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  1. hevans1944

    "Good" DMMs with bar-graphs - crippled by design?

    Yeah, me too. A logic probe and an oscilloscope are my "go to" tools for that sort of thing. The multimeter is mainly for verifying I remembered to turn the DC power supply on and have connected it to the circuitry. I actually prefer my analog Triplett VOM for continuity measurements because (1)...
  2. hevans1944

    How to control the speed of a 24vdc pump from circulating water temperature?

    @cygnusv and @CDRIVE: I've been lurking here, watching you two make progress on this project, with @Alec_t and @shrtrnd chiming in occasionally. Now that Stu is almost ready for "sea trials" :D I am curious about a few things... my wife and I will be moving to Florida, and one possibility is to...
  3. hevans1944

    Motor Discussion

    Servo (servomechanism): a device that accurately and quickly responds to a command that represents position, velocity, acceleration, angle, or any other physically measurable output. Donkey, please tell us what you are trying to DO!
  4. hevans1944

    Automotive coil on plug conversion HELP

    You cannot distribute the high-voltage output of a single ignition coil except with a gear-driven distributor synchronized to the cam shaft. That is what distributors were designed for. To get four ignition coils, one for each cylinder spark plug, to fire sequentially requires four drivers, one...
  5. hevans1944

    Automotive coil on plug conversion HELP

    Probability of failure is a manufacturing and quality control problem. A 4-coil system should "work real fine, last a long time, cost a little, and do a lot." Recite that mantra to your auto parts supplier and see what they recommend the next time you need a replacement part! The biggest...
  6. hevans1944

    Decade Counter issue.

    Since J-K flip-flops are readily available in various flavors, what is the point in trying to simulate one with discrete logic? Is this a homework problem?
  7. hevans1944

    Rotating tv help

    You need at least three remotes because one will always get misplaced.:(
  8. hevans1944

    help on a RF wireless LED project please

    So, your existing brake lights and turn signals on the motorcycle are not visible enough in traffic and you want to attach to a motorcycle jacket LEDs on the arms and the back and maybe even the front that light up in synchronism with the motorcycle brake and turn signal lights. Is that about...
  9. hevans1944

    Troubleshooting: Why the normally closed and normally open pin in my relay is shorted internally?

    Always read and understand the datasheet for every component in a project before proceeding. From discussion on another thread you started, may we assume the diagram below represents the relay you are trying to use?
  10. hevans1944

    Converting LED to Street Light?

    @Poulostyo Saha: Below is a diagram of the terminal connections for the relay you specified in your post #16. Notice this diagram bears no resemblance to the circuit diagram you posted in post #12 Please draw the circuit you are trying to use by adding connections and devices to the relay shown...
  11. hevans1944

    Polarity diagrams:

    Maybe the image below will help, extracted from this Google result page.
  12. hevans1944

    LED monitor using phototransistor

    And if your project is really strapped for cash, you can pair the red LED with another red LED and use that LED as a photodiode. Do the same with the green LED: pair it with another green LED and use that LED as a photodiode. Using an LED as a photodiode isn't very efficient, but it does work...
  13. hevans1944

    Hantek 5102

    When my new Hantek DSO 5202P gets too confusing, I just swap the test leads over to my ancient Tektronix 465B... losing the waveform storage ability of course. And the math functions. And the USB computer interface. And maybe some brightness of the trace if the sweep speed is very fast. Hmm. I...
  14. hevans1944

    Help building a crossover

    Great! Now go to this page, plug in the speaker impedance (8 ohms, both speakers), and select whichever type of crossover network you want. I would start with the simple Butterworth filter at 2000 Hz (as recommend by the Tweeter datasheet you posted). This uses one capacitor and one inductor.
  15. hevans1944

    LED monitor using phototransistor

    A uv phototransistor may require uv light to operate, depending on what coating (if any) is on the phototransistor entrance aperture. I wouldn't bother going there. Just get a pair of inexpensive visible-light, garden variety, vanilla, phototransistors. Anything you can find online is probably...
  16. hevans1944

    "Good" DMMs with bar-graphs - crippled by design?

    I keep analog multimeters with D'Arsonval movements handy on the bench. I must have used a dozen different types over the years, including the venerable Simpson meters with their taut-band movement and mirrored scale (to avoid parallax errors when reading the pointer position) which I like a lot...
  17. hevans1944

    Hantek 5102

    Simple, you just apply a signal discriminator to the signals in both channels and measure whatever you please.
  18. hevans1944

    Help building a crossover

    The Beyma 12ga50 is a "full musical range" loudspeaker and doesn't require a crossover network. But you didn't specify what Tweeter you are using with this speaker. To protect the Tweeter from low frequencies you can install a small capacitor in series with the Tweeter leads. Try a one...
  19. hevans1944

    Need help identifying electronic!

    I agree with Minder. It looks like an electro-mechanical buzzer, probably an ad hoc door-bell arrangement, probably low-voltage AC operated from a door-bell transformer wired to a push-button switch mounted outside, near the door. Or maybe operated from a 6 V lantern battery. Follow the zip-cord...
  20. hevans1944

    Troubleshooting: Why the normally closed and normally open pin in my relay is shorted internally?

    The N.O and N.C. contacts are normally physically separated by an air-gap with the movable common contact in between. To have continuity between a pair of N.O. and N.C. contacts requires that both the N.O. contact and the N.C. contact be "welded" to the common contact across the air gap! That...
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