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  1. Hero999

    Calc current leads

    The resistance of the copper wire can be calculated using the formulae in the Wikipedia article linked below: http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity The power dissipation can then be calculated using Ohm's law.
  2. Hero999

    I want to become PCB Designer

    Do you have any qualifications? You say you have 5 years experience using Altium but is this working on your own hobby projects or professionally? If you don't have any qualifications and have only done it as a hobby, your best bet is to look for a job as an apprentice and get the proper...
  3. Hero999

    i need help for designing a circuit gives 20 mA output using battery source

    What are ytou trying to do? Quite often a resistor will do. A simple constant current source can be built using an LM317 but it has a high drop-out voltage, typically 2.75V at 20mA.
  4. Hero999

    What are these?

    The look like capacitors.
  5. Hero999

    Power Supply Question

    Rather than messing around with PDFs, the address to the original image is at the top of each page. It doesn't look like it'll work very well. The peak value of VCC will be around 15*sqrt(2) - 0.7 = 20.5V.  Q1 and Q2 are source followers with a voltage drop of over 5V for even a small current...
  6. Hero999

    Energy Plug Meter

    I got an energy meter free from the energy company but the batteries ran out and now it's hardly used.
  7. Hero999

    question about circuit breaker

    A thermal circuit breaker would do.
  8. Hero999

    Yamaha Yzf R125 Speedometer Led Mod

    Let's get this straight: you're replacing red LEDs with blue ones right? If so, it's no surprise it'll be dimmer: the human eye is less sensitive to blue light (although this is somewhat negated by the fact blue LEDs are very bright) and the higher voltage drop means less current will flow...
  9. Hero999

    power supply

    That's not the correct way to design it. You need to calculate the current first, before you can build a power supply. If you build a power supply which doesn't provide enough current, the voltage will fall below 5V and the circuit won't work. If you over engineer the power supply so it can...
  10. Hero999

    Decrease cutouts PCB

    I don't use that software. Could you please post a PNG,  GIF or PDF so I can see it.
  11. Hero999

    power supply

    Are you sure it's 100Vpp and not RMS? 100Vpp is the same as 35VAC RMS. Most transformers are specified in RMS and it's unlikely you'll be able to find one with a 35V primary as it isn't a standard mains voltage in any country.
  12. Hero999

    555 HV FB

    The feedback is normally talken via an opto-coupler to give isolation between the primary and secondary side.
  13. Hero999

    1-25 volt power supply

    There's nothing special about an op-amp. It's just a differential amplifier with a very high gain. In the circuit posted above, all the op-amp does is try to keep the voltage on the inverting and non-inverting inputs equal by adjusting its output voltage. The voltage across R2 will be nearly...
  14. Hero999

    high pass rc circuit .

    The AC component of the signal remains the same. The high pass filter blocks the DC component and there appears to be some DC bias on the output which isn't shown, otherwise it would be centred around 0V.
  15. Hero999

    buffer circuit before rlc

    The buffer has a high input impedance and low output impedance and is used to avoid the effects of loading.
  16. Hero999

    remote controled door 10 second delay

    I agree with the above: you should test the 555 timer circuit first to be sure it works on its own. If the relay is already being driven from a transistor, there's no need for a diode. Have you connected the 0V rails of both circuits together? There needs to be a common 0V reference for the...
  17. Hero999

    remote controled door 10 second delay

    Did you use a back-EMF protection diode? How much current does the relay take? You may need to add a transistor to drive the relay.
  18. Hero999

    1-25 volt power supply

    Your circuit uses more components and is inferior. It doesn't have to have a gain of 1. It's possible to use a higher gain. See the circuit attached which has a gain of 10, enabling a more accurate 2.5V reference to be used, rather than a zener diode. It also has current limiting and a...
  19. Hero999

    remote controled door 10 second delay

    Most capacitors in this value range have poor tolerance/stability. Ceramics are probably the worst as far as stability is concerned. The capacitance drops as the bias voltage increases and they're often piezo electric, i.e. when they vibrate, they generate electricity. Electrolytic capacitors...
  20. Hero999

    remote controled door 10 second delay

    That's true but there's no point in trying to aim for any decent level of accuracy, when typical capacitors have a tolerance of 20%.
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