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  1. hevans1944

    Extremely fast on delay timers?

    There are plenty of circuits available that will block the application of 400 VDC, typically using a MOSFET gated OFF until a "trigger" is received. The trigger, and associated logic, then allows the 400 VDC to be applied to subsequent circuit loads seven milliseconds (0.007s) after the trigger...
  2. hevans1944

    Programable commutator

    I like the idea of using electro-mechanical relays, instead of solid-state switches, for this application. There will only be four relay coils energized at any particular time for a measurement of soil conductivity (or its reciprocal, resistance), with two relay contacts closed on each of two...
  3. hevans1944

    Programable commutator

    It seems to me that what you have here is a multiplicity of earth electrodes, with the requirement to make only two of four possible connections to a particular electrode at any given time: (1) a voltage excitation connection to either the positive or negative power supply terminal and (2) a...
  4. hevans1944

    Tesla coil driver mosfet problems.

    Well, it's been awhile since I last farkled with Tesla coils... I think I left those behind, shortly after the onset of puberty, in favor of more interesting pursuits... and that was waaay before metal-oxide-semiconductor field-effect transistors or MOSFETs were invented. You might be better...
  5. hevans1944

    Tesla coil driver mosfet problems.

    Is there some reason why you have NOT provided a complete and accurate schematic for this thread? How are we supposed to know about that, when you deign it not important enough to include on the schematic? Why did the so-called "Tesla Coil" change from 1:200 turns ratio in your original post...
  6. hevans1944

    Tesla coil driver mosfet problems.

    @Exidor: Are you SURE you posted a correct schematic? The two diodes are forward biased in series across the 60 VDC supply, shorting it out. The transistor emitter has no return path. There may be other problems.
  7. hevans1944

    Response time of device in datasheet help

    So, in your post #1, your blind Google search returned a datasheet for a limited rotation-angle torque-motor/tachometer. You followed this in post #3 with a link to a solenoid valve. There is absolutely no relationship between these two components, other than the manufacturer/distributor...
  8. hevans1944

    Reel to reel machine, new build or Hack?

    True. So remove as much moment-of-inertia as practical from the capstan to allow it to be quickly accelerated and decelerated. Add tachometer feedback to "tighten" the capstan speed control loop. Brute force the damn thing if you have to in order to achieve whatever speed profile you deem...
  9. hevans1944

    Reel to reel machine, new build or Hack?

    I think it is admirable that you would consider both an analog as well as a digital approach. Certainly, given that you want play-back only, and just a variable tape speed for that, the analog approach is simplest. Using a C90 1/4-inch tape cassette may be a viable "reel-to-reel" implementation...
  10. hevans1944

    Reel to reel machine, new build or Hack?

    The playback speed (as well as the record speed) of a "reel-to-reel player" is governed by the rotation speed of its capstan tape drive, in conjunction with a pinch roller that presses the tape against the capstan without slippage between tape and capstan. The only purpose of the reel motors is...
  11. hevans1944

    Wireless signal needed from motorcycle to backpack - don't know how

    There is definitely a possible, even probable, problem with two or more transmitters operating simultaneously. The problem is receiver front-end overload from nearby additional transmitters. When this happens, nothing intelligent makes it through the interference. As an amateur radio operator...
  12. hevans1944

    Wireless signal needed from motorcycle to backpack - don't know how

    Firstly, you need a PLAN before committing to building anything. It would be a good idea to start off with a BLOCK DIAGRAM that abstractly represents what you are trying to DO. The block diagram can start out as a simple box outline with various gazintas (inputs) and gazoutas (outputs). Each of...
  13. hevans1944

    Digital C-ESR meter

    Lots of good electronics coming from the Russian Federation now.
  14. hevans1944

    Dimming an over bright LED

    I would opt for the optical solution: put a dab of ink on the offending puppy.
  15. hevans1944

    AC TO DC with Op amp

    You start by assuming an op amp is a viable solution to the task of converting 230 VAC to 5 V DC. Why would you make such an assumption? If what you are trying to DO is to obtain dual polarity (positive and negative with respect to some common terminal) 5 VDC outputs, then you should NOT begin...
  16. hevans1944

    Frequency response ?

    This would be an example of a total failure of operational security. What organization would go to the trouble of "air gaping" their hardware and then create an open window for the world to look in on? And what kind of op-sec protocols would tolerate the unmonitored presence of thumb drives and...
  17. hevans1944

    Any expert in radio-controlling drones ?

    Point-to-point earth communications are almost trivial, especially if neither transmitter nor the receiver is moving relative to each other. And you are presumably free to select an antenna and a frequency that will make success more certain, as well as a power supply. If for some reason 3 VDC...
  18. hevans1944

    Isolating electric shower

    It would be an expensive solution, but consider installing an "on demand" in-line hot water heater that services only the shower. We live in Florida with our own water well supplying a water softener with aerator tank and a 40 gallon electric water heater. This arrangement services two people...
  19. hevans1944

    Frequency response ?

    Just because something is "dangerous" is no reason to avoid using it. Life itself is dangerous because (last time I looked) there have been NO known survivors. In this electrical/electronics hobby we encounter many dangerous things, for which education and the practice of safety precautions is...
  20. hevans1944

    Frequency response ?

    Absolutely! The first laser diodes were edge emitters, manufactured by cleaving the semiconductor diode wafer material. Not a very bright or spatially coherent source of laser radiation. Lately VCSELs (Vertical Cavity Surface-Emitting Laser) have been developed with much "better" optical...
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