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Type: Posts; User: IanP

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    Closed: Re: how to calculate Pull down resistor for 8051

    I don’t think you work with the “old” 8051, instead your derivative is more likely to be AT89S52, or something similar. They don’t have internal pull-up resistors, as resistors take up a lot of area...
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    Closed: Re: can a capacitor(s) crank a car?

    You can buy 150F @ 14V capacitor (build of 6 x 900F cells).
    Theoretically it should work, but I’d really like to see them in action ..
    :wink:
    IanP
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    Closed: Re: 89s51 interfacing with induction cooker coil

    Most of these circuits with IGBTs (or power MOSFETs) operate on the principle of PWM.
    Somewhere in the circuit there is a comparator working as a ramp generator, and somewhere in the circuit there...
  4. Closed: Re: 433 MHz ASK RF Tx Rx using 8051 UART

    Yeah, you have to invert data at both ends.
    Slow down the transmission to well below rated 4800bps.
    I'd go as low as 300bps, and then make sure you use at least a 2-byte sequence, don't relay on...
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    Closed: Re: Is this radio module enough for a remote relay?

    This radio-module has several GPIOs, so use one of them to drive a transistor and then a relay.
    The Rx and Tx pins are designed to trasnmit serial data ..
    :wink:
    IanP
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    Closed: Re: Voltage Buffer/ Follower without opamp?

    A follower(or a buffer) by definition has to have very low output impedance, as it has to drive any load.
    If for any reason you need to increase the output impedance, just add a resistor of a...
  7. Closed: Re: Design input 3.7V lithium battery , output 3.3Vdc, 100mA

    There is a range of 3.3 100mA (300mV)LDO regulators.
    Have a look at this example:
    http://www.linear.com/product/LT1761

    :wink:
    IanP
  8. Closed: Re: Quenstion about resistor around transistor(HELP)

    Before addressing your Qs lets make some obvious statements: in this application the transistor works as a switch ie. it replaces mechanical On-Off device. So it works in completely non-linear...
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    Closed: Re: how to use bd137 transistor

    Transistors are used for switching DC.
    For switching AC you should use a triac or a thyristor (SCR) …
    :wink:
    IanP
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    Closed: Re: Serial programming the DS89C450

    420 is not identical to 450.
    the software was right - you have to use the exact part number.
    :wink:
    IanP
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    Closed: Re: Solar Circuit Help Please

    The correct operation of this circuit relays on propers selection of solar panel, battery and LED.
    And it works like this:
    When there is no voltage generated by the solar panel, or the voltage...
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    Closed: Re: LM338 15A Power Supply Circuit - HELP please

    Resistors are characterized by their resistance and max power.
    That is enough to calculate max current and max voltage drop (in case you need to know it for something).
    You can apply...
  13. Closed: Re: taking too much current or voltage during start up any electronic device

    You can call this effect – inrush current.
    In all electronic devices you can find bigger or smaller storage capacitors that, as the name indicates, have to be charged first and that occurs when the...
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    Closed: Re: Help with instumentation amplifier

    For a quick test, I’d connect output with the (-) input for a gain (1) amplifier, and try it that way –from -9 to +9 with a potentiometer ..
    :wink:
    IanP
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    Closed: Re: 15 VDC 1000mA to 12VDC 160mA converter

    All what you need for the fan is to drop 3V, from 15V to 12V, assuming the 15V source is stable enough. If so, why not to use 4 standard 1N400X diodes connected in series, and as each of diodes drops...
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    [SOLVED]Closed: Re: Question about 74H4053

    Isw represents current per channel, not a total for all ... so +/-15mA shoulld be just fine ...
    :wink:
    IanP
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    Closed: Re: How to Calculate RC in IC LM555

    Goto:
    http://www.learnabout-electronics.org/Oscillators/osc44.php
    In this website you can find formulas and also a discussion on the 50% mark/space (duty-cycle) issue.
    :wink:
    IanP
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    [SOLVED]Closed: Re: Serial transfer not happening using Max232

    Try to test the loop: start with making a connection between pins 2 and 3 on DB9 and send a character via hyperterminal; it should echo it back to the screen.
    Then go one step further: connect pins...
  19. Closed: Re: Insufficient Current Output from 300V DC Adjustable Power Supply

    For some initial tests with small currents you can use that heatsink, but for real operation in the whole range of voltages it is way to small.

    I have attached a drawing that should explain the...
  20. Closed: Re: Insufficient Current Output from 300V DC Adjustable Power Supply

    You can remove the current limiting section of the circuit (R2 and T2) but you have to be aware that any short-circuit may end up with fireworks.
    I’d use R2 = 1ohm, just in case …

    As far as...
  21. Closed: Re: Insufficient Current Output from 300V DC Adjustable Power Supply

    Look, in this circuit ( http://www.oocities.org/tjacodesign/300vsup/300vsup.html ) current is limited by T2, and in particular by the value of R2.

    The rough formula for current limit in this...
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    Closed: Re: Can Inverters be op-amps?

    http://www.electronicspoint.com/ttl-linear-devices-t7353.html

    :wink:
    IanP
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    Closed: Re: Pulse shortening circuit

    Depending on the minimum width of the output pulse, you can consider 555 timer, TTL 74121, CMOC 4528,etc ..
    :wink:
    IanP
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    Closed: Re: USB to PS/2 keyboard converters

    Some keyboards are labeled USB/PS-2, and they have internal interface for both standards – it’s just the matter of the type of connector used.
    All other keyboards that are labeled USB (only) will...
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    Closed: Re: Relay Coil Spike Suppression

    1N4001 diode is far to slow.
    Use 1N4148 or similar fast switching diode ....
    :wink:
    IanP
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