Search results

  1. audioguru2

    geophone kit circuit reqest

  2. audioguru2

    geophone kit circuit reqest

    Hi Steven, Here is the way your 741 inverting opamp should have been connected:
  3. audioguru2

    Telaphone Receiver

  4. audioguru2

    Telaphone Receiver

    It disables the mic preamp so you can't be heard when you want some privacy. It is a little Philips amp (1W with a 6V supply) in the parts list but an LM386 would also work fine and give about 1/4W with a 6V supply.
  5. audioguru2

    Please help me in this problem

    The TDA7000 is an obsolete FM radio IC that operates very poorly. Unlike other FM radios with a 10.7MHz IF, it uses a 70kHz IF and uses muting to cover up the resulting very poor image rejection. It increases the effective bandwidth and linearity of its IF by modulating it with the detected...
  6. audioguru2

    Telaphone Receiver

    Your circuit will have feedback when its mic preamp has enough gain. A hybrid transformer or two-opamps bridge circuit can offer a little amount of separation between the transmitted sound signal and the received sound signal. In addition, speakerphones use press-to-talk switching, "voice...
  7. audioguru2

    geophone kit circuit reqest

    It doesn't work with its inputs at the negative supply voltage, and it has many other problems. So the 741 works like a piece of wire. The LM386 amp has a gain of 200, which is plenty. Try the coil connected like this:
  8. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Kain, It looks great! ;D
  9. audioguru2

    Telaphone Receiver

    Design Equations won't do any good until you find out the specifications of a telephone: 1) The max current of the ringer so you can select an AC ringer with the proper impedance. 2) The allowed transmit level on the phone line and sensitivity of your microphone. Then you can calculate the gain...
  10. audioguru2

    Telaphone Receiver

    The schematic on the text page is missing many wires. Download it and you will see that C2 is a big supply filter cap. It is the telephone line's current modulator for the mic signal. The zener diode with the big C2 across it is the voltage regulator.
  11. audioguru2

    Why electronics-lab takes longer time to appear

    I have also noticed that this site loads slow lately.
  12. audioguru2

    Telaphone Receiver

    The ringer in a phone in North America operates on 90VAC/20Hz and with a very low current. Your phone has a DC buzzer that might need a very high current. Your mic preamp doesn't have enough gain. Try adding a 4.7uF capacitor across R9 for much more gain. Then the value of C9 will need to be...
  13. audioguru2

    Plants Watering Watcher-2 by Audiguru

    Actually, the actual input voltage of a Schmitt trigger input does not determine whether the output is high or low. The direction of the input voltage (positive-going or negative-going) plus the actual voltage determines it.
  14. audioguru2

    Plants Watering Watcher-2 by Audiguru

    Sorry, Walid. I am doing my income tax and my son's. Also, it is springtime and I have gardening to do. Correct for this ordinary Cmos Schmitt trigger gate, but 74HCxx gates are a little different. Yes.
  15. audioguru2

    Audio meter with 1 watt Luxeons

    Hi CK, I planned using a center-tapped 12V transformer to make 7.8VDC. It doesn't need to be regulated. A 5V supply voltage is too low. There will be hardly any voltage across very low-value current-limiting resistors to allow for differences in the LEDs' voltage and resistor tolerance.
  16. audioguru2

    Convert 0-30V 3A PSU to 5A or more

  17. audioguru2

    Converting negative analog voltage to positive

    Opamps are inexpensive, small and work very well. A single transistor has a 0.65V offset voltage that would need adjustment to reduce, and it changes with temperature change. You could use a two-transistor differential amplifier as an inverter. It is the input stage of an opamp.
  18. audioguru2

    Converting negative analog voltage to positive

    An inverting opamp with the input resistor the same value as the negative feedback resistor, and positive and negative supplies.
  19. audioguru2

    4 Watt Fm

  20. audioguru2

    Need help with a TV transmitter project.

    I think the circuit is too simple for a good picture. A real TV transmitter uses a complex wideband video amp and RF tuning that is wide and flat for one sideband. The sound in this project spec's a 4.5MHz transformer used in United States TVs. Other parts of the world use a 5.5MHz transformer.
View older results
Top