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  1. hevans1944

    Common Cathode Triple digit display pinmap help!!!

    Sometimes you luck out and these displays will fit the pin spacing on a solderless breadboard. If so, plug it in so you have access to the pins and the front of the display simultaneously.
  2. hevans1944

    Van de Graaff Generator

    Yeah, it's really hard to hold off corona discharges in air. Making the sphere larger helps "smooth out" the electrical field. The larger columns are needed to support the weight of the moving belt or chain. When these things were first invented, they sometimes built two of them with opposite...
  3. hevans1944

    Cup with heat awareness

    Many years ago you could purchase liquid crystal thermometers that consisted of a row of liquid crystal dots, each dot changing color over a narrow temperature range. I still have several of these that work over ambient temperature ranges, but I am pretty sure they can be made to cover the hot...
  4. hevans1944

    Common Cathode Triple digit display pinmap help!!!

    What a crock. From your fuzzy out-of-focus picture it appears there are only 28 pins on the package connecting to 24 segments, including a decimal point for each digit, plus a common cathode for each digit. So, out of 28 pins, 27 are actually used. However, there are many more than 1000...
  5. hevans1944

    logging current over a 24 hour minimum period

    Here is a bench type multimeter with 4-1/2 digits resolution, 4000 mA DC current range, RS-232 computer interface, free software, and a $200 price tag. Not saying this satisfies all your requirements, but it does measure up to 4000 mA with 1 mA resolution at one second intervals. You can...
  6. hevans1944

    Van de Graaff Generator

    It depends on where your losses are occurring, and whether you have a "serious" Van de Graaf generator or just a "toy" good mainly for making hair stand on end. In theory, as long as the charge collecting sphere is accumulating charge, and the charge does not "leak off," there is no limit to...
  7. hevans1944

    series parallel RC circuit help

    Yeah, lazy editing strikes again. This type of phrasing is common in physics problem texts. It is used as a clue here to mean the capacitors are not part of the steady-state analysis. Once the student realizes that, the "problem" devolves to finding the voltages developed across three resistors...
  8. hevans1944

    series parallel RC circuit help

    Capacitors that are "fully charged" (whatever that means) in a steady-state DC circuit are not conducting current. They can therefore be removed from the steady-state analysis as @Colin Mitchell stated in Post #2. Follow his instructions to find the potentials across all the resistors and hence...
  9. hevans1944

    Length measurement

    Nice try, @bigone5500. Your suggestion has caused me to rethink this problem. The cable diameter varies as @Abhishek Bansal explained in post #4 above, and according to him that creates a problem: He doesn't explain why the wire diameter is varying... perhaps it has something to do with how the...
  10. hevans1944

    Length measurement

    I can think of two other approaches that could work. The first (and easiest) is to make the wheel over which you pull the cable, and whose revolution you count, really large. Ten meters diameter maybe. Then small variations in cable diameter will have less effect on the measurement. The second...
  11. hevans1944

    Material For Touch Screen

    Go to this page and see if anything there will give your some ideas.
  12. hevans1944

    broken 100w resistor - can i use it?

    Well, I guess you will just have to hope the glue on the tape will hold after the resistor gets hot. If the tape fails, try @bigone5500 suggestion to glop some JB Weld around the resistor. I can testify this epoxy is really good stuff.
  13. hevans1944

    208/240V Transformer

    It would probably be more effective on the secondary, installed in the same case as the thermostat. If installed in the primary at the transformer, you need a fuse in the hot lead that will blow if the MOV shorts failed. It might be difficult to find an MOV with a low enough "trip" voltage to be...
  14. hevans1944

    logging current over a 24 hour minimum period

    Welcome to Electronics Point! Do you have a budget? What interval do you want to record current readings? "As frequently as possible" is not a specification. Specify samples per second, or samples per minute, or samples per hour, or samples per fortnight. Specify the rate at which you want to...
  15. hevans1944

    broken 100w resistor - can i use it?

    Welcome to Electronics Point! If you work quickly, you should be able to use super-glue (cyanoacrylate based adhesive) to mate and bond the two pieces together. Apply to both surfaces. Try for an alignment that mates the two pieces seamlessly. Clamp firmly and let dry overnight. Success of this...
  16. hevans1944

    Length measurement

    If you are manufacturing the cables, perhaps you can measure the length with a pair of spring-loaded rollers with a revolution counter attached to one roller. Just place the wire between the rollers and pull the wire, winding it up on a spool perhaps. Such a device is available commercially, but...
  17. hevans1944

    208/240V Transformer

    Well, it is what it is. I hate electric heat. Natural gas is for heat; electric is for light (as Tesla and Edison intended). Yeah, measure the transformer voltage under load with everything energized and working properly. Another possibility is transients on the electric power lines caused by...
  18. hevans1944

    Ferrite's

    Where did you get the information that "you want to select the highest impeadance for the frequency you are working in?" Did you visit the Fair-Rite web site and read and understand their technical explanations? It can be a bit intimidating for a beginner, but it is a good place to start. You...
  19. hevans1944

    208/240V Transformer

    Interesting that your condo is wired for 208 instead of 240 distribution. The 208 is a common phase-to-phase voltage for a three-phase wye distribution because it yields 120 from any of the three phases to neutral. The 240 is a common single-phase center-tapped "pole pig" distribution because it...
  20. hevans1944

    Ferrite's

    It's complicated. Ferrites vary in their properties according to their composition, so there is no "one size fits all" for noise suppression. A good source of technical information is the Fair-Rite web site.
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