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  1. hevans1944

    Need Help Improving Brightness in Multiplexed 7 Segments (6 Digits)

    Adam, the effect I am talking about occurs because of persistence of vision at low ambient light conditions. It does not appear to be significant in a brightly lit room. I liken it to the same effect you see when you wave a light around in the dark, leaving "streaks" in the path of the light...
  2. hevans1944

    Need Help Improving Brightness in Multiplexed 7 Segments (6 Digits)

    I don't much care for multiplexed LED displays because of "flicker" and the weird effects created by eye and head motion. Many years ago I was tasked with creating a 7x9 (or maybe it was 5x7) dot-matrix LED display with digits about four inches or so high. The vertical column data (derived from...
  3. hevans1944

    Wow...he calls it the Scariac!!

    Yup. And most novices armed with a Variac don't realize that it doesn't work as a speed control for the common induction motor found on most stationary power tools like drill presses and table saws. I have found that a variable AC transformer (Variac) is useful as an incandescent light dimmer on...
  4. hevans1944

    Wow...he calls it the Scariac!!

    I like it! And notice there is no "green wire" safety ground to confuse things up-stream, like a GFI circuit breaker. I wonder if using NaOH + H2O as the electrolyte keeps the copper nice and clean? I have about ten pounds or so of copper sulfate out in the garage... I wonder if that would make...
  5. hevans1944

    Drill bits for homemade PCBs?

    I am talking Transportation Safety Administration (TSA), those friendly folks who keep people from carrying on stuff that might be used as a WMD or worse... provided it isn't carried on in underwear. I've tried to avoid flying since a few buildings came down on September 11, 2001, presumably...
  6. hevans1944

    Please identify this component

    And here is a link... now on SALE for US$545.00! Save US$150.00! Looks like it includes ear hair attachment at no extra cost. No mention of nose hair or eyebrow option though.
  7. hevans1944

    Drill bits for homemade PCBs?

    I kept a box of dull bits at work, hoping to sharpen them eventually. Most of them were large enough to use with a Drill Doctor that has a high-speed diamond cylinder that does a decent job of producing a fine edge. A new hire spotted the box and sent the whole lot out for professional...
  8. hevans1944

    Please identify this component

    Oh, really? How well did that work before the "buzzer" failed? Looks like a lot of circuitry just to grow some hair. Can you post "before" and "after" pictures? Where can we buy one?
  9. hevans1944

    voltage output slowly decreasing by .01 why?

    Not that it's relevant to your "problem" but D1, D2, C1 and C2 form a half-wave voltage doubler; the diodes conduct on alternate half-cycles. Other than that, I agree with everyone else: you are seeing an inconsequential thermal drift. Live with it, or use a more sophisticated design.
  10. hevans1944

    Drill bits for homemade PCBs?

    If you have a technique or tool for sharpening those tiny (sub-millimeter diameter) drill bits, please share! I once worked with a machinist who could sharpen most anything by hand, aided only by his trained and experienced Mark I Eyeball, but I never master that process except maybe for wood...
  11. hevans1944

    Drill bits for homemade PCBs?

    I don't think zealous is the proper description; just practical. The question seems to be: is a carbide drill bit necessary for drilling PCB holes, or will high speed steel (HSS) bits work just fine, cost a little, do a lot, and last a long time? It has been my experience that HSS drill bits...
  12. hevans1944

    Float Switch for 240V pump using a relay

    The first one with an 8-pin octal tube socket is ideal for your purpose. Easy to solder wires onto the tube socket terminals. Your should mount the tube socket inside a protective plastic or metal box, protect the solder connections with shrink tubing. The second one is designed for printed...
  13. hevans1944

    Drill bits for homemade PCBs?

    Somewhere on the web there is guidance on surface speed for carbide tools cutting various materials. However, the general rule-of-thumb is the smaller the bit diameter the higher the RPM required for cutting instead of just heating the tool. Good ol' trial-and-error will usually lead you to the...
  14. hevans1944

    Float Switch for 240V pump using a relay

    From the series of relays you cited, one with a 12 V DC coil would work well with your float switch and a 12 V DC adapter. The coil current requirement is only 0.075 A, well within the current capability of your AC/DC adaptor.
  15. hevans1944

    Homemade DC generator(dynamo) with a spinning coil

    ...and lights a light bulb!
  16. hevans1944

    Float Switch for 240V pump using a relay

    This is the key requirement. You purchased a relay with a coil voltage that is too high. Relay coils come in two flavors: AC and DC. If you are using a step-down transformer to get low-voltage AC from 220 V AC choose a relay with an AC coil that matches the secondary voltage of the transformer...
  17. hevans1944

    Drill bits for homemade PCBs?

    Any wobble or "play" in the spindle will quickly kill a silicon carbide drill bit, which are virtually required for drilling holes in circuit boards. HSS bits will dull after only a few holes are drilled. I am currently attempting to use a Dremel tool mounted in a Dremel "drill press"...
  18. hevans1944

    Homemade DC generator(dynamo) with a spinning coil

    It makes no difference if the magnet is spinning or the coil is spinning, but you still have to do as your short-sighted lecturer says if you want a passing grade. For a real-world example of a "DC current generator (dynamo)" with a spinning magnet look no further than a common automobile...
  19. hevans1944

    Tried my hand at SMD soldering.

    I hope you didn't feel I came down too hard on you for your first SMD soldering attempt. Actually, it wasn't too bad for a first effort. But as others have said the key is practice, practice, practice. You have the right tools, flux and solder. A temperature controlled 60 W soldering iron for...
  20. hevans1944

    Not enough current to trigger relay.

    Hey, guys, I am schematic challenged at the moment. Would someone please post a simple wiring diagram for the OP?
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