Small Transistor CFL table candle

[crob227]

what kind of scope is that???

i got 150 to spend and i need some suggestions.

[Lidmotor]

It is a IWATSU. It was a gift. It is a very good but very old. Go to Ebay and look for something a little less exotic.

[Drevtoobe]

Hi Lidmotor, about that waveform. I will assume that it is the voltage from the second transistor's collector to ground. So when it is high the no current is being pulled through the ignition coil primary, and as it goes down, current starts to flow. I hope that you eventually get a second probe. A neat trick would be to wrap a few turns of wire around the tube of the CFL and use it as a current sensing probe, sort of like the sensor coil for a Bedini motor.

[Drevtoobe]

When the CFL starts to fire, the sudden rush of current through the tube will produce a voltage spike in the sensor coil. Likewise, when the CFL burn ends, the sudden stoppage of current will produce the opposite spike in the coil. The interesting thing would be to look at the timing of the transistor circuit relative to when the CFL burn starts and stops. You could also put a 1-ohm current sensing resistor in series with the CFL itself to tell you amount of current thru the CFL for the burn.

[Drevtoobe]

Rethinking what I just said, all that you need is one scope probe on the transistor collector, and the other scope probe on the 1-ohm resistor in series with the CFL. That tells you the start and stop time for the burn relative to the transistor waveform, and it tells you the magnitude of the current during the burn, quite a bit of information.

A final anal comment: I think you have your scope beam intensity set too bright, risking burning the phosphor in the scope CRT tube.

[Drevtoobe]

The beam intensity adjustment for the scope is there for when you set the time base to a very very fast sweep. The faster the time base sweep, typically the dimmer the waveform on the screen, hence the beam intensity adjustment. When the time base is slower, and the beam intensity is very high, you are bombarding the CRT phosphor with too many high energy electrons and reducing the life of the phosphor coating on the inside of the cathode ray tube.

[Drevtoobe]

Anal comment number two: (lol) All of these self-oscillating circuits that everybody is playing with are fun but bogus. The reason different brands of transistors behave differently is because the transistors are being run outside of their normal operating range, and hence their behaviour is unpredictable. The self-oscillators have almost no stability and that's why the frequency changes when you touch something. Finally, you have no control over the oscillator waveform which sucks big time.

[Lidmotor]

Ok--I will turn the scope brightness way down. In my latest Darlinton experiment I am trying to get away from the uncontrolled self oscillation by putting bias on the first 2n2222 and getting a steady trigger signal from the coil casing. I already have tried the wrap of wire around the CFL and know what that does. That was back in my "Blue Plate Special" days. LOL

[Lidmotor]

Yes the system in the video is running on 4.5 vdc at 20ma. Later on I tuned it a little better and moved the voltage up to 5 vdc at 20ma. As of this posting the light has been running non-stop and it is going into it's third days on that little AA battery pack. Not much light but with that kind of run time I can now go back and work on brightness---spend a few more joules for more lumens.