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  1. audioguru2

    Latching comparator help

    A high resistor value will cause an input offset voltage error due to the opamp's input bias current. A high amount of filtering will cause a delay. The base of the transistor would be damaged by too much reverse voltage if its emitter had a capacitor or something to hold a high voltage. The 741...
  2. audioguru2

    EL WIRE---if you know anything about it click here!!!URGENT...sorta

    You should use 12V. You say that with 13.5V its frequency is higher, so then the inverter uses more current and is strained. Connect two 1N4002 diodes in series with the power supply's 13.5V output to get 12V. Since you are using less wire then the power supply isn't at its rated current and its...
  3. audioguru2

    CRITISIZE THESE CIRCUITS

    Hi Musty, Pin 8 is the 555's Vcc pin and pin 4 also connects to Vcc if you don't want a reset. Your schematic shows them correctly. Your 555 is missing a couple of supply bypass capacitors connected very close to pins 8 and 1. The 555 has a high power output which draws a supply current spike of...
  4. audioguru2

    CRITISIZE THESE CIRCUITS

    Hi Musty, Most 555 manufacturers have an error on their graph for a monostable's timing, so I looked in Signetics databook, its inventor. No graph but the same formula as everyone else: t= 1.1RC, which is 11ms. It won't time-out if the trigger pin is low just before and during time-out. ;D
  5. audioguru2

    EL WIRE---if you know anything about it click here!!!URGENT...sorta

    An ohm-meter will quickly show if the wires in the EL glow-wire are shorted at a sharp bend. LiveWire says to never make sharp bends in their EL glow wires.
  6. audioguru2

    op-amp low frequency pulse generator

    Oops, yes. Yes. The output transistor inside the comparator is an NPN transistor with its emitter at the negative supply and its collector at the output pin. Pin 6 never gets to ground. C2 charges and discharges between 2V and 4V. R3 causes positive feedback for a snap-action of the comparator...
  7. audioguru2

    EL WIRE---if you know anything about it click here!!!URGENT...sorta

    Hi Um, I think you blew-up the inverter. It has only about 4 transistors so maybe you can fix it. The smaller wrap wire could burn-out if the EL wire got shorted at a bend in it. EL wire slowly gets permanently dimmer if the current or frequency is too high.
  8. audioguru2

    security system project

    Hi Buddie, Welcome to our forum. ;D Hardware stores have a pretty good PIR motion detector sensor that can trigger an alarm of your choice. At work, they got a wireless PIR motion detector with a wide sensing span and a range of about 10 or 15m. Its wireless range was far. It was from...
  9. audioguru2

    i need a little central circuit?

    Yeah, if you get two phones that have hold buttons on them, you can connect buzzers/buttons on the spare pair of the wire between the phones, to alert the other phone that a call is for them. I got a cheap phone with a hold button. It plays awful Chinese music on hold that repeats over and over...
  10. audioguru2

    in search of a FM STEREO transmitter

    Hi Alexander, Welcome to our forum. ;D Just now, I went to Google (link at the bottom of this page) and in the search box entered Silicon Chip Micromitter. The 1st link was the entire article for free. My browser is IE6 and I didn't need to delete cookies or anything.
  11. audioguru2

    i need a little central circuit?

    What is a central? What do you want to do with the two phones?
  12. audioguru2

    Is it possible to build a tranceiver on am with mhz

    Where's the moderator? Oops, there isn't a moderator anymore, I guess anything goes. ;D
  13. audioguru2

    Speaker - frequency and impedance

    A speaker has such a low capacitance that its electrical resonance must be extremely high, maybe RF. Didn't I mention that: "A resonating speaker is a generator". Short a generator and see how hard it is to move it. Try it. Spin a DC permanent magnet motor. It spins. Then short it and try to...
  14. audioguru2

    Speaker - frequency and impedance

    Sorry, Walid. We were talking about a speaker's impedance (it is an inductor so its impedance is higher at high frequencies) and I mentioned a speaker's mechanical resonance. Speakers have a low frequency mechanical resonance. At the resonant frequency, a speaker's cone  vibrates freely with...
  15. audioguru2

    op-amp low frequency pulse generator

    Sorry, Walid, I didn't notice your 6V battery. Here is my reply corrected for a 6V battery. The negative of the battery is the circuit's "ground". Quote from: walid on January 12, 2006, 12:01:46 PM (1) pin 5 always connected to the voltage divider formed by R1 and R2 and so it is always at 3v...
  16. audioguru2

    C-E Amp circuit sim using spice

    Hi Walid, Doesn't your sim program have built-in spec's for common transistors? A typo can mess it up. The sim program works with "typical" spec's. The actual results with "real" transistors having a wide range of current gain and Vbe will be much different. Change the current gain in the...
  17. audioguru2

    CRITISIZE THESE CIRCUITS

    Hi Musty, The 4A fuse following the regulator is way too high. It isn't needed anyway since the regulator will current-limit if the current reaches 1A to 2.2A, and shut-down if it gets too hot. The resistance of the fuse ruins the voltage regulation. The regulator doesn't need the huge capacitor...
  18. audioguru2

    darlington power amplifier transistors

    Hi Leo, My multimeter has a Diode Test function where it outputs a small current then shows the voltage. A darlington's forward-biased base-emitter would show about 1.2V. Reverse biased would show max volts. Forward-biased base to collector would show about 0.6V. Reverse-biased would show max...
  19. audioguru2

    Input signal for LM3915. need help.

    Yes, but they have different pin numbers.
  20. audioguru2

    current series feed back in amplfiers

    Hi Zeppelin, A transistor stage without negative feedback has horrible distortion. Its gain is very high but the high distortion makes it unusable and impossible to measure. Here is a circuit with parts values that I simulated:
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