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  1. audioguru2

    Infrared Activated Switch

    Hi, Congratulations, Uncle! ;D  I thought I was the uncle around here. 1) In your 1st opamp, you have a single supply, but it is drawn like it should have a dual-polarity supply. Pin3 doesn't have a reference voltage so will float around 0V. Then the opamp will amplify the difference in...
  2. audioguru2

    help needed hooking up 4 lm3914

    Instead of dividing the output of the transducer to feed the cascaded LM3914's, usually the signal for the lower-level ones are amplified with an opamp for each one. The brightness of the LEDs for an LM3914 is determined by its reference current. A current sink at the reference output pin for...
  3. audioguru2

    Telephone Billing machine!!!

    What pulses? In my country, a long distance call sounds just like a local call without any beeps or pulses. A phone system in a hotel senses the "1 plus area code" at the start of a long distance call, waits for the call to be answered when the telco's battery voltage to the hotel's phone line...
  4. audioguru2

    Infrared Activated Switch

    IR radiation on a reverse-biased IR photodiode causes it to leak a tiny reverse-current. If you want a range more than a few cm then your circuit needs the gain of an opamp or two. You could try an extremely high value for the resistor that feeds the IR photodiode its reverse voltage. Then it...
  5. audioguru2

    Charging a 9V rechargable battery using two 9V dc Motors

    What is driving your motor/generators for 14 hours? Do you have a big waterfall and are using a gearing system so that they operate at more than their max RPM? Why do you want to use a DC motor as a generator? Just plug the battery into a charger in the evening and it will be fully charged by...
  6. audioguru2

    Charging a 9V rechargable battery using two 9V dc Motors

    Your 8.4V Ni-MH battery will be about 9.8V when fully charged. I don't think a 9V motor that is used as a generator can supply 27mA for about 14 hours at 9.8V or more.
  7. audioguru2

    Infrared Activated Switch

    A TL072 opamp has a voltage gain of 200,000 at DC and very low frequencies. Is frequency response is to 3MHz with a circuit gain of 1 and reduces to 1/10th for each increase in gain of 10. Therefore with a circuit gain of 100, its frequency response is to only 30kHz. With a circuit gain of 30...
  8. audioguru2

    Infrared Activated Switch

    Get the SFH2030F with the daylight filter. It has a much narrower pickup angle than the wide-angle Chinese one. Get a TL072 dual low-noise opamp confiured as 2 stages with a gain of about 30 each. Then you will have a home-made IR circuit similar to an IR receiver module without its important...
  9. audioguru2

    Infrared Activated Switch

    The calculation for R2 discharging the capacitor can be doubled, so would be 2 x (0.693RC), but since the output of a 555 doesn't go as high as +12V nor as low as ground then the frequency would actually be lower than calculated. You got a pot so just adjust it to the correct frequency. Sure...
  10. audioguru2

    Infrared Activated Switch

    The LM567 test circuit uses 0.0033uF (3.3nF) for C1, 0.005uF (5nF) for C2 and 0.02uF (20nF) for C3. Your 555 circuit is conducting about 90mA through its IR LED which is plenty. Of course the duty % changes because the cap is charged with 2 resistors but discharged with only one. This circuit...
  11. audioguru2

    Speakers

    I have taken 3 different RadioShack speakers that didn't sound too bad and threw-out their garbage cone tweeters, replacing the tweeters with good dome ones. Then I also threw-out their garbage single capacitor which was called a "crossover network" and replaced it with 2 coils, 3 capacitors...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    If the output is shorted of your project with its low unregulated supply voltage of only 31V, the internal chip of a 2N3055 transistor will operate with no margin for safety at its absolute max temperature of 200 degrees C, with an enormous heatsink of infinite size, with a very high velocity...
  13. audioguru2

    TSL220

    TI at www.ti.com won't send you a TLS220 because they haven't made it for a few years and don't have one. You can download its datasheet from their website.
  14. audioguru2

    Infrared Activated Switch

    Hi Hamoodyjamal, National Semi still make an LM567. Its datasheet shows the calculation for frequency and a test circuit. Just use their test circuit with a 10k pot adjusted about halway to replace their 2.4k resistor. I don't know if the Duty % reading of your multimeter is accurate at high...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi TA, It's good to hear that your vacation was wonderful. ;D It is fine to change the emitter resistors to balance the output transistors. If you want to feel some heat, turn up the current regulator and short the output. That will be when the output transistors should be matched. Almost the...
  16. audioguru2

    Infrared Activated Switch

    The SFH300 phototransistor is in a clear case and detects all light plus IR. A SFH300FA is in a black case which is an IR filter and doesn't respond much to visible light. A frequency as low as 200Hz is very close to double the mains frequency produced by mains-powered electric lights and would...
  17. audioguru2

    CMOS...floating inputs

    Hi Jrcfg, A Cmos input has an extremely high resistance and will: 1) Get damaged by any nearby static electricity. 2) Capacitively pick-up nearby signals resulting in a wrong or random output. 3) Maybe oscillate at a very high frequency if it picks-up its own output. 4) Dissipate power because...
  18. audioguru2

    Infrared Activated Switch

    Hi Hamoodyjamal, Aaron's IR receiver circuit is missing a very important 100k resistor from pin 3 of the opamp to ground. It doesn't have AGC so it is easily overloaded by ambient light and IR from sunshine. Its slow opamp can't function at 40kHz.  I don't know if a phototransistor can switch...
  19. audioguru2

    transistor question

    Bad transistors don't work very well, do they? Yes, as long as the transistor is rated for more than the current of the relay's coil. The transistor will need its own base resistor. Also, the relay's coil will need a diode across it to arrest the very high voltage created by the coil when its...
  20. audioguru2

    transistor question

    OOOps, Boy, did I ever get it wrong, a second NPN transistor is needed to turn-off the LED driver transistor so that the LEDs will light opposite of one another.
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