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  1. audioguru2

    circuit help

    Hi Steven, Your circuit is exactly the same as the output section of my Electronic Stethoscope-2 project, and the same as on the LM386's datasheet. The only difference is that it doesn't have enough gain. Connect a 10uF cap between pins 1 and 8 of the LM386 with its positive wire at pin 1. I...
  2. audioguru2

    tv antenna enhancement

    Hi Aselsus, Maybe your TV's antenna is too low to pickup an obstructed signal. A directional antenna or amplifier probably won't help if there is no signal to receive. The TV already has a very sensitive tuner and more amplification will just pickup more noise and interference since the TV...
  3. audioguru2

    Voltage Multiplier

    OOOps, You could propel the bike and tow a huge trailer for weeks if AA cells were rated at 2200A/hr. They are actually 2200mA/hr. Sorry.
  4. audioguru2

    Voltage Multiplier

    Hi Clark, I am sorry that your generator project didn't work. But I am glad you realise that if the fan was large enough to create the same wind-resistance to your cycling effort as a mechanical dynamo, then you wouldn't gain anything. I am also glad that you realise the huge size required for...
  5. audioguru2

    lightbulb's role in car amp

    Hi MP, I'm glad that you realised your error in explaining the temperature affect on the resistance of a light bulb's filiament. I just measured the resistance of some 100W, 120V bulbs. They should be 144 ohms, but measured only 9.8 ohms when cool. That is a 14.7 times difference! If the bulb...
  6. audioguru2

    simple amplifier circuit.

    Hi Chrono, In your 1st circuit, the transistor is turned-off all the time because it doesn't have base bias current. When you managed to get it working, its output must have been extremely distorted because the transistor would have conducted only during the very loudest positive-going peaks...
  7. audioguru2

    lightbulb's role in car amp

    Hi MP, I'm sorry to correct you. Actually, the resistance of a bulb's filiament increases when it heats up (like most metals). Its resistance when cold could be as low as 1/10th what it is when hot. That is why a small transistor would fail when driving a lightbulb that is within its current...
  8. audioguru2

    Low-pass Filter?

    Hi Kevin, A 20VAC center-tapped transformer secondary winding is usually written like this: 10-0-10. The "0" is usually the ground, and the "10" at each end of the winding are of opposite phase. You can make a full-wave rectifier with a center-tapped winding by adding only two diodes, in series...
  9. audioguru2

    timer relay circuit reqest

    Hi Steven, All you need is a 555 timer IC wired as a monostable like in our Articles section. A momentary pushbutton shorts its pin 2 to ground to start the timing and a resistor and capacitor on pin 6 determine the time period. Connect pin 7 also to pin 6. Its output can drive a relay coil with...
  10. audioguru2

    Re-called Light Bulbs

    Aren't they all the same now and made in the same factory? This box to Philips, that box to Ikea, the box over there to GE, etc.
  11. audioguru2

    More IR help!

    Hi Stuee, Your heat-lamp load is 3200W, correct? Sorry, I can't get your long links to work.
  12. audioguru2

    Re-called Light Bulbs

    Hi Ante, I agree with you that prices vary a lot. Today I went to see the changes on new cars. Again, the salesman was very hungry for my business (it is near the end of the month). Guess what! ......................... ;D 8)
  13. audioguru2

    Plants Watering Watcher-2 project

    Hi Guys, Update: The project is here: http://www.electronics-lab.com/projects/science/018/index.html The AAA alkaline battery cells on the first two units that I made more than 5 months ago have dropped below 1.0V each. The units were still flashing brightly. The batteries didn't last as long...
  14. audioguru2

    More IR help!

    Hi Stuee, Don't use resistors to reduce the power to the heat lamps. The resistors would heat as much as the lamps! Hundreds of Watts. Just use a lamp dimmer. Make certain that it is rated for the load. Restaurants use high-power rated dimmers. What is the heat-lamp load? Your pic shows 8 X 80W...
  15. audioguru2

    Voltage Multiplier

    Hi Clark, Thanks for the link of the guy producing 64,000V! Where's Steven? That guy doesn't care about the voltage drop across his diodes. You might not need a voltage multiplier and its losses if your dynamo produces 8V when you blow it enough to get dizzy. Your meter probably measures AC RMS...
  16. audioguru2

    Who is using the oldest computer?

    Hi Ante, At work I always sent a PCB request out to a "PCB Pro" company. They would lay it out then make 20 for me to try before full production. Years ago I saw a PCB layout program draw a single straight line then about 20 lines that went around it. I would have drawn 20 straight lines and use...
  17. audioguru2

    Re-called Light Bulbs

    Hi Ante, Sure we have Ikea stores here. Graduating students like their modern designs and inexpensive furniture. Cheaper stores use the "bait and switch" selling technique. They advertise something at a very low price. They only have a few, or hide them so that shoppers buy other things at full...
  18. audioguru2

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

    Hi Ante, You charge your batteries at a very low safe current and use voltage limiting. I was cautioning Kain because he didn't understand that a current regulator will increase its output voltage to maintain the set current. He also misunderstood that a fully charged battery would automatically...
  19. audioguru2

    Potential divider

    Hi Gugh, Perhaps you will understand the operation of a voltage divider if you use extreme values for the resistors. Change the lowest value resistor to a dead short. Then change the highest value resistor to an open circuit (extremely high resistance) Now when you connect your voltmeter to its...
  20. audioguru2

    Voltage Multiplier

    Hi Clark, I am sorry to have sounded so pessimistic about your idea, but I don't think a 4" fan will provide much power at bike speeds. When you said you needed 350mA at 10.5V to power a 42-LED traffic light, I didn't realise that your Ni-MH rechargeable battery will be supplying most of the...
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