Search results

Search Forums New Posts
  1. hevans1944

    Optocoupler symbol?

    It is an opto-coupler. No need for lines to indicate light transfer from the internal LED to the photo-transistor. Does it have a part number? Here is a page with many images of opto-couplers, most with arrows indicating the optical emitter, but some without. The function is obvious from its...
  2. hevans1944

    Where can I buy a 20,000°/sec gyroscope?

    Perhaps you should visit this page and choose something.
  3. hevans1944

    help with ac

    Perhaps you can visit one of the web pages at this link and then tell us what your requirements are.
  4. hevans1944

    Wireless doorbell help

    It appears you have already removed "some components" (the cases) so what more do you wish to DO? And why?
  5. hevans1944

    Questions on LT3080

    Paralleling the outputs of two or more devices requires a low-value "current sharing resistor" in series with each output, recommended to be a short (as in "not long") circuit board trace.
  6. hevans1944

    Replace fried range hood transformer with cheaper alternative?

    Whereas this fine stainless steel oven hood requires two men and a boy to hoist it into place and secure it. So let's save some weight here...
  7. hevans1944

    Questions on LT3080

    Remember, these are functional schematics, not meant to portray the acutal circuitry inside the IC. The Vcontrol is simply the power source for the internal electronics. The "ammeter symbol" is used in lieu of two intersecting circles to represent a current source (saving space on the page)...
  8. hevans1944

    Questions on LT3080

    In the "soft start" circuit, D1 and C2 are the soft start part. C2 charges through the internal current source to provide a soft start. When input power is removed, C2 discharges through D1. In the second circuit, the two devices are in cascade, not paralleled. The first device acts as a...
  9. hevans1944

    Replace fried range hood transformer with cheaper alternative?

    Looks like some of these "electronic transformers" are designed to also serve as dimmers. I guess the range hood manufacturer wanted to try to cover as many bases as possible.
  10. hevans1944

    Replace fried range hood transformer with cheaper alternative?

    And folks wonder why an appliance repair service has to charge upwards of $70 per hour to find and replace a $10 piece of imported junk... electrolytic capacitors mounted over a range hood? They should have used 117 V halogen lamps.
  11. hevans1944

    volume to liter conversion

    You are probably thinking of a frustrum of a right circular cone. Free calculator for volume here.
  12. hevans1944

    Zeroing out a LM317 reference voltage with a zener - PSU build

    It's NOT a diode. It's an analog integrated circuit with two terminals that acts like a zener diode. The LM4041DYM3-1.2-TR appears to be an acceptable substitute for the LT4004-1.2 with a lower recommended reverse operating current of 12 mA maximum. Absolute maximum reverse current is still 20...
  13. hevans1944

    Zeroing out a LM317 reference voltage with a zener - PSU build

    Yikes! You tricked me into launching LTSpice! Okay, so leave D12 in the circuit if it makes it work. I don't see how it does anything other than allow the voltage on C4 to add to the voltage across D13 when the anode of that diode is negative with respect to common. In fact, if you leave D12 in...
  14. hevans1944

    Oscillator or Not?

    Gee, folks... it's only a science fair project. I think we have posted most of the perils and pitfalls associated with this kind of "experiment." Let the science fair judges decide whether the protocol, hypothesis, experimental results, and conclusions are valid research or not. As for the...
  15. hevans1944

    Zeroing out a LM317 reference voltage with a zener - PSU build

    You already have the "1.225 zener" in place on your original schematic post. Now you just have to provide a small negative voltage through a current-limiting resistor to its anode. I think the "-9V" circuit will provide that, but you don't need the voltage multiplication it provides. So, yes...
  16. hevans1944

    Zeroing out a LM317 reference voltage with a zener - PSU build

    @chopnhack: Maybe you don't need an auxiliary transformer after all. I found this "voltage doubler" schematic on another web site forum that @Bluejets linked in his post #2. It was posted by "Hero999" and you have to scroll way down the page to find it: Notice this derives -9V from a...
  17. hevans1944

    Oscillator or Not?

    Where did you get the number 200? It was my understanding that someone else did all the trial-and-error work of constructing and testing "trial" filaments until the "secret sauce" was finally discovered. Edison provided the support staff and laboratory facilities, but did very little of the...
  18. hevans1944

    "Lightpole" Project

    @Herschel Peeler RE: Design 592. Good thing you stated that the counter delay-to-activate circuit can be replaced by a microprocessor. It doesn't work properly "as is" because operation of the toggle switch immediately stops the counter associated with the other switch position, whether the five...
  19. hevans1944

    "Lightpole" Project

    I don't know diddly about Airsoft gaming, but other than some common-sense safety rules, it appears that a "game" can be anything the players want it to be from a "Kill or Be Killed" free-for-all skirmish with last man standing winning, to highly organized "battlefield" operations with dozens or...
  20. hevans1944

    Low tension ignition inductor

    Trevor, my "gut" feeling is you have the dimensions, turns, wire gauge, ID, OD, winding resistance, and battery voltage close to what you need, but the inductance "L (no core) 3.04mH" seems to be way too small, and it does not agree with your calculated energy stored in the magnetic field. If...
Top