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  1. Closed: Re: Is there a safe way to fix this scratch on the hot side of PSU?

    Dell PSUs are no better or worse than every other make.

    Top picture: not much you can do to restore the original copper, I think I would run a wire link between adjacent solder pads along the...
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    [SOLVED]Closed: Re: Back EMF Diode Configuration

    HardwareChap - can you give us more information please.
    Are the two coils part of a single inductor (magnetically coupled) or are they independent coils. It makes a difference to the way the...
  3. Closed: Re: MCPCB which is double sided and with plated through vias

    Agreed - and what are the 'J' references to?

    Brian.
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    Closed: Re: Shift register with PIC18F4520

    1. remove R4 and R6 they serve no purpose, link the PIC directly to the '164.
    2. read the HC164 data sheet, the input is clocked on the low to high transition, you have it reversed so it will be one...
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    [SOLVED]Closed: Re: Back EMF Diode Configuration

    Circuit A will only work when the diodes are Zener types. Remember a Zener works like a normal diode in forward direction so the clamp voltage is approx Vz +0.6V in both directions, assuming the...
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    Closed: Re: "IR based" relay driving problem

    Nice idea but I doubt it will ever work. LDRs are sensitive to a far wider spectrum of light than you want and are also slow to react.

    A simple but effective solution is to use a second 555...
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    Closed: Re: Need help in LED controlling

    I'm not laughing - honest.

    If kavin_eees will allow an analog solution it is very simple: add a series resistor to the whole feed to all the LEDs. The voltage drop across it will be proportional...
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    Closed: Re: Long OFF_time timer by 555

    I agree a NE555 would struggle to produce timing as long as that but the CMOS version might be able to. The timing would be very imprecise and subject to environmental conditions though. A better...
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    Closed: Re: switch not working with controller

    The LED logic is:
    1. switch open, LED has no voltage across it,
    2. switch closed, 10mA bypasses the LED so there may not be enough current.

    Solution:
    Make R16 at least 1K and preferably around...
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    Closed: Re: Need help in LED controlling

    A further question:
    Do you want to do this using logic or an analog solution. If all the LEDs draw the same current there is a very simple way to detect a third being switched on by looking at the...
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    Closed: Re: Having fun with discrete transistors

    Only showing my age on the outside - I'm still a teenager inside :-D

    Brian.
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    Closed: Re: 230Vac pump drive with a microprocessor

    R44 isn't necessary and R3 may need a slightly lower value but otherwise it should work.
    Note that it may be advisable to add a snubber (33 Ohms and 100nF in series) across the triac MT1 and MT2...
  13. Closed: Re: MCPCB which is double sided and with plated through vias

    So you propose something like the bottom image but made from two of the top image back-to-back with your own plastic insulator.

    Sounds unreasonably complicated and expensive to me and has no...
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    Closed: Re: Voltage control using PWM

    ... I think that was just to detect zero crossing.

    However, using PIC PWM module usually implies a relatively fast PWM rate so unless this is a full inverter (creating a new AC voltage via a DC...
  15. Closed: Re: MCPCB which is double sided and with plated through vias

    Question: are you using double sided MCPCB (assuming that having a core means there is layer each side of it) or are you proposing two single sided PCBs back to back with plastic between them?
    ...
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    Closed: Re: Motion Detector Alarm Timer Modification

    Typically, the pyro detector produces a small signal that is amplified and filtered by one or more op-amp stages then fed to a comparator. There will be some delay mechanism in or after the...
  17. Closed: Re: Common mode noise and earth connections in offline SMPS

    The situation is similar to your crystal set thread where it is aptly described as like a one handed clap. A noise generator has to be between two places for it to have effect, there will inevitably...
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    Closed: Re: PNP transistor not working

    Could do with a clue here - is 'ENABLE' an input to this circuit or an output from it?
    Are you perhaps trying to gate the signal on RC0 so it only gets passed onwards if the supply at J2 is present?...
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    Closed: Re: Having fun with discrete transistors

    I'm pretty sure I've got some NE-2 here in my box of ever ageing junk. Yes, I do remember them in counters and I think there was a commercial frequency counter made by RACAL that used them. I seem...
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    Closed: Re: Voltage control using PWM

    Klaus, CCP1 is one of the capture or PWM output pins depending on configuration. In PWM mode it is an output, in CCP mode it effectively becomes a gate input for counting a clock or a counter input...
  21. Closed: Re: Common mode noise and earth connections in offline SMPS

    I think that would be the preferred way. However, you have to think of the unit as a whole, it may generate noise but how does it get out. If you ignore magnetic radiation which will be very short...
  22. Closed: Re: TO247 FET mounted in "SMD" fashion and pressurized against heatsink with "foam"

    I disagree with both of you! It should be thermally insulating since it is only intended to put pressure against the tab, if it was conductive, and survived the temperature itself, it would distort...
  23. Closed: Re: "Crystal set" radio works only when connected to earth

    Think of the circuit as a 'floating' receiver, it doesn't care where it's signal comes from as long as it's there. What you did was attach an antenna to inject a signal, perhaps not at the optimal...
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    [SOLVED]Closed: Re: PIC12F683 pin high problem

    The same applies to all PICs, the pins can be inputs, outputs or tri-stated. If you are using any as an output and drive it high or low, it will have the ability to source or sink current so driving...
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    [SOLVED]Closed: Re: PIC12F683 pin high problem

    ... but beware that if you tri-state the pin (TRISx register) it is disconnected from the driver circuit inside the PIC so it will no longer pull the base to ground. If you use that method, you...
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