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  1. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, I wouldn't say that higher frequencies have lower noise, just that they have less interference.
  2. audioguru2

    in search of a FM STEREO transmitter

    Hi Ras, I hope that you like the Micromitter. Please let us lnow what it sounds like. For the short distance between rooms of your house (you don't have a mansion?), its 10mW should be fine, it will probably go about 100m outside to a good FM receiver. 100mW will probably go 400m, 1W maybe...
  3. audioguru2

    Warning Light

    Hi Robert, Welcome to our forum. I was going to tell you where to stick the LED (he, he) and how to wire it, then realized that you shouldn't tamper with gas controls, it's dangerous and should be done by a certified gas fitter. My idea would be very simple but might make the gas valve stay open...
  4. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi King (your majesty, he,he), Sure, 4 transistors will be cool and look cool too. But only if you fasten sunglasses to them! 8) 8) 8) 8)
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Dosster, Welcome to our forum. I shop at www.newarkinone.com and www.digikey.com . I entered Hammond Power Transformer into Newark's search, selected Torroidal type and found a deluxe 30V/4A transformer with dual primaries and secondaries. They have less expensive ordinary ones too. Shipping...
  6. audioguru2

    VOX is not working - any help?

    Hi Con, I don't know why your IC was at a high temperature before. Maybe your electret mic has long wires and needs a shielded cable. Modifications for electret mic: 1) Relace C1 with a metalized-plastic 0.47uf/63V cap. 2) Connect terminal B to terminal C. 3) Add a 10K resistor from terminal A...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Thomas, There is very little difference beween the improved 3A project and the 5A one. The 5A supply requires a 30V/7.1A transformer, three 2N3055 transistors and its current sense resistor's value is reduced. Same OPA445AP opamps.
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Thomas, It is great that you can add a winding to the transformer to step-up its voltage. You aren't changing it much so don't worry about core saturation of additional temperature if the wire is the correct size. The project's max output current must be derated according to the transformer's...
  9. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, I don't know about RF noise. I just know that noise doesn't affect the VHF, UHF, microwave and visible-light frequencies that I use. I have never purchased "bandwidth"except for the high-speed-cable that connects me to the internet. Its bandwidth is about 50 to 100 times as much as...
  10. audioguru2

    VOX is not working - any help?

    Hi Con, The LM358 should be cold in this circuit. Is it installed backwards? It should have a notch on top on the end between its pins 1 and 8, or a dent on top beside its pin 1. Is the battery installed backwards or was it ever? If the IC or battery was ever installed backwards then the IC is...
  11. audioguru2

    LED light array with delay

    Hi Rob, A capacitor won't turn on an LED and keep it on. You need ICs to control the LEDs. Now you want the LEDs to turn on sequentially and stay on. A fairly simple way would be to use LM3914 ICs connected in the bar mode. You would have a capacitor charged linearly from a PNP transistor...
  12. audioguru2

    question about variable resistors??

    Hi Prateek, Dimmers control the brightness of more than one lightbulb by connecting all the bulbs in parallel.
  13. audioguru2

    FM WAVE PROPAGATION

    Hi Prateek, I don't think microwave and UHF satellite TV and cell phones are noisy. My 900MHz wireless phone isn't noisy. Even the 100MHz VHF FM band isn't noisy. They all work perfectly. My cable TV company sends signals 6000km using light frequencies (fiber-optics) and my reception is perfect...
  14. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi King (your majesty, he,he), It is good that you are using three 2N3055 transistors so they share the heat. Your 0.22E resistors will have a voltage drop of only 0.25V and dissipate 0.3W when your project is loaded to 3.5A output and will be fine. Good luck. ;D
  15. audioguru2

    heartbeat detection

    Hi Bluebird, I posted this electronic stethoscope project for listening to heartbeats: http://www.electronics-lab.com/projects/science/019/index.html
  16. audioguru2

    LED light array with delay

    Hi Rob, Welcome to our forum. 74HC4017 ten-output counter/decoder ICs could be used with many gates and flip-flops. 74HC4051 eight-output multiplexer ICs could be used with a 74HC4060 oscillator/counter and some 74HC4040 counters could be used with a few gates. The 74HC family can provide up to...
  17. audioguru2

    Telephone Ring Delay

    Hi God (really?), Welcome to our forum, I think the operation of a FAX/modem is opposite to what you need. When the modem is idle, the phone-out connects to the phone line. Therefore all your phones will ring immediately. If the modem is programmed to answer on the 2nd ring, it will...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tedy, Where on earth are you that you can't get common Texas Instruments/Burr-Brown opamps? You could try MC34071P opamps that are rated at 44V or another TLExxxx listed in this thread. With a 24V transformer unloaded, the total supply to the opamps will be about 42.4V. The little 2N2219 in...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Thomas, Welcome to our forum. 1) If your transformer's output is only 20.5V when loaded, then this project's max output voltage when loaded will be only about 20VDC. 2) Your big filter caps are fine. 3) 20.5V times the root of 2 equals nearly 29V. The transformer's 120W rating divided by 29V...
  20. audioguru2

    FM WAVE PROPAGATION

    Hi MP, Sorry, I don't know where the circuit came from. It might be very old and its author might not even still be alive. After all, I built the same kind of circuit 42 years ago. I was just helping someone who found the circuit and built this monster:
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