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  1. Audioguru

    Which is better for led

    How will you cool your high power LED?
  2. Audioguru

    Assistance in decoding a circuit diagram

    Yes, the two pins at the sides are common (connected together). The pin at the front is the other connection to this variable capacitor.
  3. Audioguru

    Assistance in decoding a circuit diagram

    That circuit is the simplest, worst quality FM radio that I have ever seen and it is missing most parts that are in a real FM radio. I think a radio kit will be the best for you to learn how to solder its parts to a circuit board that has a correct layout. It will have the correct parts and...
  4. Audioguru

    Help me in calculating base resistance for transistor

    If a transistor saturates well turned on) then its voltage between collector and emitter is 0.2V. Four 2.1V LEDs in series use 8.4V. With your 12V power supply then the 180 ohm LED series resistor has a voltage of 12V - 8.4V - 0.2V= 3.4V. Then ohm's Law calculates the current to be 3.4V/180...
  5. Audioguru

    AEC Chaser only lights first LED. Newbie needs help

    In the reviews for the chaser kit one person needed to add a supply bypass capacitor (which is mentioned on the datasheet of an LM555) to make it work properly and a few people said that their soldering probably fried the chips. Cheeeeep soldering irons that get too hot??
  6. Audioguru

    Question concerning increasing voltage for phone auxiliary speaker

    You do not need a separate battery to bias the LED. simply use a voltage divider to set the bias voltage then capacitor-couple the audio to the LED and its current-limiting series resistor.
  7. Audioguru

    Question concerning increasing voltage for phone auxiliary speaker

    The LEDs need DC but the amplifier output is AC. Without biasing the LED then it does not light until the signal AC peak voltage exceeds the forward voltage required to light the LED which might be 3V. Then the LED is turned off most of the time. I suggested to bias the LEDs through a series...
  8. Audioguru

    AEC Chaser only lights first LED. Newbie needs help

    When a 555 IC is used as an oscillator then the minimum resistor value for the resistor from pin 7 to the positive supply is 1k ohms. Your trimpot can be turned so that this resistance is zero which might destroy the 555 IC. The datasheet always shows a resistor from pin 7 to the combined pin 2...
  9. Audioguru

    Help me in calculating base resistance for transistor

    Most 5mm LEDs have their brightness and forward voltage rated at a current of only 20mA. Some of mine have a maximum allowed continuous current of 30mA. Four 2.2V LEDs in series use 8.8V then the current-limiting resistor will use the remaining 3.2V, then for 20mA the resistor will be 3.2V/20mA=...
  10. Audioguru

    AEC Chaser only lights first LED. Newbie needs help

    The instructions do not show a schematic but says to be sure that the polarity of C1 is correct. Maybe yours is backwards. The white line on the side of the electrolytic capacitor is its negative wire side. If you touched the battery backwards to the battery connector even only for a moment then...
  11. Audioguru

    Help me in calculating base resistance for transistor

    Again you do not say the color or voltage of the LED. If it is a white, blue or modern green LED then its voltage could be 3.5V and four in series need 14V plus at least 2V for the current-limiting resistor. They will not light up with a supply of only 12V. With a 12V supply the Texas...
  12. Audioguru

    Help me in calculating base resistance for transistor

    The datasheet for most little and medium-power transistors shows that for it to saturate well then its base current should be 1/10th the collector current. Then when the supply voltage is 12V the base resistor of 2.2k has 11.3V across it which calculates to be a 5.1mA base current for a 51mA...
  13. Audioguru

    Question concerning increasing voltage for phone auxiliary speaker

    So then the circuit board is not "the phone", instead it is the amplifier from an amplified speaker. Driving an LED from the output of an amplifier will result in no light from the LED most of the time then the LED brightly flashes for peak levels from the amplifier. I think it will look better...
  14. Audioguru

    Help me in calculating base resistance for transistor

    The 4017 is ordinary Cmos that has "rail-to-rail" output voltages when not loaded. The datasheet of a CD4017 and most other ordinary Cmos logic Ics lists a maximum output logic low voltage of 0.05V when it is not sinking any current. The base of an NPN transistor as a load does not source...
  15. Audioguru

    Question concerning increasing voltage for phone auxiliary speaker

    If your battery is a Lithium type and is at 4.7V then it is over-charged and is ready to catch on fire or explode. You need a lithium battery charger circuit that can be fed USB 5V. A Lithium battery charger output is never higher than 4.20V. You are biasing an LED with a DC voltage that is...
  16. Audioguru

    Help me in calculating base resistance for transistor

    Of course the +12V should have a supply bypass capacitor to GND with short leads. With the supply bypass capacitor added then the 4017 will work perfectly when the pin 3 output of the 555 directly clocks it without any added resistors.
  17. Audioguru

    Question concerning increasing voltage for phone auxiliary speaker

    You do not say the color or voltage required by the LEDs. You also do not say the voltage of the battery that you are using. If the LEDs do not have a current-limiting resistor or circuit then if you increase the battery voltage the LEDs will be too bright and burn out in a moment. I think if...
  18. Audioguru

    Need help resistor values

    There is no church with a steeple where I live but I frequently see bats flying at dusk in a nearby park. Maybe they live in a hollow tree trunk.
  19. Audioguru

    Need help resistor values

    JVH, your first thread did not explain clearly what you want to do. Your schematic shows a 555 timer, a pushbutton and a NC relay. You said you need the relay contacts to stay open for long periods. Then if the 555 timer was wired correctly as a timer like I showed, the Bat Repeller would be...
  20. Audioguru

    Need help resistor values

    You said that the relay contacts are NC which is Normally Closed. Then they conduct when the circuit and pushbutton are not used. You also said that you want the relay contacts to stay open for long periods. Then the pushbutton activates the 555 timer circuit which opens the relay contacts for a...
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