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  1. Hero999

    ghost detector circuit, 3 volts buzzer adition

    The circuit would be easier to understand if proper op-amp symbols were used rather than just a box. I don't know how it works and am not going to redraw it with the proper op-amp symbols so I can figure it out. I assume you could connect a small piezo buzzer across the LED and its limiting...
  2. Hero999

    LED Necklace

    No, it's still wrong. Look at the circuit I posted at the start of the thread, change the component values to those suggested by me and reduce the battery voltage to 6V.
  3. Hero999

    how to program a microcontreller ?

    What sort of microcontroller?
  4. Hero999

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

    It sounds like the transistor has failed, it shouldn't do that. The LM258 is not a comparator and doesn't have enough output current capacity to drive a relay directly, you need the LM311.
  5. Hero999

    Signal distortion for common power supply

    It sounds like the resistance and possibly the inductance of the power supply leads is too high. The question is does it really matter? If it's driving a MOSFET or an inductor in an SMPS and there's a 100mV glitch on a 10V waveform it shouldn't matter. Anyway you haven't provided enough...
  6. Hero999

    LED Necklace

    No because you've now connected the LEDs in series so the minimum operating votlage is doubled.
  7. Hero999

    DC conversion for AC welder using a Bridge Rectifier & Capacitor or Inductor

    TO be honest I've never actually done this before so I wouldn't be able to tell you exactly how many turns wound over what core, I'm remembering a suggestion made my someone on another forum I no longer post at. All I can say is, get a thick bar of ferrous metal and wrap as many turns of thick...
  8. Hero999

    DC conversion for AC welder using a Bridge Rectifier & Capacitor or Inductor

    Inductors are better at smoothing higher currents. Capacitors are better at smoothing lower currents, especially at higher voltages. You'll need a huge capacitor to smooth 225A to say 5V ripple, think somewhere in the region of 0.5F.
  9. Hero999

    LED Necklace

    The transistors are now connected backwards. Yes, the 2N3904 or 2N4401 will do, it really isn't critical. The voltage is too low for two LEDs connected in series, 0.5V isn't enough headroom and if you'd read my previous post, you would have realised that the batteries won't last very long. I...
  10. Hero999

    PWM help please

    The MOSFET will always be in the active mode, unless something else such as the cell or wiring resistance limits the current because when the MOSFET is on there is nothing to limit the current. The circuit will not behave like an SMPS because it's missing the all important energy storage...
  11. Hero999

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

    You've got it connected upp as per my schematic with the LED in series with the base resistor? You could try adding 1k between the base and emitter. Here's an example using the LM311 comparator. http://www.silicontronics.com/index.php?action=ezportal;sa=page;p=17
  12. Hero999

    DC conversion for AC welder using a Bridge Rectifier & Capacitor or Inductor

    Use an inductor rather than a capacitor, try wrapping ten or so turns round a large iron bar and be careful not to get stuck to it if you're wearing steal toe capped shoes.
  13. Hero999

    What will I use?

    That site doesn't give any information about the camera. Have you asked the seller? That's probably the best place to start.
  14. Hero999

    LED Necklace

    The circuit will not work because the LEDs are connected backwards. I don't know if the transistors are connected correctly because you haven't used the correct symbol for them. Don't worry about the peak detector, although it will improve the circuit's performance, it's not essential. It's...
  15. Hero999

    PWM help please

    What's it supposed to do? Zero Fossil Fuel? Sounds suspecious, is it supposed to improve the fuel economy of a car? If so, it certainly won't work, if it were that simple car manufacturers would include it as part of the car. Anyway, linear mode is a bit of a confusing term when it comes to...
  16. Hero999

    What will I use?

    That's right. You need four times the amount of power to transmit over twice the distance or use a more directional aerial and sacrifice the ability of being able to receive from all directions. You need to provide more information, if you've no idea of what frequency they operate on you've got...
  17. Hero999

    [ARTICLE] Build your own UV exposure box

    The partn umber and photo indicates they emit UVA which is non-hazardous unless you do something stupid like stare at it from close range or hold the tube next to your skin for ages whilst it's on.
  18. Hero999

    direct current stimulation

    You're right of course but this means nothing if when the 'what if?' brigade get involved in order for a device like that to get medical approval. The general rule is that no single point failure shall endanger the person using it. Now as far as both you and I know, transistors are reliable and...
  19. Hero999

    direct current stimulation

    I think you'll need to have more than 60V to ensure that 1.5mA flows,the resistance of dry skin can be very high and even with a saline solution you might not be able to go below 60k. The trouble is no more than 60V should be used for safety reasons as there's a chance the transistors will fail...
  20. Hero999

    direct current stimulation

    Yes, that should do the job.
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