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  1. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Here is a schematic of the transistor oscillator inside a Panasonic piezo beeper:
  2. audioguru2

    simple ac dc field detector circuit

    Good, but it connects to pin 7 on your schematic. Your battery will last longer without having those shorted-together outputs fighting with each other. All companies make the 4017. Motorola's has their part number of MC14017. I think they mark their numbers with a laser beam, so I hold it on an...
  3. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, My piezo speaker from an alarm clock is without a housing and its back is exposed. It is much louder when its back is very close but with a small space around it to a big bottle cap like from Coke. A sewing thimble also works well as an acousical resonant chamber. My piezo buzzer is...
  4. audioguru2

    simple ac dc field detector circuit

    The two diodes don't do anything and should be replaced by a wire.
  5. audioguru2

    i need help extending the keys finder project. can someone help me out????

    My piezo buzzer reliably works with a supply voltage of less than 1.24V. it isn't loud with such a low voltage but it works. Return your bad one and take your own 1.5V battery cell with you to find a good replacement.
  6. audioguru2

    simple ac dc field detector circuit

    Hi Steven, The IC is Cmos with inputs that can be destroyed by static electricity when they aren't terminated. Therefore I have added a 1M resistor in series with the antenna to reduce damage from static. Your circuit had outputs pin 7 (output pin 6 on your breadboard) and pin 10 connected...
  7. audioguru2

    Negative Voltage Rail Sag

    It provides current for the shunt voltage reference. The 56k resistor was calculated from refering to the datasheet of the voltage reference. Perfect. However a 3.3V zener diode is a lousy voltage reference. Its voltage changes with its input current and load current. Its voltage changes with...
  8. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, Now you have time to build this project and to modify it so it works. You enquired about a tutorial about opamps. This long document from Texas Instruments is the best one that I've seen: [attachment deleted by admin]
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    It is too small. It would need a very high speed fan to dissipate 120W.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Vaclav, 3 transistors are even better than 2 because they share the heat and have a higher current gain so their driver transistor will be cooler. The heatsink must still be big enough to dissipate up to 120W. Don't use insulators then they can conduct their heat to the heatsink better...
  11. audioguru2

    Help with making aux. 5V battery pack

    Hi Sean, Welcome to our forum. DON'T put a 5V zener diode across your 6V battery. It current will be infinite and blow the zener and kill the battery very quickly. Connect a 1N4001 diode in series with one of the battery's wires, the right way around, and its output voltage with new battery...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    I also get many e-mails and PMs about this project. "I built this project and it blew-up . Please help me". I refer them to this thread.
  13. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, Besides having a broken beeper, your project doesn't work because of your intermittent breadboard. As we discussed on MSN, the Whistle Responder project's design has some mistakes that can be easily fixed: 1) It uses an unsymmetrical output, high operating current CD4049. That's...
  14. audioguru2

    Negative Voltage Rail Sag

    Hi Mr. Freckles. hee, hee. ;D I checked and double checked and think they made a mistake. The 910k resistor's value must be much higher for a -5V output and much higher again for -9V out. The 100k resistor connected to it could have its value reduced instead. Calculate the resistors using Ohm's...
  15. audioguru2

    i need help extending the keys finder project. can someone help me out????

    The lousy old intermittent breadboard stopped the circuit from working.
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Gogo, You can make this project any way you want. Make the kit and when you complain about its poor performance and unreliability then maybe the maker will replace it with one that works. I've fixed and built many projects on this site and get thanks from many people and an argument from...
  17. audioguru2

    help me in finding this output from a single op-AMP

    Hi Shaiq, You said that you are going to connect the voltage divider to the output of an opamp? Don't you mean its input? Then check the input bias current for the opamp that will load down or pull-up the 5V from the divider. Don't you think that the extremely low output impedance and 20mA of...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi One Eye, You don't need this complicated project. You need only a 14VAC to 15VAC 3A transformer, a 5A rectifier bridge module and a 10,000uF 25V filter capacitor. Its output will be 18VDC at 2A.
  19. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Like this:
  20. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Logan, You are using a different IC. Which pin number does what????? Please post a schematic with the pin numbers you used so I can see what they do and which ones if any have a wrong voltage, or a cross-reference list. Your meter wavers because the oscillator is running at about 8Hz.
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