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  1. Hero999

    LED Necklace

    Yes, a peak detector would help to improve the performance. Have you tried Googling for peak detector? A pot can be added to the input to adjust the sensitivity, try 100R.
  2. Hero999

    Energy conversion.

    Google for dynamic microphone.
  3. Hero999

    Power Plugs

    What sort of temperature does it have to withstand? Will one part of the connector be single use? It's difficult to know exactly what you want without actually seeing where it's going to be used. Have you check the usual suppliers, i.e. RS Components, Farnell, Digikey, Mouser etc?
  4. Hero999

    LED Necklace

    You should've asked that before, it should have been your first question. When there's no signal, the transistor will be off, no current will flow so the LEDs will be off. When the incoming signal is greater than the base threshold (typically 0.6V to 0.7V), the transistor will turn on and...
  5. Hero999

    Power Supply for capacitor bank

    It looks pretty straightforward and uses the same topology as the circuit from Wikipedia,  I posted above. The 555 acts as an oscillator which runs until the required voltage is reached and is shut-off by the comparator. The shut down occurs when pin 4 is taken to 0V, which happens when the...
  6. Hero999

    Power Supply for capacitor bank

    Look at the voltage across the MOSFET when it's in its off condition and it will give you an indication of the maximum voltage rating. For example in a typical boost converter the maximum voltage across the switch (MOSFET, BJT, etc.) is no more than the input voltage...
  7. Hero999

    LED Necklace

    Yes, that will work. The LEDs might be a bit dim with 150R, don't forget that they're only on for half of the time so will appear dimmer than they would if they were connected to a battery via the usual series resistor. Try it with 150R and reduce to 68R, if they're not bright enough.
  8. Hero999

    I need a simple leds voltmeter

    http://www.newcircuits.com/circuit.php?id=msr003
  9. Hero999

    LM338 Power Suply Current Regulator

    We will help you to solve your problem but we won't do it for you.
  10. Hero999

    computer engineering thesis proposals

    Please speak English and bear in mind that this is not a free coursework service.
  11. Hero999

    wireless electric billing... is it possible?

    I would havbe thought that they would use the phone line or possibly data over mains technology. A satellite link would require a dish which would be obvious.
  12. Hero999

    Automatic Fan Controller - Help (w/ relay?) Please!

    Yes, the time can be factored in, diodes can handle surges of higher currents for short periods, so it would be fine even if you used a diode with a maximum current rating of only 25mA, for example, the 1N4001 is rated to 1A but it can handle a surge of 30A for one 60Hz mains cycle...
  13. Hero999

    Automatic Fan Controller - Help (w/ relay?) Please!

    The type of diode really isn't important. Think about what the diode actually does, how much current it needs to carry and for how long and you'll see what I mean.
  14. Hero999

    Automatic Fan Controller - Help (w/ relay?) Please!

    You're on the right track, the only thing I would suggest is setting the centre point to in between the high and low temperatures, so that's a temperature of 27.5
  15. Hero999

    ghost detector circuit, 3 volts buzzer adition

    There's a lot wrong with your spelling, look at what you've just posted, there are at least three misspelt words: confuseing, countrys,  iether and probably more. Duh, audioguru deliberately misspelt the word English - any fool can see that. Seriously though, you would get more help if you...
  16. Hero999

    ghost detector circuit, 3 volts buzzer adition

    Why didn't you say so before? The more information you give, the better, From what you've said, it seems like it's working. There's probably a way to adjust the sensitivity and one of the resistors probably needs to be a pot. If you convert it into a readable schematic by drawing it with...
  17. Hero999

    Automatic Fan Controller - Help (w/ relay?) Please!

    The LM258 is an op-amp, not a comparator, there is a difference, read the article linked below for more inofrmation. http://people.na.infn.it/~barbarin/Biblioteca%20rivelatori%20ed%20elettronica%20%28per%20studenti%29/Elettronica/comparatori/sloa067.pdf No, it has a short circuit output current...
  18. Hero999

    LED Necklace

    What do you think? Compare the two schematics and check each connection one by one, you don't have to know anything about electronics to see that the connections on the one you've posted are wrong. I'm not going to go through it and list all the corrections when you're obviously not giving this...
  19. Hero999

    ghost detector circuit, 3 volts buzzer adition

    I'm glad it worked and hope your 3V buzzer won't be damaged when run at near 9V for long periods of time. Have you measured the votlage across the buzzer? It's possible the op-amp's internla resistance is lowering the voltage, it certainly won't be 9V, probably 8V at most bue could be lower.
  20. Hero999

    ghost detector circuit, 3 volts buzzer adition

    All right, I missed that. Why did you say 3V? That sounds about right for a red LED. The reason why it will work from a 9V supply but not from a 3V supply is that the op-amp has a typical saturation loss of 1V at 10mA, leaving only a fraction of a volt across the resistor so LED will be very...
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