Jump to content
Electronics-Lab.com Community

hotwaterwizard

Members
 View Profile  See their activity

  • Posts

    2,022

  • Joined

  • Last visited

 Content Type 

Posts posted by hotwaterwizard

  3. Dual LM3886 Bridged Amp.

    in Electronic Projects Design/Ideas

    Posted

    I think there is alot of difference between 30 watts and 50 watts. That is almost double! You can tell the difference between 5 watts and 20 watts so you can hear a big difference between 30 and 50 watts. The distortion of the amp is not the only concern when Bridging amps. They tend to run hotter as well. So the life expectancy of the IC will be Half of an Amp that has not been bridged.

  20. TDA9387PS Datasheet

    in Datasheet/Parts requests

    Posted

    [bTW I found a chinese site with lots of this chip but I can't navigate it.. :(
    http://www.hqew.com/stock/search.asp?KeyWords=TDA9387PS&imageField.x=7&imageField.y=16


    To Navigate this site is easier than it appears.
    See the picture of the little book in the minue bar?
    Click on it and a Search box will appear.
    Enter your part # there and push enter on your keyboard.
    It does a search for that part.
    Then a list will apear or it won't.
    If there are 0's in the line that appears then they do not have a datasheet for it.
    If a bunch of PDF icons apear.
    Try your luck and one of them may hit the jackpot.
    Most of the time it doesn't. Some times it will.
    If it does then you will get lost again.
    Look in the bottom right hand corner of the page and you will see a little picture of a computer.
    Just click the picture and the download will begin.
    There you have it.

  22. Weird relay problem..

    in Electronic Projects Design/Ideas

    Posted

    Info on false triggering:

    Copied from

    http://home.cogeco.ca/~rpaisley4/LM555.html

    "RESET" And "CONTROL" Input Terminal Notes
    Most of the circuits at this web site that use the LM555 and LM556 timer chips do not show any connections for the "RESET" and "CONTROL" inputs for these devices. This was done in order to keep the schematics as simple as possible.

    When the "RESET" terminal is not going to be used it is normal practice to connect this input to the supply voltage. This is especially true when the CMOS version of these timers is used as the inputs of these devices are very sensitive.

    In many cases the "CONTROL" input does not require a bypass capacitor when a well regulated power supply is used. It is good practice however to place a 0.1 microfarad or larger capacitor at this terminal.

    The venerable LM555 timer chip and its twin brothers the LM556 have been a cornerstones of model railroad electronics but the sensitivity of the trigger input gives rise to many false triggering problems. The addition of a 470K ohm resistor and a 0.1uF capacitor at the trigger input (Pin 2) will provide a time delay of 1/20th of a second from the time the input goes to zero volts until the trigger threshold is reached (1/3Vcc). This can eliminate false triggering in most cases and if the problem persists the size of the capacitor can be increased.

    The following schematic shows two additions to the basic 555 timer circuit. One reduces the trigger sensitivity and the other will double the output pulse duration without increasing the R1 and C1 values.

    LM555Helpers.GIF
    555 Timer Helpers Schematic
    The addition of a capacitor to the trigger will not work for short output pulses as there is also a short delay in the recovery of the trigger terminal voltage.

    The second 555 timer helper will extend the timers output duration without having to use large values of R1 and/or C1. By connecting a 1.8K ohm resistor between the supply voltage and pin 5 of the 555 timer chip the output pulse duration will approximately be doubled.

    To achieve long output times electrolytic capacitors are used for C1 and the value of R1 may be as high as 1 Meg. However with high resistance values for R1 the leakage current of the timing capacitor (C1) becomes a significant factor in the operation of the timer.

    The circuit will run much longer than expected and may never time out if the leakage current is equal to the current through the resistor at some voltage. Tantalum capacitors could be used as they have very low leakage currents but these are expensive and not available in large capacitance values.

    The boxed in area of the drawing shows the internal circuit at pin 5 of the timer with the 1.8K resistor added. The voltage at pin 5 will be increased from 0.66Vcc to 0.84Vcc which is equal to the voltage across the capacitor after two time constants. This allows the same output time to be achieved with a smaller resistance or capacitance value thus reducing the error caused by the capacitor leakage current. Conversely, for a given value of R1 and C1 the output time will be doubled. (One time constant is equal to R1 times C1).

    The trigger voltage level of the timer will also be increased with the addition of the resistor to pin 5 but this should have no effect for most applications.

    This is not an ideal solution to solving long duration timing situations but will be OK for times of less than five minutes.

    RESET And CONTROL Input Terminal Notes

×
×
  • Create New...