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  1. audioguru2

    Aaaargh! 555 circuit works well with LEDs but not with relays...

    The max output current of an ordinary 555 (not a Cmos 555 which is less) is 200mA and with a 9V supply its output voltage is only 6.5V or 2.5V. So if the battery is brand-new then the relay coil gets much less voltage than the battery. When the relay is turned off it developes a very high...
  2. audioguru2

    Rechargeable battery - Rate of Self Discharge ?

    Energizer has a Ni-Cad Applications Manual on their website. It shows a graph of self-discharge that is much quicker than you have been told.
  3. audioguru2

    Electromagnetic field interference.

    The magnetic fields from the motors might cancel if they run in opposite directions, if the sensor coil is equally between them and if they have exactly the same current.
  4. audioguru2

    where can i get free samples from?

    Hi Spenymoor, Welcome to our forum. ;D I think you are gathering parts to make my 6V Ultrabright Chaser project. I ordered the inexpensive parts online from www.digikey.com and the plastic box was the most expensive part.
  5. audioguru2

    Plz help me in understanding this RF reciever

    It is a regenerative receiver that is connected so it nearly oscillates due to positive feedback through the 3.3pF capacitor. The transistor is a common-base oscillator, but with not quite enough positive feeddback to oscillate. Its gain at the tuned frequency is extremely high. It might also be...
  6. audioguru2

    Rechargeable battery - Rate of Self Discharge ?

    The self-discharge rate is higher with Ni-MH batteries as compared to Ni-Cad. The self-discharge rate is also higher with higher temperatures, so keep the battery away from sunshine.
  7. audioguru2

    multivibrator

  8. audioguru2

    How to use oscilloscope to analysis the audio signal

    An oscilloscope shows the waveform throughout a circuit and at the output of a circuit. Phase between channels can be shown by using one channel to deflect the beam vetically and the other channel to deflect the beam horizontally. Stereo music shows a constantly moving pattern, mono shows a...
  9. audioguru2

    Cold Heat Soldering Tool

    It is a wonderful piece of junk!
  10. audioguru2

    mosfets

    Why not look at a datasheet? Like for an IRF540 Mosfet: 1) The gate threshold voltage to cause the Mosfet to conduct only 250uA is between 2V to 4V. 2) It conducts best (33A) with a gate voltage of 10V. 3) Its max gate voltage is 20V. It is a Mosfet. Mosfets don't have gate current. BUT, its...
  11. audioguru2

    Simple question about measuring output of a wall mount transformer...

  12. audioguru2

    multivibrator

    Go to www.google.com and serch for Transistor Multivibrator. You will get links to more than 8000 articles about it. The reverse breakdown voltage of silicon transistor emitter-base junctions is only about 5V to 7V so don't use that very simple circuit with a supply voltage more than 5V.
  13. audioguru2

    Simple question about measuring output of a wall mount transformer...

  14. audioguru2

    Surround Sound for car audio

    In your Alt-a, the pot connects to GND (negative opamp supply) instead of to the half-the-supply reference voltage, so the bias for both opamps change with setting the pot. Also, R14 attenuates the signal to IC1B.
  15. audioguru2

    Surround Sound for car audio

    In your fix5 circuit, the DC voltage at the input (it could be 0V) determines the bias voltage of IC1B since there aren't input coupling capacitors. Also the input to IC1B is attenuated by the additional 100k resistor. In your fix5-alt circuit, pin 5 of the IC1B opamp isn't at half the supply...
  16. audioguru2

    Surround Sound for car audio

    You had some missing parts. You also had some extra parts including parts for positive feedback! I fixed the schematic.
  17. audioguru2

    How to use oscilloscope to analysis the audio signal

    The volume of music changes moment to moment so you can't measure or adjust it accurately. Just adjust it so it isn't too soft or isn't too loud. An oscilloscope is used to see clipping or other distortion on sine-waves that have a constant level. It can also show if the channels are in-phase...
  18. audioguru2

    How to wire two 555s in parallel?

    Two 555's cannot be paralleled, but Cmos inverters can. Here is a circuit to randomly flicker an LED's light. Change its capacitor values to slow it down and maybe it will be OK for your application.
  19. audioguru2

    Simple question about measuring output of a wall mount transformer...

    Cheap wall AC-DC adapters do not have voltage regulators. They deliver their rated output voltage only when they have their rated load current. An adapter with a higher output current rating has an output voltage that doesn't rise much without a load.
  20. audioguru2

    Surround Sound for car audio

    Noise is easy to eliminate. With a single supply, the half-the-supply-voltage reference needs filtering with a capacitor to ground as I showed. Then use shielded audio cables to connect everything together.
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