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  1. hevans1944

    BOSCH reputable car battery manufacturer? then where are datasheets?

    Colin, I think they use BA semiconductors mounted on large heat sinks to replace the carbon pile variable resistor.
  2. hevans1944

    Ultrasonic sensor working underwater?

    So why not just mount it above the water and measure the distance to the water surface? That distance will increase as the cistern is emptied.
  3. hevans1944

    5000W high power mosfet

    I have to agree with @dorke's original comment in post #2: you need some more theory and experience under your belt before attempting this project. It is not a trivial task to specify a heat sink. The heat resistance specification you mentioned means that heat sink will rise three degrees...
  4. hevans1944

    2 transistor circuit input output question.

    I want to amend my post #64: both of you are hopelessly pedantic. That's a good thing, right?:D
  5. hevans1944

    Buying soldering iron

    There are two common methods: a thermocouple or a magnetic switch that operates at the Curie temperature. The latter was patented, but I am sure the patent has expired by now. A thermocouple produces a micro-volt signal at soldering temperatures so some signal conditioning is required. There may...
  6. hevans1944

    How to use water proof ultrasonic sensors?

    I looked at the vendor page you linked to, as well as pages for several similar transducers. My conclusion is the "waterproof" transducers are just that: immune to water getting inside and ruining the transducer. IMO these "waterproof" transducers are NOT intended for use under water, they are...
  7. hevans1944

    2 transistor circuit input output question.

    From a practical point of view, Wheatstone bridges are usually used in a nearly balanced configuration (four strain gauges for instance) with a constant-voltage excitation, or an excitation that is sensed at the bridge and used as a reference for the circuitry that processes the bridge...
  8. hevans1944

    How to use water proof ultrasonic sensors?

    You have not told us what the waterproof ultrasonic sensors are: manufacturer's name, model number, datasheet, etc. No solution possible without more information. The non-waterproof sensors are standard crystal transducers used everywhere for distance measurement and intrusion detection in air...
  9. hevans1944

    Ultrasonic sensor working underwater?

    Well, the United States Navy seems to have good luck with them working underwater. And commercial fish finders seem to work okay too. That is where I would look for an inexpensive waterproof sensor. Maybe try to find a small ultrasonic jewelry cleaner with an intact crystal too. Or wind your own...
  10. hevans1944

    Wuuussuuup?

    Welcome to Electronics Point, Marine! (Once a Marine always a Marine!) Thank you for your service. Nate, you have found the right place. I suspect most of us here are born tinkers. Jump in with questions or comments at any time. Plenty of expert and some not-so-expert advice available here for...
  11. hevans1944

    2 transistor circuit input output question.

    I have no idea what that means, but here is a Google link that might help.
  12. hevans1944

    2 transistor circuit input output question.

    Just now checked it. Works for me. Try again.
  13. hevans1944

    Interfacing between Little and Big endian

    Wow, Bob! Not being a programmer, I wasn't aware this compiler existed. Good job extending the life of apps written for the PowerPC to play nicely with the Gorilla in the room (Intel). True. And DEC probably had an inferiority complex vis a vis IBM. Oh, DEC tried hard with the VAX series, but...
  14. hevans1944

    2 transistor circuit input output question.

    Yes, it sure does. But the "Two Sources with Shared Load" problem is the one I most vividly remember: A good tutorial that analyzes both circuits using a variety of methods can be found here.
  15. hevans1944

    12 volt DC lamp flasher.

    Lots of neat ideas on that page. Thanks @(*steve*) !
  16. hevans1944

    Question about DC and Coils and LED.

    Gee, Colin, I haven't tried that yet. How many turns of what size wire on what diameter would you recommend for the coil attached to the battery and the coil attached to the LED? Bifilar wound or two coils some distance apart? Should the OP use a ferromagnetic core to get better coupling? Toroid...
  17. hevans1944

    Question about DC and Coils and LED.

    @revv You are on the right track theory-wise with the battery, two coils, and an LED. Unfortunately, from a practical point of view, the coil connected to the battery will look like a dead-short and will quickly drain the battery. Your two coils are probably not tightly coupled together...
  18. hevans1944

    2 transistor circuit input output question.

    Well, folks, Thevenin Equivalent Circuit is supposed to simplify things... I recall the classic problem of two voltage sources of arbitrary value and polarity, each connected to a series resistor, with the other end of each of those two resistors connected to a third resistor and thence to...
  19. hevans1944

    Complete the circuit!

    @Harald Kapp and @Ratch you didn't mention that a positive phase angle for the current is caused by...
  20. hevans1944

    Limit car battery current

    Sure. I'll even plug and chug the numbers for you: R = 12/41 = 0.29268292682926829268292682926829 Ω How's that for service? Your turn: what are you trying to do? What electronics projects? Please answer @BobK's question (post #5).
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