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  1. Closed: Re: how to select capacitor for ruhmkorff coil?

    I would argue the opposite. It helps to preserve the contacts although there is some additional loss as the capacitor is shorted out and discharges into the contacts. The coil is essentially a high...
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    Closed: Re: Ferrite vs wire antenna for MW

    The wire will win easily but if this is an energy harvesting experiment you should be aware that a few microwatts of power is all you are likely to get.

    Brian.
  3. Closed: Re: how to select capacitor for ruhmkorff coil?

    It isn't necessary to use one at all but I would suggest something in the region of 0.22uF if you insist on using one.

    These are not user friendly or efficient devices, you can get better results...
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    Closed: Re: Ferrite vs wire antenna for MW

    I used to listen to New York and Boston stations here in the UK years ago, before the noise pollution became to great. That was on a long wire antenna.

    An outdoor antenna will undoubtedly work...
  5. Closed: Re: computer parallel port external relay control

    Frank, it would be helpful to know how you control the parallel port at the moment. Obviously some software is involved and it probably writes directly to the ports hardware address. You would have...
  6. Closed: Re: Resistance of component bag made of "reddish" ESD plastic?

    All of this goes around in circles. Static is a fact of life, it isn't the voltage that causes harm, it is the voltage difference when charged items touch each other.
    If voltage alone did harm,...
  7. Closed: Re: computer parallel port external relay control

    The real problem is finding a parallel port on a PC these days. When one does physically exist you have to jump through hoops to bypass the vitualization so you can talk to real hardware.

    A more...
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    Closed: Re: Cw decoder by ik3oil

    The photographs show a 16x1 LCD.
    The code is for a 16x2 LCD.

    In the "inilcd" routine, the line that sets the display geometry is You can edit the binary for other display sizes. The length of...
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    [AVR]Closed: Re: Temprature sensors. LM35 vs MCP9700

    TA[1] = TA[1] + (analogRead(A1)- 500)*vREF/1024*100;
    Are you sure that subtracting 500 is the correct value. I'm not familiar with the Arduino Nano but the final measured voltage should have around...
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    [AVR]Closed: Re: Temprature sensors. LM35 vs MCP9700

    .... and did you compensate for the zero offset on the MCP9700? The devices are not directly interchangeable.

    Brian.
  11. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    FvM - not according to the schematic in post #42. With the pots at minimum resistance it places 240V AC across the 100uF capacitor.

    Not quite true, if you take your half cycles and trigger at 90...
  12. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Look at what happens if you set both potentiometers to minimum resistance - you effectively connect the capacitor across the incoming AC. That means the capacitor has to be rated for at least 250V...
  13. Closed: Re: PIC16F877 interface with ds1307 ...RTC running 10 sec slow

    Timekeeping is internal to the DS1307 so the interface code is unlikely to be the problem. Taking 70 seconds to complete one minute implies the RTC crystal is running at 28.086KHz instead of...
  14. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    The schematic shows a normal diode but the text calls it a 'trigger diode'. In a real circuit a diac would be used. A diac isn't like a normal diode, it doesn't conduct at all in either direction...
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    Closed: Re: UC3845 ETD29 transformer PWM signal

    The problem with your simple flyback converter is we simply cannot see it. Please post a schematic and tell us where exactly the waveform is being checked.

    Brian.
  16. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    'Ground' in a simulation means the reference point that everything is measured from, it doesn't have to be a connection to the Earth beneath your feet.

    There is no issue with placing the load in...
  17. Closed: Re: How to mitigate large area ground current loops in large arrays of paralleled SMP

    "circulating currents" doesn't really tell you anything, all currents 'circulate' to be able to do anything useful. If they mean ground loops, that is something you can design out by ensuring the...
  18. Closed: Re: How to mitigate large area ground current loops in large arrays of paralleled SMP

    "Large" is a relative term. Compared to the total power I would think noise relatively unimportant and the relatively sluggish response of the power supplies would work like an LPF.

    I would think,...
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    Closed: Re: ST7036i and mikroc STUCK

    The result is a boolean 0 or 1, it can't be anything else so you can re-write the code like this:

    void ack(){
    if (ACKSTAT_bit) UART1_Write_Text("No Ack");
    else UART1_Write_Text("Ack");
    }

    but...
  20. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    Think of the SCR as being a normal diode after being triggered. Substitute a real diode in the schematic and you will see what I mean. In conducting mode the real forward voltage depends a little on...
  21. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    That is correct, and it is what the oscilloscope shows. The negative half cycles are when the SCR is NOT conducting, remember it only conducts in one direction, the tiny rise above zero on the...
  22. Closed: Re: Non isolated SMPS does not need Y capacitors?

    What I'm not grasping is WHY the chassis can't be a circuit conductor. Making it so would greatly simplify the EMC problem as there would be no voltage difference across the critical points.
    ...
  23. Closed: Re: Where to get schematics about SCRs full-wave triggering circuits ?

    To reiterate: the trigger voltage is applied between the cathode and gate , that means if you lift the cathode voltage, the gate voltage has to be that much higher. Allowing the cathode to change is...
  24. Closed: Re: Non isolated SMPS does not need Y capacitors?

    If I understand the problem correctly:

    1. you have a 'chassis' (presumably the outer casing of the base unit) that should have no signals on it referenced to ground.
    2. You have two unshielded...
  25. Closed: Re: Non isolated SMPS does not need Y capacitors?

    Everything is relative.....

    If your chassis is ground and your reference is ground, there is no antenna effect.

    Brian.
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