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  1. audioguru2

    Car subwoofer and amplifier

    Thanks Ante, That's a very cool cap. But it costs more than a whole 500W amplifier! It would smooth the current flow from the alternator/battery and cancel the voltage drop on the 4-guage supply wire to the amp, allowing even more output power. Hey. That huge cap isn't big enough. It will supply...
  2. audioguru2

    LM317 Variable power supply

    MP, Certainly you can get 0.5A from an LM317 in a TO-220 package with an ambient temperature of 25 degrees C, without a heatsink. Just use a regulated input voltage that is 3.0V (no less) to 3.99V (no more) than its output voltage! Since it will be operating at its thermal limit, it probably...
  3. audioguru2

    Car subwoofer and amplifier

    Hi Ante, My son has started a pretty good business. He sees on a car chat thread that someone needs a part. Then he phones the local junkyard/car graveyard and they check their database. I have tagged along while we wander around there (it is huge without signs, you must count rows and columns)...
  4. audioguru2

    Car subwoofer and amplifier

    Hi Guys, My son just got a subwoofer and amplifier from E-Bay. We installed it with 4 paralleled 20A fuses! The amp is 350W RMS. I kept telling him to turn it down for proper balance but he likes it so that the bass kicks you really hard. My clothes were shaking with the beat! It is so loud that...
  5. audioguru2

    LM317 Variable power supply

    Hi Ante, For years I have been using the low-dropout LM2931 for all my 9V alkaline and 7.2V Ni-Cad battery low current projects. It sqeezes all the life out of the battery. The 7805 and LM317 get into trouble when the battery is stll new and their idle current is 10 times or more what my...
  6. audioguru2

    LM317 Variable power supply

    No heatsink? Oh yeah? Let's make a simple calculation without using extremes: 1) The LM317 is rated for 1.5A, but let's choose only 1A. 2) It is spec'd with a minimum of 3V across it, but let's choose a reasonable 5V. 3) Some parts of this planet reach 40 degrees C, but let's choose only 25...
  7. audioguru2

    LM317 Variable power supply

    Hi Ante, Why do we talk about making things cheap? We sound like baby chickens! We aren't mass producing these things. Let's make it good. There is a guy who is selling "the ultimate" audio amplifier for only $3,300US. Inside, it has only 2 National Semi's power amp ICs. You know how cheap...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ante, Thanks for the power factor article. I don't think that a reactive load that is supplied by our Lab Power Supply will feed back into it. Even the huge filter cap isn't reactive because all of its charged energy ( ;D) flows as current in the load, or if the load is very light then the...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ante, A transformer doesn't dissipate much because it isn't the load, unlike a linear power transistor that is in series with the load. A transformer passes VA to a load, therefore shouldn't be rated in Watts. Its rating in Watts is how hot it gets (power input minus power output). Since...
  10. audioguru2

    LM317 Variable power supply

    I agree Ante, But with the bypass transistor you lose short-circuit protection, unless you add an additional transistor, or let the LM317 get hot and shut-down itself and the bypass transistor.
  11. audioguru2

    Rechargerable Battery detector...

    Hi Ante, The old LM358 low-power dual opamp is cheap and available nearly everywhere. It is actually 1/2 of an LM324. It works well at these low supply voltages and has enough output current to drive an LED, unlike many rare CMOS opamps. Its total supply current is typically only 0.5mA, which is...
  12. audioguru2

    LM317 Variable power supply

    Hi Guys, some info: ;D The LM317 is guaranteed to have an output current of 1.5A with 15V or less across it. In order to protect itself from second breakdown, it cuts back on its output current with more than 15V across it. With a high input voltage and low output voltage, it is guaranteed to...
  13. audioguru2

    Rechargerable Battery detector...

    Hi again, Here's a simple circuit for you. The green LED will be on until the battery voltage drops to about 6.1V, then it will turn off and the red LED will turn on from 6.1V down to about 4.2V. Decrease the value of R1 or increase the value of R2 to raise the voltage's trip point. Use only...
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ante, His 75VA transformer is already overloaded since its peak voltage of about 34V must supply the project's rated DC output current of 3A, which is 102VA. At the transformer's limit, this project can supply a DC output current of only 2.2A. I figure that with a very light load or none...
  15. audioguru2

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

    Hi Kain, Do you also know of a power transformer manufacturer who gives away samples? ;D ;D Q1 does not need a heatsink. It conducts only for a few seconds when you turn-off this project, to pull its output voltage immediately to 0V.
  16. audioguru2

    Rechargerable Battery detector...

    Hi again, 1) Is this battery voltage indicator circuit used in the battery charger so that the low voltage green LED lights to show that it is charging normally, then the red LED lights to show that the battery is fully charged? 3) Please post the schematic of your battery charger. Since the 14...
  17. audioguru2

    Rechargerable Battery detector...

    Hi, Welcome to our forum. A "9V" rechargeable battery is actually 7.2V to 7.5V, or 8.4V to 8.75V, during most of its discharge time, depending on how many NI-CAD or NI-MH cells that it has inside. A disposeable 9V battery has six carbon-zinc or alkaline 1.5V cells inside. It is called exhausted...
  18. audioguru2

    Power MOSFETs

    Kevin, Look at the datasheet for any power Mosfet and you'll see that its gate capacitance is thousands of picoFarads. Such a high capacitance requires a high current gate driver to charge and discharge the capacitance quickly, so that the Mosfet doesn't heat too much during its switching...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Emiliano, Please don't get fried. The OPA445AP is the only very high supply voltage rated opamp that I could find that is still being manufactured. It is made by Texas Instruments (previously by Burr-Brown). What country are you in? Look for your flag at www.farnell.com and you might be...
  20. audioguru2

    Question about ttl IC

    Hi Suraj, IC manufacturers also make mistakes, even on their datasheets. Look at the protection diode that is recommended by Panasonic in figure 2 on page 10 of their 79Lxx negative voltage regulator datasheet: http://rocky.digikey.com/WebLib/Panasonic/Web%20data/AN79Lxx,AN79LxxM%20Series.pdf It...
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