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  1. BobK

    SMPS Build...

    What is the point of using a switching regulator, then increasing the current with a pass transitor? This just turns your switching regulator into a linear regulator with all the disadvantages of both. Bob
  2. BobK

    World's Smallest Torch

    I love it. Ferrite Joule Thief rings. This could be a killer product! Can you get ferrite in fashion colors? Of course, this could turn some jewel thieves into Joule Thief thieves. Bob
  3. BobK

    Resonance

    I don't get it. Back in post 7, I asked what you were trying to do. Here was your reply: What does an FM receiver have to do with this? Or have you just changed your mind about what you want to build? Bob
  4. BobK

    Emitter Base Breakdown

    Great stuff. So now we know how to get a lower Hfe transistor if we need one :) Bob
  5. BobK

    cellphone battery charger

    Or get this type of battery and charger. http://www.ebay.com/itm/2pcs-Blue-UltraFire-3-7V-2400mAh-18650-Li-ion-rechargeable-Battery-Charger-/190704681225?pt=Battery_Chargers&hash=item2c66e28109 Bob
  6. BobK

    Magnet passing through a copper pipe

    Where is the opposing force coming from when the magnet stops moving? Bob
  7. BobK

    Oscillating SPDT Relay Help

    30 - common 87a - NC 87 - NO 85,86 coil It looks to me like your circuit should buzz. Bob
  8. BobK

    Can one coil be a generator?

    Have you ever seen one of those flashlights that you shake to power? Bob
  9. BobK

    Digital electronics

    Transistor logic is always going to have an inverter. You would need to add an extra inverter to get an AND or OR gate, so you might as well make the NAND and NOR the primary gates and derive the AND and OR from them + an inverter. Bob
  10. BobK

    Laser fence?

    Did you bother to do a google search? This was the 4'th hit on "laser fence" http://www.tequipment.net/RamseyElectronicsLTS1.html Bob
  11. BobK

    how to detect laser reflection with photodiodes

    I don't think you could accomplish that with simple photodectectors. A video cam with a microprocessor scanning the image to look for the dot would be a possibility. Bob
  12. BobK

    Help in Timer circuit

    So change either the resitor or capacitor. Pick one and you can calculate the other. T = 1.1 * R * C Pick 470uF, then solve for R. T is 15 * 60 = 900 s 900 = 1.1 * R * 470 / 1000000 900 / (1.1 * 470 / 100000) = R = 1.74MOhms That said, the leakage is going to be high enough that...
  13. BobK

    Generators

    Yes, or the first post in answer to question might as well. Bob
  14. BobK

    driving 7 segment LED

    Link ot the display you found. Large LED displays often have multiple LEDs per segment and require a higher voltage. Bob
  15. BobK

    cellphone battery charger

    Don't do that, the battery could explode! A charger must control the voltage / current delivered to the battery and know when to stop. Charge your cell phone battery inside the cell phone, where the correct circuitry is there to charge it. Bob
  16. BobK

    how to detect laser reflection with photodiodes

    I am not sure I understand what you are talking about. Where are the photoreceptors? Are you talking about making a device that can follow the dot, pointing itself at the target? Bob
  17. BobK

    Resonance

    So you really are not talking about 500Mz? Bob
  18. BobK

    Resonance

    And there is still the problem that if you are amplifying this to more and about 100mW and putting it on an antenna, you are breaking the law. Bob
  19. BobK

    How to trigger a triac?

    Or use an optically isolated triac. Bob
  20. BobK

    Emitter Base Breakdown

    I guess it depends on the amout of current! Bob
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