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  1. audioguru2

    I have been thinking

    I have a fairly simple extremely low distortion tone generator circuit. I tried to make it sweepable with a 74HC4046 PLL but phase jitter ruined its low distortion. It has a fixed 400Hz frequency now. Its matching distortion analyser circuit is very stable, has the proper high Q and is pretty...
  2. audioguru2

    sensitive parabolic michrophone

    This circuit:
  3. audioguru2

    LED FLASHER

    Yes and no. R1 limits current through the LED and determines the very fast charge time of C1. The slow RC time that C1 is discharged by R3 plus the RC on the other side determines the timing. When C1 has finished discharging by R3 then it begins charging in reverse by R3 when Q2 turns on. Only...
  4. audioguru2

    7447, 7448 decoders

    I couldn't find a datasheet for your display. If your 5V supply is actually 5.25V and the LED display is actually 1.8V then 300 ohms (lower if 5%) will cause a display current higher than the max of the display. Use 330 ohms.
  5. audioguru2

    Op amp theory Q's

    A good amplifier has a bandwidth much higher than we can hear because ultrasonic frequencies intermodulate if the ultrasonic distortion is high, causing beat frequencies that we can hear. Some people "claim" that some opamps sound better. I know that LM324 (LM358 dual) and 741 opamps sound...
  6. audioguru2

    7447, 7448 decoders

    Hi Autir, The '48 has pullup resistors and lower output current since it is designed to drive logic gates, not LED displays. The '46 and '47 have an output current of min 40mA. Don't you think your display with a 10mA rating will be destroyed without current-limiting resistors? You could...
  7. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, who me? I'll make a detailed circuit description of the circuit after we get your breadbord circuit working. It doesn't use radio frequencies so if the contacts on your breadboard work then the circuit should work. C2 and C3 are parts in a bandpass filter. Their tolerance should be as...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Rodrigo, It is time to troubleshoot your project: 1) Remove R15 (1k or 100 ohms), R12 (56k), C6 (100pF) and C9 (100pF). 2) Temporarily connect the 56k resistor where C9 was. 3) Turn on the power without a load and measure if the output pin 6 of U2 goes smoothly from 0V to 35V when the voltage...
  9. audioguru2

    500W 12v to 220v Inverter

    Hi Doron, The inverter draws about 50A from a 12V battery when it has a 500W load. 41.7A for the load and the rest for heating itself. Without a load or when starting without a load, the current from the battery is probably only 2A if the transformer is good. The gain of transistors depends on...
  10. audioguru2

    Help....

    There are many types of optocouplers: transistor, Schmitt-trigger logic, FET. You are probably using one with a transistor output. The transistor is linear so its output voltage depends on the strength of the IR beam that is shining on it. If you want the transistor to conduct hard then shine a...
  11. audioguru2

    Help....

    Your IR distance sensor is the same as an optocoupler. The difference is that distance causes the phototransistor to receive less IR because the IR beam spreads out and therefore its energy is divided over the wider area.
  12. audioguru2

    sensitive parabolic michrophone

    An LM386 little power amplifier IC has a gain of up to 200. Its circuit is simple, it is cheap and amplifies an electret microphone very well.
  13. audioguru2

    FM/AM transievers

    Hi Elven, Compared to my Sony Stereo Walkman AM-FM radio, the TDA7021T is lousy. It is noisy, very distorted and has poor selectivity and poor audio frequency response. I have two Chinese copies of Philips' earlier IC in scanning FM radios and their performance is terrible. They cost $1.00 in...
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Rodrigo, Check the pins on Q2 or Q4. If its base is connected to +30V where its collector is supposed to be then the output voltage will stay at max.
  15. audioguru2

    wireless LED circuit design

    In Google, I entered IR Remote Control Circuit. The 1st link is full of circuits: http://www.discovercircuits.com/R/remote.htm
  16. audioguru2

    wireless LED circuit design

    Hi Steev, Your LEDs each need 3V. Therefore 4 in series need 12V. Right? Wrong! LEDs need a current-limiting resistor in series to limit the current. The resistor needs voltage in addition to the voltage needed by the LEDs. Therefore you need about 18V to light four 3V LEDs in series. An 18V...
  17. audioguru2

    500W 12v to 220v Inverter

    Hi Doron, Welcome to our forum. ;D What don't you understand about the simple inverter? 1) It uses a CD4047 Cmos IC as its oscillator. It has a frequency divider inside to produce perfect square waves. It has two outputs and one is inverted so their voltage waveforms are opposing. 2) The opamp...
  18. audioguru2

    wireless LED circuit design

    The circuit's LM567 PLL tone decoder has a min supply voltage of 4.75V and a high operating current so this circuit is ruled out. Very bright green, blue and white LEDs need a supply voltage of at least 4.5V so they are also ruled out. 5 ordinary LEDs use a lot of current which requires a fairly...
  19. audioguru2

    wireless LED circuit design

    Hi Steve, Welcome to our forum. ;D That faulty project is also on our site: http://www.electronics-lab.com/projects/motor_light/030/index.html It won't work properly unless a resistor is added from pin 3 of the opamp to 0V, as its reference DC voltage. Use 100k to 1M. The old LM308 opamp isn't...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Rodrigo, The input voltage to U2 should change smoothly from 0V to about 11.2V from the voltage adjust pot. Without a load, U2's output voltage should change smoothly from about 1.2V to about 36V (if the supply voltage is high enough) since Q2 and Q4 are emitter-followers and since R11 and...
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