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  1. Audioguru

    does someone know the function of R6,R8 and R9?Is it just current limiting

    When you learn about how a transistor works then you learn that the voltage gain is the ratio of the collector resistor in parallel with the load resistance, divided by the unbypassed emitter resistance. Your circuit does not have any unbypassed emitter resistor so the emitter resistance of the...
  2. Audioguru

    does someone know the function of R6,R8 and R9?Is it just current limiting

    The mic preamp transistor is biased wrongly so when speaking not even very loud it produces awful distortion:
  3. Audioguru

    Low cost electric skateboard?

    A motor without enough power will run slowly and will soon burn out. The weak motor can have a gearbox or pulley system (or even a chain and sprockets) to increase its torque by slowing down the skateboard. Don't you want a speed control? It is usually done with a Pulse-Width-Modulation circuit.
  4. Audioguru

    H-bridge over 6v dc engine

    The maximum allowed current for a BC337 is only 500mA. How much current does your "engine" use? For a collector current of 500mA then the base current must be 50mA then the voltage lost across the bottom transistors is 0.7V so they each heat with about 0.4W which is OK but near the maximum...
  5. Audioguru

    Need help to make telephone tap coupler schematic

    The telephone earphone speaker produces sounds from the caller PLUS sidetone of your own voice (so you can hear how loud you are speaking). If you don't want sidetone then you need a circuit like I showed to cancel it. Mic jack to connect your pc or mobile? The level of a mic is VERY low so a...
  6. Audioguru

    does someone know the function of R6,R8 and R9?Is it just current limiting

    They also goofed on the volume control that will do almost nothing when it is a rheostat like that. Its value should be about 20k ohms with a logarithmic audio taper and a capacitor on both sides of it since it will be grounded.
  7. Audioguru

    Linking circuits help

    A 555 timer normally does not have a capacitor to ground on pin 2. When it is powered then its pin 2 is high and it is not triggered so its output is low which lights the Red LED. When it is triggered then its output goes high during the timing which lights the Green LED then after the timeout...
  8. Audioguru

    Analysis the component role and FM frequency

    Bass sounds are missing because the value of C1 is much too small and cuts frequencies below about 1600Hz. Use 1μF for frequencies down to about 35Hz. The radio frequency is calculated with L1, C4, C5, the capacitance of TR2, some of the capacitance of TR3 and stray wiring capacitance.
  9. Audioguru

    First LED Cube

    The max allowed temperature is 125 degrees C for the chip inside the voltage regulator that you cannot measure! You are measuring its case that is much cooler.
  10. Audioguru

    LED SMD 10watt and Solar battery

    The LED needs a pretty big heatsink. A solar panel does not have a fixed voltage, The load reduces its voltage. My "12V" solar panel produces 18V with no load in bright sunshine and produces 12V at its rated current. Is your solar panel 18V when loaded or not? Does it produce 560mA at its rated...
  11. Audioguru

    Analysis the component role and FM frequency

    The circuit is similar to the one I fixed. TR1 is biased wrongly because it is saturated when the battery is new and/or the transistor has high hFE. TR1 is cutoff when the battery is low and/or the transistor has low hFE. The value of C1 is too low so it will cut all low audio frequencies and...
  12. Audioguru

    Linking circuits help

    Probably not without a circuit creating a trigger pulse. The 555 trigger must not be continuous or the timer will never time out. The trigger low must end before timeout or there will never be a timeout.
  13. Audioguru

    Need help to make telephone tap coupler schematic

    The phone has what is called "sidetone" for you to hear the loudness of your own voice. To cancel the sidetone you must mix the inverted and amplified mic signal to it. Here is an intercom circuit that uses a transistor to make the inverter and mixer but it does the opposite, it cancels your...
  14. Audioguru

    Linking circuits help

    We discussed on another thread that the light detector is not sensitive because the resistor values are much too low. The 555 timer begins timing when its pin 2 goes low that happens when the 0.1uF capacitor is discharged and power is applied. If the 0.1uF capacitor is removed and the timer is...
  15. Audioguru

    2 audio signals to a single fm transmitter

    Yes the stereo transmitter has two audio inputs, each one from a bite alarm. Why the radio system? All fishermen I have seen are very close to their poles and when a fish bites the pole wakes them up.
  16. Audioguru

    2 audio signals to a single fm transmitter

    Your transmitter is mono with a mono input? Then it has only one "hot" audio input that would short the left and right stereo channels together. If there is a signal on one channel and no signal on the other channel then there will probably be no signal to the transmitter. You need an audio...
  17. Audioguru

    CMOS 4001 Repeating Timer

    Get rid of the breadboard with messy wires all over the place and possibly intermittent contacts and build the circuit soldered neatly on stripboard (Veroboard) exactly as shown. You might have zapped the IC with static electricity from you touching it.
  18. Audioguru

    Lightsaber Mod!

    The "blob on board" might do the timing that cannot be changed. I have solar garden lights that slowly fade between red, green and blue then flash them and the blob does it all. I cannot change it.
  19. Audioguru

    2 audio signals to a single fm transmitter

    A 3.5" plug would be ENORMOUS! A modern headphones jack and plug are fairly small 3.5mm. A Y splitter would short the two outputs together which might damage them. The two added 1k resistors form an audio mixer.
  20. Audioguru

    Diode for thermostat circuit

    Diodes will combine or separate the relays only if the 24V that turns them on is DC and is not AC. A diode connects the thermostat to a relay and each relay needs a diode. A switch or another thermostat connects directly to the relay you want to turn on separately. 1N4002 diodes will work well.
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