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  1. audioguru2

    Infrared Receiver

    Why make an opamp when they are inexpensive? A TL072 is a dual low noise opamp. It can be set with a gain of 100 for each opamp for flat response to 40kHz and a total gain of 10,000. An IR receiver module for a TV has all the circuitry that you need>
  2. audioguru2

    Making a 0-28VDC@0-3A Power Supply using linear regulators (LM350)

    Hi Niksun, You forgot to show where the load connects on your meters schematic. I think it is the LO terminal of the A meter. I don't know why R3 is in series with the voltmeter. Now it current-limits only when the LM317 has its max of about 2.2A, or when it gets too hot and shuts down. The...
  3. audioguru2

    Some angel out there!! need help for motor speed control by pll

    Hi Kellie, You have the feedback which is your VCO output connected to pin 3 of the phase detector instead of pin 5. Then pin3 needs a resistor to ground. You grounded the pin4 output which might have destroyed the IC.
  4. audioguru2

    project help with toy IC boards

    Hi Sukhbinder, I use LM390 audio amps in my clock radio and in a signal generator. It is too bad they have been discontinued for 10 years. They are like an LM386 but with a higher output current and bootstrapping of the driver transistor for a much higher voltage swing. Its minimum supply is 4.0V.
  5. audioguru2

    Inverter Circuit 12V DC to 230VAC Sine Wave

    Hi Grateful, 4.9kHz is very low for PWM. Your transformer will whistle loudly. Usually a frequency higher than 20kHz is used so it is not audible. An RC filter will waste a lot of power. Use an LC filter like class-D audio amplifiers use. The cutoff frequency of a circuit is the frequency...
  6. audioguru2

    Reducing 6.4V 2,700mah for a pda (ext battery)

    A diode in series is 0.3V with hardly any current, just a voltmeter as its load. With a few hundred milliamps its voltage drop is about 0.7V. With a 2A load it is about 1V. I thought you connected 5 diodes in series then connected them across the 6.4V battery to drop the voltage to 5V and to...
  7. audioguru2

    Reducing 6.4V 2,700mah for a pda (ext battery)

    Hi Explorador, Welcome to our forum. ;D First you say its max voltage is 5.0V, then you say its adapter is 5.9V. Which is correct? What chemistry type is the battery? Its voltage isn't Ni-Cad or Ni-MH which would be 6.0V for 5 cells. It isn't Lithium which would be 7.2V for 2 cells. Is it...
  8. audioguru2

    Infrared Remote Control

    Hi Walid, Radio Shack doesn't have the specs for the MOD anymore so nobody knows what it does. Maybe it is just a photodetector that responds to any frequency of IR, then R1 and C1 filter its output.
  9. audioguru2

    Making a 0-28VDC@0-3A Power Supply using linear regulators (LM350)

    Hi Niksun, Turn the 50 ohm pot down to 1 ohm for 1.25A output. It will dissipate 1.56W in only 2% of its physical resistive track. 100% of its track is rated for 5W so you will need to investigate how well it can dissipate heat from only 2% of its track. A 20 ohm/4W pot will dissipate 1.56W from...
  10. audioguru2

    VU meter

    Which resistor, its input level pot? It needs a pretty high signal level, 0.65V peak which is 460mV RMS. You should amplify its input with a preamp like they show. The circuit is missing a resistor across the PNP's base-emitter to turn it off. Try 100k. Maybe your input wires are not shielded...
  11. audioguru2

    What does this mean???

    Most semiconductor manufacturers use "CD" as a prefix to their Cmos logic ICs. So a CD4017 is an ordinary 4017. A Motorola MC14017 is also an ordinary 4017. Also, most Cmos logic ICs have a suffix of "B" to show that they have Buffered outputs, since the original ones weren't buffered.
  12. audioguru2

    Making a 0-28VDC@0-3A Power Supply using linear regulators (LM350)

    Hi Niksun, Your LM317 power supply design is much better. For up to 1.5A output, R1 will be set to 1.25V/1.5A= 0.833 ohms. A tiny portion of its resistance track will dissipate 1.9W, get extremely hot and maybe burn. Therefore R1 must be a wire-wound rheostat rated to carry 1.5A at low...
  13. audioguru2

    project help with toy IC boards

    Hi Sukhbinder, The TDA2822M is much better than the MC34119 at low voltages. It gives an output of typically 220mW bridged into an 8 ohm speaker with a 3V supply and with very clipped 10% distortion. As the battery runs down the power will become less and the distortion will become higher.
  14. audioguru2

    need help for cfl lighting

    Where are you going to buy an 8V-0-8V transfomer that has an extra feedback winding? If the turns on the extra winging are not enough then the inverter won't start, If the turns are too many then the transistors will blow up.
  15. audioguru2

    DC to AC

    Yes, AN920. That is what it says. That is also what I said. Also, notice in the block diagram that it uses an inverter to make the compliment, not the divider. The digital divide-by-two divider has a single output.
  16. audioguru2

    DC to AC

    The datasheet says clearly exactly what I said. I even explained how the IC uses a digital divider to make two of its outputs perfect square-waves.
  17. audioguru2

    VU meter

    In the VU meter project at Talking Electronics, the PNP transistor, diode, input capacitor and collector capacitor make a Half-Wave Peak Detector (rectifier circuit) with a fast rise time and a longer release time of its storage capacitor. Then each LED lights long enough that you can see its...
  18. audioguru2

    DC to AC

    The CD4047 has 3 outputs: 1) Its oscillator output which is an ordinary Cmos oscillator and they say "a 50% duty-cycle is not guaranteed". Inverter circuits don't use it. 2) a Q output at half the oscillator frequency and they say "at 50% duty cycle". 3) A Q-not output at half the oscillator...
  19. audioguru2

    VU meter

    Hi Mik3ca, Your circuit doesn't have a current-limiting resistor between the transistors. So when the PNP has a high input level then its collector current is unlimited and one or both transistors will blow up if the battery can supply enough current. I don't know why you have a filter...
  20. audioguru2

    DC to AC

    A series of opamps won't do anything. Their max output current is only 20mA. Mosfets switch very quickly. The CD4047 or the opamp switch slower and might cause both Mosfet sides to conduct at the same time. Investigation is required. Many things like current and heat dissipation specs and spike...
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