodes, as you indicated), it puts out ~23V when I test one of the terminals to the center tap using a voltmeter. It must have been the capacitors. Why did you have me remove the diodes? Should I put them back in? Assuming my transformer can handle 300W, can I use this circuit without the diodes to generate 300W?

Once from the camera circuit itself another from a router (about twice the size). I don't know the exact inductance.

The resistance is 1.3 ohms. I definitely won't be able to find a resistor with a low enough resistance. Also, what do you mean by the 1k resistors? The resistors of the circuit are for 10 ohms and 180 ohms. Which ones should I replace and with what resistors?

Hopefully this is the right thread Wouldn't it have blown the capacitor if the polarities were reversed? Earlier, you mentioned that tantalums are really sensitive when it comes to polarity. Also, I was reading your explanation about how the astable multivibrator works and didn't completely understand it. Firstly, why is it that when one transistor is off the other turns on. Secondly, why aren't both capacitors charged at the same time?

The above post is intended to be for another thread. Disregard it. For this thread: I have the circuit set up as prescribed, but no luck. The inductor does warm up, but the capacitor doesn't charge beyond about 0.8V. Why? I've used two different inductors and two different capacitors--same results. Nothing blows, but no substantial voltage buildup.

Wouldn't it have blown the capacitor if the polarities were reversed? Earlier, you mentioned that tantalums are really sensitive when it comes to polarity. Also, I was reading your explanation about how the astable multivibrator works and didn't completely understand it. Firstly, why is it that when one transistor is off the other turns on. Secondly, why aren't both capacitors charged at the same time?

Also, it might be important to note that a website I've seen is telling me that the circuit, itself, is flawed and won't work. I've even been told that the capacitors should be switched in direction to work. Interestingly, I've blown transistors only (I didn't hear any 'pop' from the transistors or the diodes, as a matter of fact, not even the transistors). Anyway, any analysis you can provide will be helpful. Thanks!

So I put an induction coil in series with the capacitor and then disconnect the battery, making sure to close the circuit? How big an induction coil do I need to charge it to 100uF?

I'm very sorry for the delay. I couldn't find a memory stick and had to use a phone's camera. Will work on getting better pictures if these are inadequete.