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  1. audioguru2

    WHY A TRANSISTOR

    There are different kinds of field effect transistors: 1) Junction field effect transistors are low current and low power. They are N-channel or P-channel. Most are fully turned on when their gate voltage is the same as their source voltage (no bias voltage). They become turned off when the gate...
  2. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Omer, Other members have reported problems with the circuit that are not easily solved. It gives false indication of a transmitter nearby and it picks up all kinds of interference from computers and monitors, AM and FM stations, TV's, TV stations and taxi cab radios.
  3. audioguru2

    Sound Level Indicator

    When my rechargable battery is nearly dead all the LEDs light then turn off then light then turn off over and over. Maybe your battery is weak. All 10 LEDs use a high current and a weak battery cannot supply a high current. Without a signal, R7 holds the pin 5 of the opamp IC1b at 0V. Then the...
  4. audioguru2

    white led

    If the LEDs are in series and are the same make then they should all be the same brightness because in series the all have the same current. I guess your dim ones are not good.
  5. audioguru2

    synthesizer problems

    You forgot to attach your schematic so we don't know how the 4066 is connected and is powered.
  6. audioguru2

    WATER LEVEL MONITOR FOR PUMPS

    The circuit should work fine without the LEDs. The Cmos gates don't have enough output voltage when directly driving LEDs. So they don't have the proper logic voltage levels. Fix it by using inverters, gates or transistors as LED drivers.
  7. audioguru2

    WATER LEVEL MONITOR FOR PUMPS

    you made many modifications to the circuit. Post your new schematic and we will see what is wrong with it.
  8. audioguru2

    WATER LEVEL MONITOR FOR PUMPS

    I answered your questions about the Classic Cmos Oscillators in your other post.
  9. audioguru2

    help with the circuit diagram

    The Cmos gates and the resistor and capacitor between them form Classic Cmos oscillators. The first gate gates each oscillator on and off. EDIT: The "piezo buzzer" is not a beeper with a built-in oscillator. It is a piezo speaker.
  10. audioguru2

    Oxygen Sensor Tester (Design Idea)

    A neighbour has a new Volvo diesel powered car. It stinks and makes a noisy racket like an old Ford truck. Hey, it doesn't smoke.
  11. audioguru2

    SL100 & SK100 transistor

    I am an old geezer at 61 years young. I retired at 55 and I am having a great time bumming around. ;D
  12. audioguru2

    Oxygen Sensor Tester (Design Idea)

    No, I don't drive a stinky, noisy diesel. It was a '75 Volkswagen Rabbit. It was made for California with a deluxe catalytic converter that lasted only a couple of months. It frequently backfired which broke the catalytic and the mechanics did not know why. Sometimes it made black smoke and...
  13. audioguru2

    LED Tie Bar

    The ad doesn't say which battery cells are used. My LCD watch uses a 191 alkaline watch cell which is rated at only 52mAh at a current of only 100uA when the cell is new with 1.5V. It is tested with a 100 ohm load for 2 seconds. When the loaded voltage drops to only 1.05V (10.5ma) then it is...
  14. audioguru2

    SL100 & SK100 transistor

    I used the old germanium AC127 and AC128 transistors in 1967 when I worked for Philips. That was 40 years ago.
  15. audioguru2

    How to get better current from LM317?

    Hi Wellington, I don't see how the choke caused oscillation unless it has a high resistance. The LM317 can dissipate a little less than 2W without a heatsink. If it gets too hot then it shuts down until it cools, then starts working again. 2W from a 13.8V car battery to 3.0V is a current of only...
  16. audioguru2

    How to get better current from LM317?

    Hi Wellington, Your cassette motor uses a very high current to get started. The LM350 supplies 3A and the LM338 supplies 5A. There is a way to connect a PNP booster transistor to an LM317 but then you lose the current-limiter feature. A second transistor can be added for current-limiting. The...
  17. audioguru2

    white led

    I used Hewlett-Packard's LEDs for many years. Then their opto business was sold to Agilent who sold it to Avago. Digikey sell these excellent Avago LEDs at a pretty good price. There are forums for guys who eat and breath LEDs. They talk about the good and new brands of LEDs better than me.
  18. audioguru2

    white led

    Fairchild's MV8W00 white LED is narrow angle and is not as bright as modern LEDs. Digikey don't have any in stock so maybe it is not made anymore. Fairchild's website has old catalogs like the one you found. I don't think Fairchild makes LEDs anymore.
  19. audioguru2

    LED Tie Bar

    It looks a little smaller than the scrolling belt buckles that kids were wearing two years ago. The parts are probably hard to solder, tiny Surface Mount so I don't think there is a kit. The display is 7 dots high by 21 dots long. Only 7 dots light at the same time. If each red LED is 2V and...
  20. audioguru2

    LED Tie Bar

    A scrolling text display with LEDs uses a lot of current. Tiny watch cells are used for very low current LCD displays, not high current LED displays. You would need to use four AAA or AA cells.
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