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  1. hevans1944

    110v to 230v auto switching regulator

    I believe that is correct, based on this specification from the Roland MV-8000 Owner Manual: AC 115 V, 117 V, 220 V, 230 V, 240 V (50/60 Hz)
  2. hevans1944

    Christmas Gift for my 15 year old electronics enthusiast

    One of the best gifts you can give your 15 year old is a dedicated place to work, his own "electronics lab" if you will, where projects will not be disturbed by siblings or others while he is away. A corner bench in his bedroom, or a separate room in the attic or basement, but it is essential...
  3. hevans1944

    Need help finding the right cap

    Well, it IS a breadboard, right? Just solder on some lead extensions. But you probably already figured that out.
  4. hevans1944

    Transformer/Coil

    I am going to wait until @Kavin completes his experiments next week before offering any more comments. A hand on the oscilloscope probe is worth three pages of comments IMHO. BTW @duke37, @Kavin wants sinusoidal excitation to avoid harmonic interference with associated microprocessor logic...
  5. hevans1944

    Transformer/Coil

    I think you are free to pick whatever voltage you want. It all depends on the turns ratio of the transformer. That stub may be a high-voltage insulated trigger electrode (if it is a conductor), but I don't see why the transformer would have so many "extra" wires if it is just a trigger...
  6. hevans1944

    Transformer/Coil

    Those values seem to be on the low side except for a very small flash lamp such as you might find in a disposable camera. Take a look at this link for some typical photography flash lamps, capacitors, transformers, etc. I have no idea where the web site originates, perhaps Japan or Taiwan, but...
  7. hevans1944

    Transformer/Coil

    I have no informed opinion on this because you have not provided sufficient information, some of which i realize you may not have yet. For example, what calculations did you perform to determine that 10 to 14 A are sufficient to shorten the recharging time to an acceptable time period? As they...
  8. hevans1944

    Resistive Load and Battery Life

    No, the heat comes from the amperage flowing through a resistance thus dissipating power: P = I² R You can circulate large currents in superconducting wire coils without any power dissipation because the R term in the equation is zero. Similarly, the largest resistance in the world dissipates no...
  9. hevans1944

    Resistive Load and Battery Life

    For a given rated operating voltage, a higher wattage light bulb will have less resistance than a lower wattage light bulb. The higher wattage light bulb will also exhibit increased amperage, due to its lower resistance, than the lower wattage light bulb. Both situations, lower resistance and...
  10. hevans1944

    Resistive Load and Battery Life

    Just goes to show that intuition will often fail you. "Increasing the resistive load in a circuit" could have two interpretations. Increasing the load could mean you are demanding more power from the battery, similar to adding the weight a weight-lifter lifts, increasing their load. This means...
  11. hevans1944

    Transformer/Coil

    Your reasoning is correct about using transformers "backwards" from their original intent. However, this only applies under steady-state conditions. A flash-lamp power supply does not draw power continuously. Once the capacitor bank is charged, and before the lamp is triggered to discharge the...
  12. hevans1944

    Distressed Nerd - How to increase Motor RPM?

    Yeah, I'll admit I am a fan-boy for variable autotransformers. I have collected a few over the years, both manual as well as stepper motor driven. Thinking about it, this proclivity for such things probably goes way back to my first Lionel train set, which used a variable autotransformer to...
  13. hevans1944

    Shadow signal

    Let me think about this. I have seen such waveforms from biological muscle stimulators, both as you describe as well as polarized. We used these on dissected frog legs back in the day, part of a university heart research program. Don't even ask why frog legs should be applicable to this type of...
  14. hevans1944

    power supply design help

    Since your transformer has a center-tapped 12-0-12 V AC secondary, and you only need 5 V at 100 mA output, I would use a two-diode full-wave bridge rectifier to lower the raw DC voltage to about 16 V. That means only 11 V is dropped across the regulator, dissipating about 1.1 watts at 100 mA...
  15. hevans1944

    LVDT circuit - need to explain how it works

    In Circuit Diagram Part 1 the two rectifier circuits are actually full-wave rectifiers. Consider the circuit that uses IC4C: for both positive and negative signals from the LVDT secondaries, the signal is applied through a 20 kΩ "summing" resistor to the inverting input of IC4B, which has a 100...
  16. hevans1944

    Why is relay latching? :(

    Are the LEDs in the switches illuminated all the time? Do they extinguish when the switch is depressed? I like the idea that @duke37 had of adding some extra load across the relay coil. Please let us know if that worked.
  17. hevans1944

    Why is relay latching? :(

    Try looking in the home alarm section of Lowes or Home Depot or Sears Hardware or Handyman Ace Hardware for a two-part window switch: the kind that has a permanent magnet you mount to one sash and a reed switch that mounts to the other sash. You will have to disassemble the switch part to get at...
  18. hevans1944

    Distressed Nerd - How to increase Motor RPM?

    I agree with @Bluejets solution: just buy a DC fan motor salvaged from an automobile wrecking yard and power it with an adjustable DC power supply. Nothing fancy required: just a step-down transformer, a Variac in the primary, a bridge rectifier in the secondary, and maybe a few thousand...
  19. hevans1944

    Transformer/Coil

    Thank you for that. Now we know we are not having a "conversation" with a rank amateur. I, too, am an electrical engineer with experience in embedded microprocessor control and data acquisition... as well as power electronics and driving "photoflash" devices... among many other things. I don't...
  20. hevans1944

    Phase voltage circuit help

    I like the idea of a three-phase delta to wye transformer, connected to all three phases in parallel with motor and amplifier output. Then with six rectifiers you can get a nice DC signal proportional to all three phases with hardly any ripple. Of course a transformer connected to just two of...
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