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  1. BobK

    Resonance

    You will have a lot more luck vibrating glass or plastic using sound. Bob
  2. BobK

    help for motor from laminator

    This thread got me started looking at laminators I would like to use a lamintor since it usually takes me several tries with an iron. This guy hacked the laminator by turning the motor on for 1/2 second and then off for 10 seconds to get the lower speed. Sounds like a good idea to me...
  3. BobK

    Driving LEDs from 12V

    I said to use 3 of them, one for each string of LEDs. Bob
  4. BobK

    Sleeping mask

    Okay, when I first followed you link, nothing played, and there was a "Click to Watch" button that played a the video I mentioned. Now the lucid dream mask video plays. Bob
  5. BobK

    Driving LEDs from 12V

    Yep. The currents in a parallel circuit add. 3 strings of LEDs drawing 350 mA is drawing 1005 mA altogether. Bob
  6. BobK

    SMPS feedback loop is "easy"?

    If the load is constant. Bob
  7. BobK

    DC adapter supply question

    Can you measure the voltage beteen the + and - (or ground) power leads from the powered device when using the adapater? Bob
  8. BobK

    DC adapter supply question

    You got me. If the adapter is the correct voltage and can supply the needed current, the circuit should at least mostly work. There could be problems with noise in the supply, but to act like there is no power is puzzling. Did you try measuring the voltage witht the adapter hooked up to the...
  9. BobK

    OP AMPS!!!!

    No, an op amp is a high gain differential amplifier. That is quite different than a resistor. Bob
  10. BobK

    SMPS feedback loop is "easy"?

    Not much of a feedback loop if the output is not included. Bob
  11. BobK

    Driving LEDs from 12V

    Not if you are using 3 strings at 350mA, that would be 1/3 what you have calculated. Bob
  12. BobK

    I need help building an amplifier for my mp3

    :) Well, I read your original post and, though not entirely clear, I was able to make a good guess at what you were doing. Bob
  13. BobK

    thanks for your help but its time I give up

    You may be trying to tackle too much too soon. Building your own electronics devices, and even better, designing them, are very rewarding, but you have to learn to walk before you run. Bob
  14. BobK

    Capacitors & Resistors in Amplifiers

    Filters are not necessarily to remove noise, they shape the response of an electronic circuit. For example, a specific response is needed to play back vinyl records. Resistors and capacitors are used for many purposes other than filters. Bob
  15. BobK

    Guitar static modulation morse transmitter--will my amp blow up?

    It does not work that way. In order to transmit, you have to produce RF. There is nothing in a guitar amp the produces RF. Bob
  16. BobK

    4017 Counter - Increments of 5. Electronics help needed. Simon Says using PIC?

    You can certainly program the micro to send a pulse only for every 5'th correct game. Bob
  17. BobK

    I need help building an amplifier for my mp3

    If you have stereo output from the MP3 player and want to run it into a mono amp, connect a 1K resistor from each MP3 output to the single amp input. Also, an LM386 has a minimal gain of 20db or 10X. This is too much for an MP3 output. You might have to hook another resistor (something like...
  18. BobK

    Driving LEDs from 12V

    As I stated before, with 12V you can only put a max of 3 in series. This string would use 350mA. For seven all together, you only choce is 3 regulators with 3, 2, and 2 LEDs. Each one would be regulated at 350mA. Or, if you could go to a higher voltage, say 28V, you could put all 7 is series...
  19. BobK

    Driving LEDs from 12V

    You said earlier that you got it working. So why are you asking this now? Also, why do you keep ignoring my advice that you want a current regulator and not a voltage regulator to drive LEDs? I do not understand your question. The LED would go between the ground and the Out+, but you...
  20. BobK

    Driving LEDs from 12V

    No, things in series all get the same current, in this case 350mA. You cannot put 4 in series and drive with 12V since they will take anywhere from 12 to 14.4volts and you will need about 2V extra for the LM317 to operate. You can buy constant current drivers that will driver all 7 of your...
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