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  1. Hero999

    Audio amplification question

    In the modified circuit, the gain can be varied between 1 and 11 not 10. You're not haveing a good day are you audioguru? ;D Incidentally, there would be nothing wrong with being able to set the gain below 1 on an inverting amplifier.
  2. Hero999

    fax machine

    Posting the make and model number might get you some helpful replies. I doubt it though.
  3. Hero999

    Audio amplification question

    Correction: the inverting amplifier wil have an adjustable gain between 0 and 10.
  4. Hero999

    need help for electromagnet projects...

    What level? Primary School? High School? Special School?
  5. Hero999

    display old threads

    Unfortunately that's not possible. All posts before 24th January 2009 have been lost due to an error in the database. http://www.electronics-lab.com/forum/index.php?action=profile;u=34329;sa=showPosts;start=392 Previously all posts were replaced with symbols but they've notw changed to an...
  6. Hero999

    Most liked components

    This is a silly question as fars as I'm concerned. I don't have a favourite component, I just use what gets the job done in a particular application. If I want a stable low current 5V power supply I'll use a regulator such as the LM7805, if I want to siwtch a motor on and off I'll use a power...
  7. Hero999

    Power supply ignorance

    It's probably a SMPS so this is pretty normal. The power supply has a maximum power rating, this means that at higher voltages the maximum current will be lower than at lower voltages. The maximum power rating should be listed somewhere in the specification. Having a maximum power rating...
  8. Hero999

    Re: Wave Bubble?

    For the third and final time a jammer will only make it worse.
  9. Hero999

    Extending PWM potentiometer wires - how far?

    It depends on the PWM circuit. The resistance shouldn't be a problem since the potentiometer's resistance will dominate but inductance and capacitance (if the potentiometer forms part of the oscillator) or noise pick-up could be a problem. Do you have the schematic? Noise can be reduced by...
  10. Hero999

    need help!pls..

    What are you trying to do? Naughty, naughty you shouldn't be spying on the girl's changing room. ::)
  11. Hero999

    Speaker Magnet

    Why not? If another magnet in phase with the speaker magnet makes the field stronger then another magnet out of phase the speaker magnet will make it weaker. Surely a stronger field means higher sensitivity and a weaker field means lower sensitivity.
  12. Hero999

    Using a toroid in a xtal radio

    I don't see why not.
  13. Hero999

    Re: Wave Bubble?

    That sounds a bit complicated for something they stick on your car.
  14. Hero999

    Is this a typo?

    Yes, it should be R2.
  15. Hero999

    Speaker Magnet

    Doesn't that lower the sensitivity?
  16. Hero999

    Re: Wave Bubble?

    I doubt they're continuously bribing the police, many  wealthy people have been arrested, put on trial and sentenced. The idea that they've somehow corrupted the local authorities doesn't make sense, of course bribery and corruption do occur but there's a difference between bribing the odd...
  17. Hero999

    A/C switching through PC

    A typical opto-TRIAC can only take a couple of hundred mA which isn't enough for an air conditioner. It's up to you, you could use a transistor and relay if you like. All I'm saying is that it's wasteful to use both an opto-isolator and a relay.
  18. Hero999

    Re: Wave Bubble?

    Have you done anything to upset someone with a lot of money? Be honest, you haven't sold anyone poor quality drugs have you? If you've ripped off a gang then be prepared to pay.
  19. Hero999

    A/C switching through PC

    That will work, assuming the opto-isolator is rated to carry the relay current. It seems a bit overkill to use both an opto-isolator and a relay. I would have used either an opto-TRIAC triggering a TRIAC or a transistor and relay. Relays are more fail safe than TRIACs but have the...
  20. Hero999

    Engine Speed Controller

    Aren't engines limited anyway? Unfortunately they're normally set at the start or the red line but you might be able to adjust it to a more sane maximum speed. Alternatively you could use an optical tachometer. Are you using  a microcontroller? If so it should be easy to count the pulses...
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