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  1. audioguru2

    I am having problems with an antenna...

    The receiver operates at a very high radio frequency. You cannot use a breadboard at high RF frequencies. The datasheet says that a perf board (which is much better than your breadboard) "will result in horrible performance and is strongly discouraged". What are those things that are at each...
  2. audioguru2

    A very Urgent Question

    Hi Walid, You forgot to attach the schematic of the "person detector" that drives the LED. I think it uses a light sensor and a comparator. The comparator must have hysteresis for it to be a snap action very fast switch. Datasheets for comparators show that hysteresis is a small amount of...
  3. audioguru2

    Transformer question

    Kevin, You want a transformer primary winding to have a high reactance, when the secondary doesn't have a load. Then the transformer doesn't draw much current when it shouldn't. When you add a load to the secondary then you want the magnetic coupling to transfer power from the primary to the...
  4. audioguru2

    summing ampliier can i connect to GND intead Vcc-

    Are you talking about an opamp circuit? Any opamp will work with a single polarity supply voltage if its inputs are biased to about half the supply voltage. Connect the negative supply pin to ground and make a voltage divider to make the bias voltage. But most opamps cannot swing thier output...
  5. audioguru2

    High Power LED Mood Lamp

    Hi Ante, The base current of the BC517 darlington transistor must be limited by a resistor. The PIC has high-speed powerful Cmos transistors like the 74HCxx series, so when the PIC output goes high but it is held to only 1.4V then its current will be typically 55mA.
  6. audioguru2

    Free wheel rectifier

    Kevin, Hold both coil terminals of a relay in one hand. Apply DC to the coil. Disconnect the power to the relay's coil and you will get a strong shock from the resulting hundreds of volts as the collapsing magnetic field cuts through the windings and generates the high voltage. The resistance...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    This original project does not get hot in Italy? 1) The transformer is rated for 24VAC/3A which is only 72VA. The peak voltage is 34V and if the project delivers 3ADC then the transformer supplies 102VA and is 142% overloaded. Sure it gets hot. 2) The 2N3055 transistor can dissipate about 70W if...
  8. audioguru2

    power supply cutting out

    Instead of connecting an amp-meter in series with the motor, which reduces the voltage to the motor and doesn't show the very quick peak starting current, just measure the DC resistance of the motor with an accurate ohm-meter that can measure very low resistances. Then use Ohm's Law to calculate...
  9. audioguru2

    Radio Noise

    Try connecting to the motor two 0.1uF ceramic disc capacitors with very short leads. Each capacitor from each terminal to the motor's metal case. It would be difficult to filter the radio signals. If all the interference is filtered out then the radio won't pick up stations.
  10. audioguru2

    power supply cutting out

    Those power supplies have a max output current of only 25A each for a moment. When connected in parallel then the one with the slightly higher voltage supplies 25A and the other one does nothing. It might be possible to set them to exactly the same voltage then use resistors to make them share...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    You can connect two 2n3055 transistors together or three MJE3055 transistors together like this:
  12. audioguru2

    High Power LED Mood Lamp

    Hi ante, The BC517 darlington transistor has a typical base-emitter voltage of 1.4V at the current used by the LED. When a PIC output goes high then a base resistor is needed to limit the current to less than 25mA. The max current in this project is much lower than the 350mA rated current of...
  13. audioguru2

    500W sine wave inverter design

    Why does a tiny car have an engine? The car is propelled with pedals, isn't it?
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    An MJE3055 is in a little TO-220 plastic case that is too small to dissipate all the heat from this powerful project. Many more parts need to be upgraded. 1N4001 and 1N4007 diodes have a max current allowed of only 1A which is too low. The 1N5402 diodes in the original parts list are rated for...
  15. audioguru2

    Drop amps from 25A to 8A

    The power supply doesn't provide 25A all the time. It provides only as much as the load needs. If you reduce its output current with a resistor then a load will receive a reduced voltage. 13.8V at 8A is a load resistor of 1.725 ohms. Its power dissipation is 13.8V x 8A= 110.4W. If you connect...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    The 2N3773 is a little bit better than a 2N3055 but it is not twice as good so two still must be used in the improved project. With a 30VAC transformer, the unregulated positive supply voltage is 40.4VDC. If the output is set to a low voltage or if it is shorted then the output transistor must...
  17. audioguru2

    Need help with LED display circuit

    Hi K, The 7805 needs a heatsink for cooling. Its input voltage is very high and causes it to heat nearly 3 times as much as if it has an 8V input. The inductor L2 destroys any high frequency voltage regulation for the ICs and should be removed. Then C3 and C4 will provide a low impedance supply...
  18. audioguru2

    guitar fuzz effect

    A loudspeaker must be driven from a power amplifier. This fuzz effect circuit can be the input to the power amplifier. The fuzz effect circuit has an opamp that has a very low power output.
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Aqmas, Welcome to our forum. ;D Are you going to make the original project? It has problems. Its transformer is too small and gets too hot. Its Q2 and Q4 transistors get too hot. Its rectifier diodes get too hot. Some resistors get too hot. Its opamps operate with a supply voltage higher than...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    You mean a 1W resistor. Sure, but unless you also change a few other resistors then the max output current will try to be 32A. Also, U3 opamp will need to have its input offset voltage adjusted to zero.
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