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  1. audioguru2

    How to transmit music from PC to music system wirelessly...??

    The BH1417 first came out in about 2001 or 2002 to replace the BA1404 that worked very poorly. There are still many kits available that have the old BA1404. Buy an MP3 to car radio transmitter. I have seen them in stores and they are not expensive. The good ones use a BH1417 IC and have the DIP...
  2. audioguru2

    Christmas Pin

    A red LED needs about 2V no matter what is its size. A blue or white LED needs about 3.5V. A small one makes less light than a normal size one and a low current would make it even dimmer. Look at my Ultra-Bright Chaser projects. My circuit blinks each LED for a very short amount of time to save...
  3. audioguru2

    What RF trancievers will work...?

    A crystal makes a very stable frequency that is accurate and doesn't drift. The IC multiplies it so the output is an accurate and stable 2.4GHz. The inductors tune the receiver to to 2.4GHz with a capacitor or two, and are transmitting filters so double and triple 2.4GHz harmonics are reduced...
  4. audioguru2

    Doubling 7805 regulator current is effective?

    Hi Wellington, Here we can buy anything with any value. I can order anything online before 8:00PM and it is delivered the next morning. You have 15.5W of heat to get rid of. One transistor will make a heatsink the same temperature as two transistors. The only advantage for using two heatsinks...
  5. audioguru2

    Christmas Pin

    Most watch batteries are only 1.5V when brand new. Most red LEDs are 2V and other colours need more. I checked the spec's of a pretty big lithium coin cell with a good power rating. It is spec'd for a load current of only 0.19mA for a watch. It might not power an LED for very long.  The...
  6. audioguru2

    What RF trancievers will work...?

    Hi CPW, I didn't read all 43 pages of the datasheet so I don't know what most pins are for. Decoupling capacitors filter a voltage so it doesn't change quickly. At 2.4GHz just a short piece of wire is an inductor that can resonate and be a high impedance on a line that must be a low impedance...
  7. audioguru2

    4ch rc schematic help

    Hi Sengo, The cheap RC micro cars use 27MHz and 49MHz so two can be used at the same time. The "servos" are just a small coil of wire around a small magnet and are just on and off. These tiny planes must be lightweight or they fly like a brick (won't fly). A guy on the web is selling a micro...
  8. audioguru2

    Doubling 7805 regulator current is effective?

    Hi Wellington, Two transistors with the same part number have a different current gain and a different bese to emitter voltage. So if they are in parallel then the one with the highest gain will have the lowest base-emitter voltage and will hog all the current then overheat and fail. Then the...
  9. audioguru2

    4ch rc schematic help

    The most important part of that very old article is missing, its modulation. Its old radio ICs might not be available anymore. I went to a meeting of a model airplane club. They had tiny planes that were controlled by the motor, electronics and controllers from a $10.00 micro RC car. The planes...
  10. audioguru2

    What RF trancievers will work...?

    Hi CPW, I don't see a "ground" pin on the chip. It has four VSS pins. If you don't know what the bunch of capacitors are for and don't know what is a 16MHz crystal, then mayb you should buy the assembled module. Is this the schematic that you are talking about?
  11. audioguru2

    Audioguru FM Tx

    Hi Walid, The jFET in an electret mic should have a higher voltage gain when its load/powering resistor value is higher, not when it is lower. At first glance I thought they are talking backwards. Then I thought about the tiny amount of current the jFET in the mic is conducting and how small is...
  12. audioguru2

    What RF trancievers will work...?

    The wire for an antenna should not be too thin. If it can hold itself up in a wind then it is OK.
  13. audioguru2

    How I can make a headphone amplifier

    Hi Cabwood, I don't have an electric geetar but all their preamps on the web have a 1M input impedance. This one is only 9.1k which is nearly a dead short to a high impedance pickup. I think that is why it doesn't work. Maybe the resistors across the supplies are to hold down the unloaded...
  14. audioguru2

    Is there a big difference between an FM transmitter and an FM receiver?

    My new car was made with its deluxe radio and many speakers. Its extra cost didn't hurt too much. It works perfectly and sounds great.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Hana, R1 is across the unregulated positive supply. Its power dissipation is easy to calculate: 1) If you have the original 24VAC transformer then it will be about 26VAC without a load on the project. Its peak voltage is 36.8V and is reduced to 35.4V by the rectifier bridge. So the power...
  16. audioguru2

    5 second delay System

    Hi Clue, Thanks for the full explanation. No mice. It is difficult to make a high quality recorder/playback device. You can buy a cheap IC that is made for toys that makes a very distorted and narrowband noise but I think you need something much better. There is a pretty good delay device that...
  17. audioguru2

    What RF trancievers will work...?

    The cable feednig the antenna should be coax with the recommended impedance and the length of the antenna should match the frequency.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Hana, If you have your 18VAC plus 18VAC transformer wired for 36VAC then the very high DC voltages will damage many parts. The original project spec'd a tiny 1/4W resistor for R2. Many members complained about it overheating so I recommended using 2W.
  19. audioguru2

    How I can make a headphone amplifier

    Hi Cabwood, The original preamp schematic shows a positive supply and a negative supply. So I think its output is at 0V plus or minus the amplified input offset voltage of the opamp. You increased the input impedance but the tone controls section must be driven from a low impedance opamp...
  20. audioguru2

    Is there a big difference between an FM transmitter and an FM receiver?

    A cheap radio overloads when the transmitter's signal is strong because it is nearby. The designer reduced the sensitivity of the radio so that it doesn't overload so much. Then it cannot pickup weak stations that are far away, and it still overloads but not as much. A good radio is extremely...
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