Recent content by Jonathan

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  1. J

    Sold/Expired Feeler: CREE R2 WG/WH XR-E LEDs $11 shipped anywhere

    How much are you selling the Q5s for? Are they bare emitters, or mounted on stars? -Jon
  2. J

    Thor Boost Signup feeler thread

    My apologies for posting in the wrong thread. I should have known better but screwed up. Technical discussion moving back where it belongs! -Jon
  3. J

    Thor Boost Signup feeler thread

    Jarhead, I recognize that there are always engineering trade-offs, cost being one of them. I am proposing an alternative approach for you to consider, but expect that it is also not the 'best' approach. This is why I suggest an alternative approach, not a 'better' approach. For different...
  4. J

    Thor Boost Signup feeler thread

    Hi, I don't want to throw water on an ambitious mod, but I'd like to suggest a different approach. A switching boost converter produces a regulated output voltage that is greater than its input voltage. It does this by repeatedly storing energy in an inductor and then dumping it to a...
  5. J

    Question - PWM effieciency??

    If your measure of efficiency is 'electrical power delivered to the LED/electrical power supplied by the battery', then IMHO the PWM system will be more efficient. The power losses in the MCU and the FET are almost negligible as compared to your load. But if you measure efficiency in terms of...
  6. J

    Question - PWM effieciency??

    [ QUOTE ] I don't understand how do you PWM at 100% [/ QUOTE ] Think of 100% and 0% as the limiting cases of your modulation. At 0% or 100%, your output is no longer pulsing, but presumably your modulation system is _capable_ of pulsing the output and is still running some sort of internal...
  7. J

    Question - PWM effieciency??

    markus_i, I believe that you are spot on with one small nit: the rough estimate of power supplied to the lamp will be the _RMS voltage_ times the _RMS current_. Another way to figure things is to find the _peak_ current, multiply by the _supply_ voltage, and then multiply by the duty...
  8. J

    LED Warning!

    Just to inject a little balance to the calls for 'just use common sense', LEDs can present dangers that incandescent lights do not. The common sense point of 'don't stare into bright light sources' is spot on, with one problem: just what is bright, and how do you know when something is too...
  9. J

    Led Accelerator and Peter Lowrie

    Led-FX, Thanks for the links, I followed them, and I think that Peter actually has a nugget of an original idea. He has also 'spilled the beans' on the basic concept of the idea, and by 'offering to sell' without having done the patenting work, he has greatly reduced the value of the patent...
  10. J

    *Update* *Pics* Building a 12-cell NiCd/NiMH pack

    Re: Building a 12-cell NiCd/NiMH pack Hmm. I think that the only potential problem is the part about 'assuming the two packs share the current evenly.' When you put two loads in parallel, say two resistors, the current _never_ balances exactly evenly. But if the two loads are reasonably...
  11. J

    Ebay sniper tool?

    'Sniping' is a double edged sword, and essentially converts an open auction into a closed bid auction. You can still lose to someone who bids higher than you, and you also run the risk of paying more than you should in order to 'win' an item. Say you want an item, and it is worth $100 to you...
  12. J

    regulated incandescent light?

    Consider these little beasties. http://www.cs.indiana.edu/~willie/lvr.html
  13. J

    why do so many people hate the united states.

    People _hate_ for many reasons. But trying to figure out why someone _hates_ you has little chance of actually solving any sort of problem. As ikendu noted above 'People don't plan for years, spend tons of money and get an entire group of men to separately and deliberately commit suicide...
  14. J

    Fuel Cells in Laptops by 2004!

    Sorry to jump in on this late, but it looks like there has been lots of discussion and far more light than heat than one would expect when discussions get heated. Good job. Just for the record (Darell and I have discussed this before, and I just want to add a _slight_ counterpoint for...
  15. J

    Which soldering iron, folks? ***UPDATE: METCAL!***

    Re: Which soldering iron, folks? Look for 'Kester UltraPure Tip Cleaner'. This is a little tin container with a paste of tin and fluxing materials. Cleans the tip _beautifully_ and then tins it. Great thermal conductivity. I also _really_ like the Weller WES-50. This is either the top of...
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