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  1. OBW0549

    It's 1890!

    Toilet paper and Fixodent.
  2. OBW0549

    Charged or discharged

    Thank you. I tried replicating the experiment you described in post #1 with my own USB booster battery. This is what I observed: First, I fully charged the battery and left it on the charger for a couple of hours with the light glowing blue. I then unplugged the battery from its charger and...
  3. OBW0549

    electromagnetism

    An electromagnet is simply an inductor with a mission: attracting ferrous objects. I imagine you could use an inductor as an electromagnet provided it can safely pass enough current to generate a strong enough magnetic field, and further provided it has an external magnetic field; some, like...
  4. OBW0549

    ltspice

    Very true, but the user needs to be aware that they will be identical unless he takes specific steps to make them different. 99% of the time this is not important; but it's the 1% of the time that bites you in the kiester. Yes, that's another VERY important point. Spice won't model parasitics...
  5. OBW0549

    Simulating a Wheatstone Bridge/Extensometer

    I like that idea, and it actually simplifies things a bit: EDIT: There's an error in note 5 on the schematic: 0x0400 should be 0x0800.
  6. OBW0549

    Audio amplifier to amplify a load cell signal

    An audio amplifier will not help with noise, it will just add complexity for the reasons I outlined above. The only way I know how to deal with noise/interference is through proper shielding and grounding.
  7. OBW0549

    Audio amplifier to amplify a load cell signal

    Not easily, unless you can arrange to excite the load cell with audio frequency AC drive. Normally DC is used to excite the load cell and it produces a DC output, which an audio amplifier would not be able to handle. Even then, you would have to somehow deal with the fact that most load cells...
  8. OBW0549

    Charged or discharged

    I think the electrons just get tired of going around in circles, and eventually sit down and refuse to participate any further. Then the light goes out.
  9. OBW0549

    ltspice

    Yup. Been there, done that. Another nasty little trick Spice is fond of pulling comes from the fact that in Spice, two or more transistors of the same type (2N3904, BC550 or whatever) are not merely similar to one another like they would be in real life, nor are they very similar to one...
  10. OBW0549

    Simulating a Wheatstone Bridge/Extensometer

    Thanks. I'm not sure whether this will help you or not, Martin, but the attached .pdf shows a schematic for a strain gauge simulator that I've used successfully in the past for testing precision strain gauge amplifiers for linearity, scale factor and offset voltage. I've modified it to...
  11. OBW0549

    Design Simple microcontroller circuit

    Definitely not! The 12F510 is an 8-pin device, and the 18F4520 is 40/44 pins.
  12. OBW0549

    Design Simple microcontroller circuit

    You say you switched from the 18F4520 to the 12F510, but the code you posted still uses the #include directive for the 18F4520. That might be the problem.
  13. OBW0549

    ltspice

    Thank you. Best of luck in your adventure, and enjoy the holiday!
  14. OBW0549

    ltspice

    Yes, I'd certainly recommend it; Spice can be a huge time-saver (it can also be a huge time-waster, but that's another matter) and it can be a valuable tool for gaining confidence that a design will probably do what you actually intended it to do, and for catching major design blunders. It is...
  15. OBW0549

    Simulating a Wheatstone Bridge/Extensometer

    I'm a bit new here, I'll admit; but I'm puzzled as to why you inferred that this was a class assignment. I would have guessed that the fellow is an engineer or a researcher, perhaps in a Materials testing lab. If this is indeed a class assignment, I won't post a solution; if it is not, I may...
  16. OBW0549

    Electronics Design Process

    I would propose doing with Steve's Step 5 something analogous to what I proposed for Step 3: identify those components with special performance requirements, and tackle them first. Some examples would be opamps with very low input offset voltage or offset voltage drift, passive components with...
  17. OBW0549

    Electronics Design Process

    There is a HUGE gap between steps 1 and 2, with a lot of important activity missing. The process (*steve*) posted fills in that gap. The only thing I would add to what he outlined would be a Step 3.1: Identify the most critical modules, i.e., those modules that have the biggest impact on...
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