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  1. audioguru2

    Digital logic circuit design

    Good, it works. A TTL Nand gate will light an LED brighter than an And gate, because TTL outputs have much more current going low than they have when they are going high.
  2. audioguru2

    Digital logic circuit design

    Without the resistor then pin 2 is high all the time. The resistor makes pin 2 a logic low voltage when the switch is opened, because the input of a TTL gate needs 1.6mA to ground to make it low.
  3. audioguru2

    Digital logic circuit design

    No. A resistor at the output to ground of a TTL gate is not required. It is guaranteed to sink 16mA to ground with a max voltage of only 0.4V when it is low. The output might not go high enough to light the LED if it had a resistor to ground.
  4. audioguru2

    Telaphone Receiver

  5. audioguru2

    Simple but sophisticated lab Power Supply

    You are looking for an expensive, bulky and dangerous capacitor that won't last very long to replace a very safe and reliable transformer.
  6. audioguru2

    Digital logic circuit design

    Hi Sundar, Welcome to our forum. ;D I was going to attach clips from the datasheet of a 7408 IC and of an LED, but I think you should find them and read them: 1) You are correct in thinking that when both inputs are high for an AND gate then its output is high, but your circuit doesn't make the...
  7. audioguru2

    Emulate a 10k thermistor

    Hi Virus, If anybody designed a circuit to emulate a thermistor, the circuit would be complicated and maybe way overdesigned since we don't know if it operates with AC or DC and we don't know how much voltage and current is required. It is nearly impossible to add parts to a circuit without...
  8. audioguru2

    Emulate a 10k thermistor

    An ordinary silicon diode, rectifier or transistor's junction is an NTC thermistor. Its forward voltage changes about 3mV for each degree C rise in temperature. It can be amplified and level-shifted to any value you want.
  9. audioguru2

    Turn ur VGA CARD tO TV

    If he wants to change a VGA card and monitor into a TV, then 1st he needs to understand about most of the parts in a TV.
  10. audioguru2

    amplify the power (infrared)

  11. audioguru2

    NiMH Battery Pack Charger

    The battery that you linked to doesn't have its physical size shown. So we can't know which standard size of Ni-MH cells are used. With a capacity of 1100mA/hrs, the cells could be old AA size because new ones are rated at 2500mA/hrs, or the cells could be AAA size with a very good mA/hr rating...
  12. audioguru2

    Electronic Stethoscope 2

    Hi Dazza, Your microphone case looks odd. I used a lid from a jar that made some air-space between the mic and the skin. I also used headphones that completely covered my ears so that the seal made very deep bass sounds.
  13. audioguru2

    Simple but sophisticated lab Power Supply

    It is not a sophisticated lab power supply circuit. 1) It has hardly any output current. 2) Its voltage regulation is not nearly as good as other voltage regulator ICs. An LM317 is sophisticated and is complex internally but its circuit is simple externally. It works much better.
  14. audioguru2

    Turn ur VGA CARD tO TV

    It is too bad that our project has the parts values wrong, a terrible translation and no pcb layout like the original that is written properly in English: http://www.tkk.fi/Misc/Electronics/circuits/vga2tv/circuit.html
  15. audioguru2

    datasheet

    An HA17555 is just an ordinary 555 that is made by most semiconductor manufacturers. It isn't even the Cmos kind.
  16. audioguru2

    Need help with a TV transmitter project.

    Build it and try it. It doesn't have anywhere near the number of parts as a real TV transmitter. I don't think its picture and sound will be clear. The IF transformer must have a frequency to match what TVs use in your part of the world. Some transformers have tuning capacitors built-in, others...
  17. audioguru2

    Electronic Stethoscope 2

    Hi Dazza, Welcome back. ;D Your project looks very well-made. How does it work?
  18. audioguru2

    Telaphone Receiver

    You won't learn anything if I do the work for you. If you just copy what I say like you copied the circuit then if your teacher sees it you will fail. Did you try adding a capacitor across R9 and did it increase the level of the mic? Did it cause acoustical feedback howling? Can you explain to...
  19. audioguru2

    Electronic Stethoscope 2

    The text in the project for the 2nd version has a complete circuit description:
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Same TO-220 package and pins layout, same voltage rating, same current gain, better current rating and better heat dissipation. It is perfect. A 5W resistor won't fit on the pcb. Use a 4.3k/1W or 4.7k/0.5W resistor instead and you won't notice that the LED is a little dimmer.
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