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  1. hevans1944

    12v DC photocell switch that powers one circuit at day and another at night?

    A SPDT relay with a low-voltage DC coil driven with one or more solar cells (however many are needed to provide sufficient voltage to energize the relay coil) can be used to switch between daytime and nighttime operation. The power source is connected to the moving contact of the relay, the...
  2. hevans1944

    Illuminated DPDT Switch

    That should have worked. Polarity is important for LED illumination: However, if you connected battery negative to the 2b terminal on both switches, it is possible the 12 V battery doesn't provide enough voltage to "light up" the LED. The switch contacts are rated from 14 V DC up to 250 VDC...
  3. hevans1944

    Capacitor charging itself?

    Good point, Bob. But actually it is a 1237.5 μF NOT 1235.7 μF: (3300) (9) / (24) = (3300) (0.375) = 1237.5.
  4. hevans1944

    Capacitor charging itself?

    @Harald Kapp: That "solution" for a 24 V, 3300 μF capacitor is so impractical I didn't even mention it.:eek: But just supposing you could construct such a capacitor with a very thin removable (plastic?) dielectric, you could "charge" it up (or, more correctly, energize it) with 9 V DC and then...
  5. hevans1944

    Capacitor rated voltage question.

    Pretty much agree. Just look at my vanity website to find electrical engineering services advertised as DC to Light™. Anything between one gigahertz and a few terrahertz is just a stepping stone. Lately, almost all the interesting stuff is taking place at infrared wavelengths. At one time, the...
  6. hevans1944

    Polarity reversing smart switch

    Let Google be your friend and search for "cellphone controlled relays" or some similar search string. Lots of products available, some more expensive than others, some with more than one channel of control. Product you select will depend on type of cellphone (CDMA or GSM) and/or whether you want...
  7. hevans1944

    Capacitor rated voltage question.

    Woah! Don't youse guys mix down all that giggle-hertz stuff to real RF wavelengths so your intermediate frequency amplifiers can play? IIRC, my size components can still play a role there. Pretty soon now, all radios will be direct conversion and software defined, so very few discrete components...
  8. hevans1944

    Help with strobes!

    Why build when you can buy? Visit the links on this Google web page result for the search string "emergency vehicle strobe lights." If I were going to design and build a flasher/turn-signal sequencer like you described, I would use a Microchip PIC microcontroller and a couple of logic-level...
  9. hevans1944

    I need help with capacitors...

    Ummm. The original question involved two 1000 μF, not 100 μF, capacitors. But your are right: it is still meaningless. Based on this and similar threads started by the OP, I think they should probably lower their sights quite a bit as to which college they should seek admission after graduating...
  10. hevans1944

    Capacitor charging itself?

    Is English your native language? WTF is a "capacitor witch"? Some sort of paranormal capacitor? How do you (or your teacher) expect to add energy to any capacitor without using a power source? Is this an advanced course in practical magic, or are you actually studying electronics? Please...
  11. hevans1944

    Capacitor rated voltage question.

    It would certainly be inappropriate for tuned RF circuits to use multi-layer ceramic capacitors (MLCC), which have a huge voltage coefficient of capacitance, as resonating elements. I have always used ceramic capacitors for high-frequency by-pass applications, often placing them in parallel with...
  12. hevans1944

    I need help with capacitors...

    100 F = 100,000,000 μF. So, add another 500 μF in parallel with that and you have 100,000,500 μF or 100.0005 F NOT 100.5 F.
  13. hevans1944

    CO2 laser tube lifespan - time used vs age of tube?

    That would probably be a waste of a good laser tube, depending on other factors of course. Does the tube have external resonating cavity mirrors, with windows mounted to the end of the tube at Brewster's angle? If the laser tube is sealed with cavity mirrors permanently mounted... never mind. Is...
  14. hevans1944

    Understanding basic passive components: resistors, capacitors, inductors.

    Thanks, Adam! And Harald, too, of course. Comments and advise appreciated. The problem is sifting through all the information available, both on-line and in my head, and deciding what is appropriate material to throw at a newbie, while still possibly being useful as a reference to others. I...
  15. hevans1944

    Understanding basic passive components: resistors, capacitors, inductors.

    @Harald Kapp, I was going to go back and make "pretty print" after I got my thoughts down on "paper" so to speak. Lots of editing left to do. This "project" was inspired by a new poster from India who asked about capacitors, and to whom I gave a very short answer and a link to hyperphysics...
  16. hevans1944

    Smartphone interfacing with Audio Amplifier and External Speakers.

    Aww! I plan on eventually doing that here at home, but didn't want to confuse the OP, who can add this capability later after he purchases the amplifier and speakers.
  17. hevans1944

    9 way clap switch

    The OP hasn't responded. Could a moderator please close this thread?
  18. hevans1944

    Smartphone interfacing with Audio Amplifier and External Speakers.

    Yes.
  19. hevans1944

    Understanding basic passive components: resistors, capacitors, inductors.

    hevans1944 submitted a new resource: Understanding basic passive components: resistors, capacitors, inductors. - passive electronic components Read more about this resource...
  20. hevans1944

    Attuning Universal Remote to a DVD/VCR device

    Perhaps you can find a replacement remote here.
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