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  1. audioguru2

    PSU WITH LCD VOLTMETER--TROUBLE!!

    The DMM IC that drives an LCD display and is the sister to the DMM IC that is used in our LED display project works from an isolated supply or a positive and negative supply. The inverter takes the positive 5V and makes a negative 5V. Then the IC can measure its own supply voltages.
  2. audioguru2

    Constant current source for high brightness LEDs

    The base-emitter voltage of the little transistor is 0.72V. When the 2.2 ohm resistor has 2.2V across it then its current is 327mA. 5V supply minus 2V for the LED and minus 0.72V for the base-emitter voltage of the little transistor = 2.28V. 320mA of current x 2.28V= 730mW. 5.25V supply minus...
  3. audioguru2

    Harman

    Hi Mukhalled, Did you see their history? Good old stuff: The 1st hi-fi receiver. The 1st FM tuner. The 1st FM multiplex stereo tuner. The 1st stereo cassette recorder/player. The 1st Dolby-B stereo cassette recorder/player. Huge, high power and high quality amplifiers. Etc.
  4. audioguru2

    PSU WITH LCD VOLTMETER--TROUBLE!!

    You say that your meter circuit works fine when it is powered by a 9V battery. Our DMM project has an IC that makes its -5V from +5V. Maybe yours will work the same:
  5. audioguru2

    Harman

    Look in Google. Harmon Kardon used to be one of the top 3 American hi-fi components manufacturers in the '60's and '70's. Now Harmon International is based in France and owns them, Crown, Infinity, JBL, Mark Levinson and many more well-known brands. ;D
  6. audioguru2

    plz help

    4 ohm speakers are used in cars. Home speakers are 8 ohms. An ordinary car radio provides 3.8W or 14W to a 4 ohm speaker. Compare the weight of your speakers to speakers with power ratings in stores. A more powerful speaker has a larger magnet and weighs more. Except some expensive speakers use...
  7. audioguru2

    25v transformer to run 2 '200w' amps.

    You have had very bad luck. :'( I have made many powerful amplifiers that work fine.
  8. audioguru2

    my radio is changing stations by itself!

    Supplying current to what? The varactors are turned-off transistors that don't conduct current. I don't see any large value filter capacitors that would take a long time to charge. You have 62k plus the DAC so a total of about 100k ohms charging the 1nF coupling capacitor from the varactors. So...
  9. audioguru2

    Low-pass Filter?

    Change the transformer's voltage. Change all the transistors to higher voltage ones but use less. Add a voltage regulator for the oscillator and add gain to the opamps. It is like a complete re-design. You are a mechanical engineer? Then how can I cut the weight of my car to half so it can go...
  10. audioguru2

    Constant current source for high brightness LEDs

  11. audioguru2

    need help for cfl lighting

    I have lots of newer compact fluorescent bulbs in my home. The tube is a spiral. Most use 15W and a few use 23W. The electronic ballast which is part of my bulbs pre-heats the filaments at the ends of the tube for a moment then gives it a high voltage spike to start it without flickering. The...
  12. audioguru2

    Why doesn't my inductor give more kick.

    If your 'scope survived, what did it show? No. What wire size and core for the inductor? What impedance, voltage, pulse width and fall time was the input pulse to the gate of the Mosfet?
  13. audioguru2

    Need help identifying part

    Is it called "a Polyfuse"?
  14. audioguru2

    Why doesn't my inductor give more kick.

    To make a high voltage spike from this single coil and Mosfet, you need a high magnetic field in the core, good coupling of the coil to the core and a high di/dt (fast rate of change). He might not have a high magnetic field in the core due to core saturation, not enough current or not enough...
  15. audioguru2

    Why doesn't my inductor give more kick.

    Hi Indulis, I was talking about a step-up power supply that uses a single Mosfet and only a coil, not a transformer. The circuit is about the same as H_Man's circuit and they don't step-up the voltage very high. Cell phones use them to light a string of LEDs. Silicon Chip magazine has a couple...
  16. audioguru2

    Constant current source for high brightness LEDs

    This is a very simple constant current sink circuit so it is far from perfect. Its load current will rise a little when the supply voltage increases, mainly because the current in the upper resistor increases, therefore the current in the lower transistor will increase, causing its base-emitter...
  17. audioguru2

    Why doesn't my inductor give more kick.

    What? Mosfets have a fairly high drain to gate capacitance that is amplified by The Miller Effect. If the gate's source impedance is high then the negative feedback caused by The Miller Effect is strong. The body diode of a Mosfet has reverse-biased avalanche breakdown like a zener diode. That...
  18. audioguru2

    Why doesn't my inductor give more kick.

    That is how a switched-mode stepup power supply works, but it doesn't stepup the voltage very high. For a higher stepup, a transformer is used with this coil as its primary winding, then the secondary winding has many more turns. An auto-transformer with a single, tapped coil can also be used...
  19. audioguru2

    Constant current source for high brightness LEDs

    The 2N3904 transistor has a base-emitter voltage of 0.72V when it conducts 7mA, as shown on its datasheet. It takes a current of 327mA to make a voltage drop of 0.72V across the 2.2 ohm resistor. If the current in the 2.2 ohm resistor tries to increase then the 2N3904 gets a higher base voltage...
  20. audioguru2

    Photosensing circuit problem

    The load resistance for the photo-diode must be a higher value than for a photo-transistor because a photo-transistor amplifies the photo-current and the photo-diode doesn't amplify. Here is how it should be wired:
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