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  1. Hero999

    Please help me?! I want to graduate engineering project communication simple ...

    Sorry we only help via the forum not email. What do you need help with?
  2. Hero999

    Basic Controllers

    It means an input with CMOS logic levels. This is because modern microcontrollers use CMOS technology. Wikipedia has lots of information: http://en.wikipedia.org/wiki/CMOS http://en.wikipedia.org/wiki/Logic_family#The_CMOS.E2.80.93TTL_logic_level_problem http://en.wikipedia.org/wiki/Logic_level
  3. Hero999

    Need the Circuit for SMPS

    Then find one which closest meets your needs and adapt it. That's not a full specification. How much are you willing to pay for someone to design it for you?
  4. Hero999

    Need the Circuit for SMPS

    You may get more help if you provide a proper specification. You also need to learn how to use Google...
  5. Hero999

    circuit isolation

    You could build your own dual 5V isolated PSU using a transformer with twin 9V secondaries and have a bridge rectifier, filtering capacitors and LM7805 on each secondary.
  6. Hero999

    lm7805 question

    All that means is that if the capacitor is too small, it won't be large enough to damp the oscillations but if it's a single, large value capacitor it won't be good either. Higher value capacitors tend to have poor high frequency characteristics and become inductive past the resonant frequency...
  7. Hero999

    Sine Wave to TTL converter

    Yes, a Schmitt trigger will certainly work. If you use a comparator IC such as the LM311 or LM393 you can fine tune the hysteresis band to get the best results.
  8. Hero999

    lm7805 question

    You could have answered that yourself if you had bothered to read the first two links I posted previously.
  9. Hero999

    Powering a device with Ac and Dc

    You may get more help if you provided more information, such as what the device actually is? You could put ORing diodes after the regulator and if you're cleaver you can configure it so it only looses a diode drop when running off the battery. Oh and the LM7812 needs between 2V to 3V to...
  10. Hero999

    lm7805 question

    The value isn't critical. I'd also recommend adding a 100nF ceramic capacitor to the output as it has better high frequency characteristics. The addition of capacitors is known as bypassing or decoupling and it touched on in the LM7805 data sheet. http://www.ti.com/lit/ds/symlink/lm340-n.pdf A...
  11. Hero999

    Function Generator Simulation (Need Help)

    If you expect good marks then you should build it properly. I recommend calling this the first prototype then building it again more neatly. It's not just a fire risk but a shock hazard too. The cables are so poorly soldered a live mains wire could easily break off and touch the case causing it...
  12. Hero999

    Function Generator Simulation (Need Help)

    Why bother making your own power supply if you do it badly? You can probably get a crappy cheap Chinese power supply off ebay for much less than it cost for all of the parts and it'll be much more reliable too. You'll be lucky if it doesn't catch fire or electrocute you.
  13. Hero999

    INTERFACING DEVICES

    We can't help you if you don't provide any information.
  14. Hero999

    2n2222 resistor value

    Assuming Vcc is the same as the voltage powering the MCU, as a general turle of thumb, make the base resistor 10 times the value of the relay's coil resistance.
  15. Hero999

    Recelled Laptop battery now it won't charge Help Please...

    A safety feature of battery management systems is to refuse to charge the battery again once the voltage has dropped below a certain level. The only way round it is to reset the battery management system.
  16. Hero999

    Double Stage AC to AC Switch Mode Regulator(220V A.C.

    How much are you willing to pay for someone to design it for you?
  17. Hero999

    Lithium-ion batteires

    Oh so basically you're looking at building a battery powered 5V PSU with USB sockets? If would work of course but why use lithium ion cells? If go for 4 NiMH C sized cells which have a similar energy density but are safer and have the added advantage of being able to be charged by a standard...
  18. Hero999

    Flyback Help

    It sounds like the secondary voltage on the flyback exceeded its maximum rating causing the insulation to fail, arc over and internally short circuit. The only fix is a new flyback. To prevent this from happening again do the following: add more turns to the primary or reduce the power supply...
  19. Hero999

    Multi led scanner circuit

    What's an LED scanner? Don't you mean a sequencer of chaser? Two CD4017s and some transistors could be used to do this.
  20. Hero999

    step motror

    What do you mean by a classic motor and why do you want to do this? Stepper motors have poor torque and lower speed compared to DC motors.
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