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  1. hevans1944

    Explain why DMM reads 00.0 on negative side of circuit

    If the resistance is a LOT less than expected, then suspect a short or (in your case) misplaced probes. Martin, I think your explanation was just fine. What we have here with @stspringer is a demonstration of the GIGO principle: Garbage In, Garbage Out. And it has been going on for quite some...
  2. hevans1944

    Phototransistor

    All the texts that I studied from are fifty or more years old. You need to find something apropos to the 21st Century! The theory hasn't changed much, but the practical implementation has. The Internet is one of the best tools available to find what you need to study. One of the best sites on...
  3. hevans1944

    Phototransistor

    I think you will find solid state electronics theory both interesting and gratifying. Briefly, the photo-transistor effect is caused by the creation of electron/hole pairs by the absorption of photons in a semiconductor junction. Each photon can create on electron/hole pair, but not all absorbed...
  4. hevans1944

    Terminal Block to LED Leads

    The connector you ordered and received should work! It appears to me, from way over here and not where you are, that the LEDs you have purchased (maybe el-cheapo Chinese parts?) have leads that are out of tolerance specs... some being too large to fit into the VCC connector, and perhaps others...
  5. hevans1944

    Phototransistor

    This is plotted on non-linear scales in Figure 4 for both the illumination intensity and the resulting collector current as a function of that intensity. In your initial post you stated: How do you expect to perform any calculations when you don't know the theory of how a photo-transistor...
  6. hevans1944

    Phototransistor

    Read the information provided in the datasheet, particularly the information shown in Figure 4 "Collector Current" which plots collector current as a function of illumination intensity. I have no idea what you mean by "gain ratio" but this figure should help you calculate the output current as...
  7. hevans1944

    HV Rat Killer

    One can always hope. It usually takes months before his kind leave the forums. Go back and read his previous posts. It is quite apparent that this guy knows nothing about electronics or electronic design. An engineer? Not bloody likely, but maybe they handed those degrees out like gum-drops...
  8. hevans1944

    HV Rat Killer

    Instead of coming here, where most of us enjoy peaceful pursuits such as lighting strings of LEDs in our spare time, why not use Google to direct you to all sorts of electrical mayhem involving mice, rodents, and maybe even elephants if you can find a link to how Thomas Alva Edison (famous...
  9. hevans1944

    Terminal Block to LED Leads

    Did you check the polarity of the connections to the LEDs? Well, of course you did! This is a mechanical problem is it not? For how many of the green LEDs does your header identified as "2.2.2" actually "sit down properly on the LED leads?" Is it just the one LED that you show that seated...
  10. hevans1944

    Fixed interval Jacob's Ladder?

    You go ahead and acquire the neon sign transformer and someone here will help you wire it up. It would of course be better if you could find a friend in Great Britain who could hold your hand to guide you through the assembly process, but we will do our best to help you once we know what we have...
  11. hevans1944

    Fixed interval Jacob's Ladder?

    @Lol999, the devices you are considering are cheap toys, not transformers, per se. They produce very short, not very intense arcs, that may make for a disappointing Jacob's Ladder display. They consist of a driver oscillator for the primary of a resonant fly-back type transformer whose secondary...
  12. hevans1944

    Fixed interval Jacob's Ladder?

    @Lol999, based on your answers it is obvious that you know nothing about high-voltage arcs. I suggest you do some more research. It is a good idea to enclose the ladder electrodes with some sort of transparent cover to control air convection and ensure a stable, rising, arc. This may also offer...
  13. hevans1944

    Fixed interval Jacob's Ladder?

    I set my 17,500 VAC current-limited neon sign transformer (NST) in a window for Halloween. It runs off 120 VAC, 60 Hz. I usually scrounge up a pair of steel coat-hanger wires for Jacobs Ladder electrodes, which attach to "door-knob" insulated HV terminals located on opposite ends of the...
  14. hevans1944

    Isolation Transformer?

    And to prevent propagating further misunderstanding, could we just close this thread without banning @SailingHome at this time? Mebbe later, 'cause I don't think he is one of us... Need to see some more dialog from him in a new thread to be sure.
  15. hevans1944

    Laser detecting plate

    Not sure what z-axis "information" you expect to extract from your IR image. Most IR lasers will cause the image to "bloom" above a certain power level, and this pretty much destroys any x-y information by smearing the IR pixel out over several hundred adjacent pixels. We used to use a special...
  16. hevans1944

    Isolation Transformer?

    I was in my thirties before I went to work for an employer enlightened enough to see the value of an isolation transformer on my lab bench. Before then, I used two 6.3 VAC filament windings connected back-to-back on a pair of discarded TV transformers to obtain galvanic isolation on my lab bench...
  17. hevans1944

    Isolation Transformer?

    Maybe you are looking in all the wrong places. Try visiting some of the sites that this Google results page brings up. It might help if you told us where (in the world) you are located. You will also need to provide some more specifications for your isolation transformer. Things like VA...
  18. hevans1944

    Fixed interval Jacob's Ladder?

    Sure, it's appropriate, but we need some information from you first in order for the correct circuit is to be retrieved. First, how many volts will you use for your Jacob's Ladder? What is the maximum arc length you anticipate between the electrodes? How will you initiate the initial arc that...
  19. hevans1944

    Heathkit ET 3400

    So how do either of you "beg to differ" with what I posted? This thread was initially about the discovery of an obsolete trainer in very good to excellent condition. It was used in the previous century during the decade of the 1970s to learn about the obsolete Motorola 6800 8-bit microprocessor...
  20. hevans1944

    Laser detecting plate

    In the mid-1960s I was working at the Air Force Weapons Laboratory in Albuquerque, NM trying to build a Shrack-Hartmann Plate wavefront analyzer for infrared weapons-grade lasers. This required sampling the output laser beam with a beam sampler, sending the sampled beam to the wavefront...
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