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  1. CDRIVE

    Help amplifying a tiny current

    The LM393 is open collector logic. This means it can't source current. Because of this your base drive current will be totally dependent upon the value of the pullup resistor connected to "DO". Since the output LED lights when 393's output pin goes low (not high) I would think that you should be...
  2. CDRIVE

    electromagnetism

    This is probably being overly pedantic but I think it's better stated that any electromagnet is an inductor but not all inductors are 'effective' as electromagnets. After all even a small DC current flowing in a length of wire produces enough magnetic field to move a compass placed close to it...
  3. CDRIVE

    Help with invention

    Oops, I did seem to miss Alec's post. Sorry Alec. Chris
  4. CDRIVE

    Help with invention

    Hop, I feel your pain but the prospect of shedding your shoes and uh.... underwear:eek: will help getting you through these tough times. Chris
  5. CDRIVE

    Help with invention

    Diane, welcome to Electronics Point. I figure I should do this lest you think that we're a gaggle of clucking hens. Please forgive us for digressing into personal banter. Be assured that it wouldn't have happened if we thought your question hadn't been adequately addressed. Since the entire...
  6. CDRIVE

    Water as a conductor?

    We'll set our sights a tad lower then. Go for getting in touch with things that you can see, feel, smell and touch. Like nature! ;) My favorite wildlife is the 'Double Breasted Bi-Pod Thong', found mostly along the shoreline. :) Chris
  7. CDRIVE

    Help with invention

    If you also need some retirement OJT I'm sure I can assist both of you simultaneously. It's the only science where class size won't deprive any singular student of the full curriculum. There is no such thing as missing a semester, chapter or topic. You simply make it up any damn time you feel...
  8. CDRIVE

    Water as a conductor?

    Hop, I'm sure you remember your posts where you pondered buying a live aboard boat. I know I told you that you should test the waters (so to speak) first. Never mind that... Buy the boat! PS: What southern drawl? Besides that,... absolutely everything reminds you of something! .... GET THE...
  9. CDRIVE

    ltspice

    Actually, components of the same part number don't have to be identical. I don't use LTSpice much but I do use Tina. With Tina I can easily change the value of just about any component parameter in its properties panel. Though this fact doesn't diminish the comments made regarding the pitfalls...
  10. CDRIVE

    Water as a conductor?

    Hop, that's just toooooooo cool! No electrolysis either! Will sedimentary deposits on the fiber optics affect it? Chris
  11. CDRIVE

    Help with invention

    Hop, since you're retired and moving to Florida we'll have to get together so I can teach you how to do it properly. You're not supposed to be "busy" doing anything. I consider myself a professional at it!:) Chris
  12. CDRIVE

    Sound activated alarm

    Colin, since our new member has the disability, not his Dog, that would be pertinent .... how??? o_O Actually, a better question would be why do you persist in incessantly posting stuff like this? :confused: Chris
  13. CDRIVE

    Simulating a Wheatstone Bridge/Extensometer

    Neil, if your looking for a virtually painless transition into microcontrollers check out http://www.picaxe.com/ Chris
  14. CDRIVE

    HELP: project not working

    What can I say? This is a priceless question! It's reminiscent of a Bombay help desk that asks "Did you plug the power cord into the wall outlet"? I think it deserves a drink. Never mind I don't need an excuse! :D Chris PS: I think Bombay has a new name but it's irrelevant because unless you...
  15. CDRIVE

    Water as a conductor?

    Fortunately most water is impure and do contain conductive minerals. The FET circuit that Duke eluded to will look something like this. I included R2 as a safety in the case that Water Level Probe 1 should ever make contact with circuit GND. The value of R1 isn't critical but the higher it is...
  16. CDRIVE

    Current Threshhold Detection circuit using ACPL-K370

    Craig, I must be loosing it because I skimmed through the datasheet but I didn't see a typical hookup for current monitoring, even though the datasheet states it can. I would expect to see a very low value resistor in series with the load to sense the E= IR drop across it. I'm not sure if this...
  17. CDRIVE

    Simulating a Wheatstone Bridge/Extensometer

    I'm glad your jumping in here because I thought the question revolved around the strain sensing mechanism / sensor not the output circuitry of the bridge. I'll be lurking and learning while y'all work it out. ;) Chris
  18. CDRIVE

    HELP: project not working

    Your spice app appears to be Proteus Isis. Put a current meter in series with the relay coil so you can monitor coil current. A voltmeter connected to pin35 will also aid in checking the logic state of that pin. Chris
  19. CDRIVE

    Simulating a Wheatstone Bridge/Extensometer

    Martin's post included the word "we" which is often a red flag. Since it appears that this isn't a class assignment after all and I've not worked with Extensometers, please feel free to assist. Martin, have you researched Piezo elements in conjunction with strain measurement? Chris
  20. CDRIVE

    HELP: project not working

    Please post the part number or the datasheet of your PIR. This way way can determine if it requires a pullup resistor as Steve pointed out. It will also help us determine whether its output is compatible with digital input pins of the uC. If not it would be best to input it to one of the the...
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