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  1. Replies
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    Closed: Re: Latched Relay Car Immobilzer

    That is correct.
    With no power applied, there is no path to power the relay coil. When the switch is pressed, power reaches the coil and the contacts close. From then on, until the power is removed,...
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    Closed: Re: how to change pir sensor coverage angle?

    I wouldn't 'tweak' a commercial product, I would start from scratch.

    I assume this is just a one-off project and not for mass marketing so I would suggest you get hold of an old scrapped TV or VCR...
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    Closed: Re: Latched Relay Car Immobilzer

    You almost have it right. the relay contacts on the left go across the momentary switch instead of chassis. Basically, it makes it think the momentary switch is being held closed. Wired as shown the...
  4. Closed: Re: Will the TVS diode protect the DC line from AC power?

    The TVS will protect against excessive voltage provided the current is limited to a suitably small amount but it will not protect against the polarity reversing. For example, if the TVS clamps to...
  5. Closed: Re: Protecting the inputs of HV7802 current monitor from damage due to inrush current

    I think that should be 100uV not uA Klaus ..... but we know what you mean :-D

    Brian.
  6. Closed: Re: Mains leaking currents causing problems in my house

    Beware, most 'plug testers' work by looking at the difference between the three pins, live, neutral and earth. As you only have two pins it may not work.

    There is an alternative that would make...
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    Closed: Re: how to change pir sensor coverage angle?

    That is exactly the thing but it only has a range of 10m (about 30 feet) so you would need more than one to give the 50' length you need.
    With a little effort you could make one with the same or...
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    Closed: Re: Elementary battery question

    It is a standard 18650 Lithium Ion battery. There are many chargers for it if you search with that number. There are three wires, one will be a common connection to the battery negative and a...
  9. Closed: Re: FSK 1200baud discrete "modulators". What do you think?

    The problem is the frequencies are low compared to the data rate. A change to logic high or low is likely to result in partial cycles of the tone and hence all kinds of spurious other frequencies....
  10. Closed: Re: Input stage to 24W buckboost LED driver is high in component count.

    At such low current and with a surge limiter after it, do you really need a very low Rds FET? The difference between all that circuit and a simple silicon diode will be ~0.5V at most. I appreciate...
  11. Closed: Re: Input stage to 24W buckboost LED driver is high in component count.

    Thought:
    As the first stage is only to block reverse polarity, can't you replace it with a diode?
    If the second stage is only powering the comparator and the 5V is decided only by D51 and the Vbe...
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    Closed: Re: STM32 16bit wav player using Dac

    I'm not sure exactly what that does but I suspect the '=' shouldn't be there.
    I'm also not sure you should convert to signed at all, does the DAC accept signed numbers?

    Brian.
  13. Closed: Re: Simple dipole compared to a folded dipole in a 2.4 GHz Wifi Yagi Antenna

    I would use a much narrower boom, the capacitive effects of so much wood covering half the elements would seriously de-tune it. I have used brass rod as the boom before with good results. 6mm dia...
  14. Closed: Re: Lumens/Watt in LEDs when forward current is very low.?

    Intuitively I would say it continues down to zero almost linearly. I would guess the graph doesn't go lower simply because it is outside the scope of normal usage, just like car fuel usage is...
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    Closed: Re: Limit Current Maintain Voltage PSU output

    You are asking for contradictory requirements but what I think you want is a constant voltage power supply with an indication when the current has exceeded 150mA.
    You will have to start with a...
  16. Closed: Re: Mains leaking currents causing problems in my house

    It's a long story but basically, the cable carries on beyond my house to a three-phase motor on a waste treatment plant nearby. The cables used to be overhead but trees fell across the wires and...
  17. Closed: Re: Mains leaking currents causing problems in my house

    Neutral and Earth are usually bonded together but not at the socket, it is done back at the distribution transformer where both have a real 'planet Earth' ground. If you bond them at the socket and...
  18. Closed: Re: [moved] Why Zener getting heat at no load in Capacitor power supply arrangement..

    Short answer, you can't. The Zener will always dissipate heat, the best you can do is as Schmitt Trigger states, its to remove the heat as efficiently as possible.

    The whole idea of that kind of...
  19. Closed: Re: [moved] Why Zener getting heat at no load in Capacitor power supply arrangement..

    I agree, the calculations look correct and it works as expected. You will find that if the LED and relays are operated, the Zener goes cold, that is how a shunt regulator is supposed to work.
    Note...
  20. Closed: Re: Mains leaking currents causing problems in my house

    Here the standard for 32A breakers is they feed a ring (so two paths to each socket) of 2.5mm copper. Looking at the bottom photo in post #6, in addition to the existing wires there would be a...
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    Closed: Re: how to change pir sensor coverage angle?

    By interrupter we mean that rather than look for IR (heat) radiating from an object to trigger the alarm, instead a beam of light is generated and targeted at a sensor along the path being tested. If...
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    Closed: Re: Question about RF power meter

    000SHREDDER000, we are not being obstructive or critical but you original question was very misleading. When you said you wanted a range wider than 60Hz people assume you are looking for something...
  23. Closed: Re: High frequency oscillator circuit with IC TL494 as control circuit and IRFZ46N MO

    Please post images and files here mkanas, some, probably all of us can't open your google drive documents without your password.

    Brian.
  24. Closed: Re: Mains leaking currents causing problems in my house

    I'm with FvM on this, without a protective Earth on the PC chassis it would adopt roughly half AC voltage simply because the input mains filter will have approximately the same value capacitors...
  25. Closed: Re: [moved] Why Zener getting heat at no load in Capacitor power supply arrangement..

    Your calculation and concept of power are wrong.

    The Zener is in shunt configuration - it 'soaks up' the excess current that isn't flowing into the load and in doing so it dissipates heat. The...
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