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  1. Audioguru

    Looking for advice for an LED flag project

    Hee, hee. Post a video of your LED flag on fire. I made a night light with 36 powerful LEDs a guy sent to me. Boy oh boy did it get HOT! Of course the LEDs were running at about 75% of their maximum allowed current (VERY bright at night) and the case had many holes for cooling but there were too...
  2. Audioguru

    Looking for advice for an LED flag project

    The spec's for the Cree LEDs you selected do not say their minimum voltage. If you design for 20mA with "3.2V" LEDs and do not have enough voltage for the resistor then if the LEDs are actually only 2.8V then they will soon burn out. If the LEDs are actually 3.8V then they will not light. You...
  3. Audioguru

    Relay not energized

    Of course the ebay module does not have detailed spec's. Instead of saying if its sensitivity is "100 Lux" its says "adjustable".
  4. Audioguru

    Looking for advice for an LED flag project

    LEDs are not light bulbs with a filament. They are a semiconductor and have a range of forward voltage. For example the "3.1V" blue LEDs might have some with 2.8V and others with 3.5V. Or they all might be 2.8V or 3.5V. Then you must reduce how many LEDs are in series and increase the resistors...
  5. Audioguru

    Relay not energized

    The datasheet for the relay says that the coil is 47 ohms so its current will be about 4.8V/47 ohms= 102mA of current but the maximum current allowed for a BC547 transistor is 100mA as shown on its datasheet and for a collector current of 100mA its base current should be 10mA for all BC547...
  6. Audioguru

    Relay not energized

    He said it is an LDR. Some LDRs are sensitive and some are not because they are cheap. I measured a 'typical" LDR in fairly dim light about the same as a clear sky at sunrise or sunset, and at the light where most of my solar garden lights turn on or turn off. The resistance is 6k ohms. Then...
  7. Audioguru

    Relay not energized

    We need to know the current used by the relay coil, the part number of the transistor and how much light there is. The relay coil is an inductor that produces thousands of volts when it is turned off that will zap the transistor if a protection diode is not added.
  8. Audioguru

    Milliamp power supply question

    Some electronic circuits use almost no current sometimes then use a lot of current when they are working hard, like an audio amplifier. Then you want a power supply that does not allow its voltage to fluctuate much, but it does not need to be regulated with a voltage regulator IC, instead it...
  9. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    It is a strange circuit.
  10. Audioguru

    Joining NiCd batteries - conducting glue

    I remember that I needed to zap my Ni-Cad cells with a charged capacitor. The cells developed a short circuit from crystalline formation inside them.
  11. Audioguru

    Joining NiCd batteries - conducting glue

    Ni-Cad cells were used a long time ago. They are not used for much anymore because they are toxic and have problems. Why not use modern Ni-MH cells instead? My AA Ni-Cads had a capacity of 600mAh. My modern Ni-MH cells are 2300mAh which is almost 4 times more. New Ni-cads held a charge for 2...
  12. Audioguru

    Need help and ideas

    The Philips speaker is only 4W so the current from the battery is only about 4W/6V= 667mA at full blast, or an average of about 133mA when playing speech or music. It does not come with a battery. Ni-Cad battery cells are very old and had low capacity, maybe yours are finished. Modern...
  13. Audioguru

    I need to power a synthesizer with a battery...Please Help :)

    The battery has enough power to create a fire if something is shorted so you must add a suitable fuse or circuit breaker in series with it.
  14. Audioguru

    sharp deck with protect fault

    Did you short the output of an audio amplifier? Did the amplifier detect the short then disconnect it but allow the amplifier to work properly when the short was removed? Or did the amplifier detect the short and remain in the "protect' mode when the short was removed? Then the STK IC is...
  15. Audioguru

    Can you help me test a transistor

    The datasheet from Motorola shows the schematic of its insides and its pins. It has one silicon junction between its base and its collector with a forward voltage of about 0.65V. It has two silicon junctions in series between its base and emitter with a total forward voltage of about 1.3V that...
  16. Audioguru

    Circuit help?

    No. A Ni-MH cell is charged to 1.4V to 1.55V. Then the resistor values must be re-calculated..
  17. Audioguru

    Newbie Project

    Use a car alarm powered from a 12VDC wall-wart.
  18. Audioguru

    Powered Speaker Amp repair

    There is no 300V. R121 does not come off the transformer. The rectifiers are not a bridge, they are simple half-wave. The TDA7294 IC has short circuit and thermal protections.
  19. Audioguru

    Bogen multicom 2000

    If the school bell has a solenoid and contacts that spark then the sparks cause interference that affects the Bogen intercom. Use a modern electronic bell instead of an old mechanical bell.
  20. Audioguru

    Sound Bar

    In the Menu of my TVs there is a selection for its sound to have adjustable volume from the TV remote or fixed volume then the sound system remote controls it. I have the TV remote control its volume in the sound system.
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