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  1. walid1

    a very simple FM Tx

    the following FM circuit I have tree questions: 1- what the function of the 1 n cap 2-why tapping the coil, why not connecting the antenna directly to the collector 3-what the function of the 1.8p cap, and why it is so small thanx
  2. walid1

    TV's and monitors maintainance and repair Forum

    i want a community (forum) like this electronic-lab community, where they discuss about  TV's and monitors maintainance and repair thank you very much
  3. walid1

    a low value wattage resistance

    hi in many many circuits u faced a wattage resistance for example in a PC monitor i see a 1 ohm 5 watt and in a low cost inverter in our project section you can see a 6 0.5 ohm 10 watt also in many car batt charger you find one directly before the batt why this resistance can i replace it with...
  4. walid1

    SMP power supply

    Hi In the Fig shown below is the input part of a switching mode ps as most of us know the 220VAC is connected directly to the rectifer (4 diodes) through a filtering network the rectifier o/p is about 310VDC in some SMPS there is a one main filter capacitor 400v 220uF or so in another there are...
  5. walid1

    What the meaning of .....

    What the meaning of hybrid i read the following in the STR50330 datasheets: Hybrid IC voltage regulator thanx
  6. walid1

    Infrared Remote Control

    Hi from this link:  http://home.maine.rr.com/randylinscott/aug98.htm Iread the following: The MOD accepts a 40khz IR signal that is modulated at 4 khz. When a signal is received the MOD will go low. The sensitivity of the MOD is set by different values for R1 and C1. from that I understand...
  7. walid1

    a very new Idea

    Hi my friend asked my help in his design he wants some sensors placed some where in a gate that counts the visitors come in or out. when the number inside the room is say ten, the gate must closed and prevent more people from inteing i tell him that he may use a controller like PIC16F84A and...
  8. walid1

    Broken Charger-connection Alert

    The circuit shown below is from: http://www.redcircuits.com/Page86.htm For me, it is easy to analys any circuit containing npn transistors, but i'm confused when come face to face with pnp type i read this in the same page: Circuit operation: The circuit is inserted between the supply...
  9. walid1

    a hi fi amplifier

    Hi I know what is an amplifier, but what the meaning of HiFi thanks
  10. walid1

    CM8870, DTMF Receiver

    (1) I read carefully the CM8870 datasheets but I can't conclude that it can     receive the FM signal directly or it must be connected to a separated FM     receiver please tell me (2) I hardly got the datasheets of CM8870/70C, but i really have CM8870PI     Is there any difference? thanx
  11. walid1

    simple question about batt chargers

    Hi all my friends When somebody build a batt charger that stop charging when batt full, he must use a comparator to compare batt voltage to some referance voltage.. when i conect a 3 volt batt to 5v power supply and wat to measure the woltage across the connection, what would it be? i ask...
  12. walid1

    Plants Watering Watcher-2 by Audiguru

    Hi all my friends, i miss you all, it is good to back In the Fig.plants1 shown below there is a part of the circuit, this part is the IC1-C work as 2 Hz osc. As the author said. Pin 10 is connected to 3v Vcc R3 = 3.9M R4 = 100K C4 = 220n D1 = any small signal diode The designer wants that the...
  13. walid1

    op-amp low frequency pulse generator

    I understand the 555 timer IC when used in its astable mode as an oscillator, but the one shown below i need some help in: (1) how this oscillator work? (2) the function of the diode? (3) how to choose the components values to achieve some freq.? (4) What the formula used to calculate the freq...
  14. walid1

    a regular transformer

    Hi I read this somewhere: "a regular transformer is designed to transfer energy from its primary to secondary and to minimize stored energy." Can someone please explain how they minimize the stored energy, that is what they do to minimize it? thanx
  15. walid1

    filter

    I want to learn
  16. walid1

    Resistance wattage in series

    Hi I analyze a timer circuit using transformerless power supply, that is no transformer, but a 330 nF in series with two 240 ohm 1/2 watt resistors. i noticed that the designer always use two-series 240 ohm 1/2 watt resistors. he do so three times in different places in the circuit. Also he...
  17. walid1

    Universal battery charger

    In the circuit shown below there is a Universal battery charger from: http://hem.spray.se/lythall/power/charger.htm it is easy to understand and to implement, but i have some questions: (1) Why u think the designer use the 4u7 cap. (2) If LM358 is used as a comparator, why:       (a) using...
  18. walid1

    Audioguru FM Tx

    Dear Audioguru, please can you lell me where can I find a full text about your FM Tx whose circuit is attached below. thank you.
  19. walid1

    C-E Amp circuit sim using spice

    I write the following prog to simulate the circuit shown in Fig.C-E below: common E Amp freq response VCC 7 0 DC 12 VS 1 0 AC 1 Q1 4 3 5 Q_2N2222A_N RS 1 2 1K C1 2 3 2uF R1 3 0 10K R2 7 3 30K RC 7 4 4.3K RE 5 0 1.3K C3 5 0 10uF C2 4 6 0.1uF R3 6 0 100K .MODEL Q_2N2222A_N NPN( IS=11.9F NF=1 NR=1...
  20. walid1

    C-E Amp circuit sim using spice

    I write the following prog to simulate the circuit shown in Fig.C-E below: common E Amp freq response VCC 7 0 DC 12 VS 1 0 AC 1 Q1 4 3 5 Q_2N2222A_N RS 1 2 1K C1 2 3 2uF R1 3 0 10K R2 7 3 30K RC 7 4 4.3K RE 5 0 1.3K C3 5 0 10uF C2 4 6 0.1uF R3 6 0 100K .MODEL Q_2N2222A_N NPN( IS=11.9F NF=1 NR=1...
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