Jump to content
Electronics-Lab.com Community

Shahriar

Members
  • Posts

    451
  • Joined

  • Last visited

Posts posted by Shahriar

  1. Good Points  ;)
    ThanK you very Much for Your reply.


    Also take a look at this site. It is really fun. Althoght you may have seen it before. ::)

    http://www.linkwitzlab.com

    In fact I do not understand very much from those equations, But I really enjoy the Pictures  ;D Specially:

    http://www.linkwitzlab.com/Pluto/photos.htm
    http://www.linkwitzlab.com/orion_us_examples.htm

    Shahriar

  2. Hi

    Look at this LoudSpeaker
    http://www.roundsound.com/reference-3-speakers.htm

    Two Things are dark to me:

    1- Is the back of those Speakers Open or Closed. Specially the Woofer? If they are closed, Are they sorrounded with the Round Cabinet
    or there is a air way between the cabinet and The Main Black Chasis?

    2- The two small one Speakers seems to be the same? are they really the same or One of them is Tweeter and the Other one is a midrange? or they are the same but with different Cross-Over circuits?

    ThanX in advance
    Shahriar

  3. Hi
    I was Looking in Audio Project section and I encountered with this Project (Motorola Hi-Fi Power Amplifier)
    http://www.electronics-lab.com/projects/audio/041/index.html
    Something is strang to me. The output voltage is always equal to OpAmp Output. The Maximum
    output Swing for Opamp is limited with R3 and R4 to (Vcc/2 - 0.7V) . So the output power will be 1/4 of the
    Rated powers in Table, which I think is calculated with respect to Maximum swing of Vcc.

    1- Tell me if I am wrong.
    2- What better OpAmp do you know with Maximum Vcc of +-30V (741 is a little bit Old)


    ThanX
    Shahriar

  4. Last year I built this project for one my friends.

    Look at the attached files

    I also attached a SILICON CHIP files too. But I couldn't find the sensors in this project.
    Just remeber to keep the sensor  some where to protect it from Lamp Light.
    Otherwise you will  receive a 50Hz pulse at output although some filters have used to remove it.

    I used the sensors on  both sides but silicon put them in one side.

    HTH - Shahriar

    HearRate_Monitor_Schematics.rar

    SILICON_Heart_Rate_Monitor.rar

  5. Hi

    I have designed this power amplifier. I think it is a little bit different with Normal
    PA, because I have tried to use two Voltage-Current converter to drive power output
    transistors to reduce zero-crossing.
    I have attached the schematic to tell me anything wrong about the topology I have used.
    I have not draw all things needed in details. Just about Topology.

    Let me explain a little more:
    the Input signal will be converted to Current around U1A and U1B. (one Sink current and one Source current)
    a feedback is there around R7 & R13 to set the total gain about 40.

    1- if the input voltage is greater than zero U1A and q3 sink current from the base of Q1. I(sink) = Vi/R5)
    2- if the input is negative U2A and Q2 source current. Isource = Vi/R7
    3- U2A veries the voltage to control the output current through speaker.

    The Marked resistor values (R5 & R8) will be determined depending on desired Output power and speaker ohms.

    ThanX in advance
    Shahriar

    CurrentPA.pdf

  6. Dear $@$

    sometime ago I decided to build a line follower robot by a small camera.( Not a Web cam.)
    I had decided to detect between the black Line and the white background by proceesind the video sinal. and to position it by other pulses in a component video signal.

    U should have enough information about a video signal to understand what I mean.

    Although i didn't the job, But I still think it is possible to do such thing very easily. It has many benefits to using a sensor. meybe u can use suck tricks to recognize wall  depending on your conditions.

    HTH - Shahriar

  7. Hi

    I want to build this Active 3-way cross-over circuit.
    But I do Not kow how to choose Power amplifiers. Here the problems:

    1- If I choose a 15W subwoofer and a 15W STK power Amplier (STK4121) for it then what kind of Midrange and tweeter will be needed?
    Does it mean I have to choose a 15w Midrange and a 15W tweeter?

    2- Should the gain of all PA be the same? i.e. if the Midranges are

    8Ohm and Subwoofers are 4Ohm, how to choose the gain of PA?

    ThanX in advance
    Shahriar

    post-1483-14279143182281_thumb.jpg

  8. Hi
    I am trying to repair Some ATX power Supplies.but some of them do not have ordinary faults. Most of them are in these two categories.

    1- The computer assembler told me that with this bad PS, computer is working well but after a while (i.e. 10 Minutes or more) it will resets. but when they have replaced the ATX power supply, the problem was solved. Where should I look for this problem in ATX?

    2- Some ATX power supplies will cause the mother board to fail. I was wondered to hear this because of the Over Voltage Protection circuit in ATXs, but I think maybe the Factory has removed those circuits. My question: Is it possible such thing in case of a OverVoltage protection circuit?

    3- When I repaired an ATX, how can I test whether Over Voltage protection (OVP) circuit works to prevent MotherBoard Failing?

    ThanX in advance
    Shahriar

  9. Hi
    Look at the this OLD ATX power supply.
    Can somebody explain how the 3.3V regulatosr built around TL431 IC works. It looks like a
    Shunt regulator but very strange. I know How TL431 works but can't understand this circuit. i.e. if Q13 Current changes, how does this affect 3.3V rail. (look at R71)

    http://www.4shared.com/file/4564161/afd71557/atxps.html

    ThanX
    Shahriar

  10. Look what another guy has said about this topic:

    ESR is usually something to be minimized in a capacitor. However, where the original design depended (probably
    by accident) on a certain ESR, this may not always be the case:
    (From: Lee Dunbar ([email protected]).)
    Substitutions of low ESR caps into circuits which had lousy caps is not always the good idea that it appears to
    be.... Caution is advised, as low ESR caps will not limit surge currents.
    The circuits' series impedance drops (compare substituted capacitors ESR when new with the original capacitor's
    ESR was when it was a new capacitor), which, in turn, lets the surge magnitude rise, the higher currents destroy
    can semiconductors and other components.
    I guess what the industry needs is a good capacitor cross reference guide for aluminum electrolytics!

×
  • Create New...