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  1. audioguru2

    Choice of op.amp. model

    Hi Gillyne, Welcome to our forum. ;D I have converted the filter circuit to a single supply voltage:
  2. audioguru2

    project help with toy IC boards

    The LM386 has fairly low distortion up to clipping. Maybe the 0.047uF capacitor will reduce yours. Maybe the distortion comes from the toy. It probably doesn't matter since the frequencies aren't high frequency radio waves where ceramic disc capacitors are needed.
  3. audioguru2

    motor driver L298 help

    Thanks, Ante. A tutorial about DC motor speed controllers by a major golf cart speed controller manufacturer says that when a free-wheeling diode is added across the motor to make it more efficient, then the frequency doesn't matter. The motor's inductance doesn't reduce the speed or torque, it...
  4. audioguru2

    motor driver L298 help

    No it doesn't! If you change the frequency of a square-wave that feeds a DC motor, the motor receives an average of half the supply voltage at every frequency until the frequency becomes so high that the inductance of the motor reduces its average current and slows it down. With a 50%...
  5. audioguru2

    Transformer Questions!!! ???

    Yes. If the wire in the transformer is thin and is a low resistance, and the 9V battery is new. The new battery can have an output current of nearly 1A for a few seconds into a low resistance. That much current will cause thin wire to burn like a fuse. Transformers are used with AC, not DC. Feed...
  6. audioguru2

    Resonator datasheet needed

    You have a wideband tuned circuit for shaping the IF of an FM radio. A microcontroller uses a narrowband resonator that is like a quartz crystal. Try the one you have, it might work.
  7. audioguru2

    Resonator datasheet needed

    You bought something and you don't know anything about it. Really? It has an input, an output and a ground. The input and output pins can be swapped, and the center pin is probably the ground pin.
  8. audioguru2

    Resonator datasheet needed

    It makes a big difference. There are ceramic resonators for AM radios, FM radios, shortwave radios and many other applications. There are many manufacturers, shapes and sizes. Digikey lists 563 different ones for sale. Which one?
  9. audioguru2

    RC-(remote controlled) Car

    The VHF amplifier and the power meter don't need their supply to be regulated. The output power will become reduced a little as the battery runs down.
  10. audioguru2

    RC-(remote controlled) Car

    An ordinary 12V regulator needs a minimum of about 14.5V on its input to work properly. Your 12V battery pack won't have enough voltage. Low dropout regulators are made for 5V and if somebody makes one for 12V then it would need a minimum input voltage of about 12.5V.
  11. audioguru2

    project help with toy IC boards

    The circuit in the toy is designed for only 3V. 9V will probably destroy it. If you can get it working properly with its own 3V battery like on your sketch I fixed, then I'll show you how to reduce the 9V down to 3V.
  12. audioguru2

    RC-(remote controlled) Car

    The 1nF capacitor you added reduces modulating frequencies above about 500Hz, and about 5kHz will be down -3dB. Your DTMF decoder might not work properly with the higher tones rolled-off. The varactor diodes look correct now.
  13. audioguru2

    High Voltage Stun Gun !

    AM portable radios have a ferrite bar antenna. The ferrite bar might make a good core for a high frequency transformer. Get one from a broken old AM radio. A transformer needs a proper core for its operating frequency. Low frequency mains power transformers use steel laminations for a core. Mid...
  14. audioguru2

    rechargeable battries

    A lead-acid battery will get its plates sulphated and not work anymore. It must never be completely discharged. A Lithium battery will also be destroyed. It must never be completely discharged. I have some that haven't been used or charged for about 8 years and they still measure 3.8V. A...
  15. audioguru2

    Data Transmission using Xmitters

    A radio transmitter can be AM or FM modulated. Data can be DTMF, ways using a phase-shift and many other ways. My local FM stations transmit data so my car radio shows the name of a song, the singer and all kinds of information.
  16. audioguru2

    amplify..

    There are lots of ways to draw a relay. Datasheets for relays have their schematic symbol. I copied this one from one of our projects:
  17. audioguru2

    skematic free nokia cell

    Thanks, Hack. I found the schematiscs for my cell phone. 10 pages of extreme detail and a microprocessor with about 1 million pins. ;D
  18. audioguru2

    High Voltage Stun Gun !

    If you don't use the correct parts then it won't work very well. It might not do anything except make smoke.
  19. audioguru2

    Audioguru FM Tx

    The frequency of the oscillator changes when the supply voltage changes. I used a low-dropout 5V regulator so my circuit's oscillator 's frequency doesn't change as its 9V battery runs down to about 5.5V. But then the output level of my oscillator is much less than AN920's oscillator. You can...
  20. audioguru2

    project help with toy IC boards

    Your volume control pot is intermittent and is brobably burned out from being connected wrong. It is probably needed for you to reduce the volume to avoid distortion. We don't know if the IC has a DC output which will mess-up the operation of the pot and the LM386, so the 0.22uF capacitor was...
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