Type: Posts; User: betwixt

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  1. Replies

    Closed: Re: TCM3105 modem modes please explain

    From the data sheet:
    which implies it has an analog frequency discriminator. That means it cannot distinguish signals between two simultaneous signals in the same frequency range so either the...
  2. Closed: Re: Dimming the MP2489 right down to zero (Buck LED driver)

    If I understand the data sheet, the input is always analog but the voltage range is limited to the internal Vref. It gives you the option of controlling output current by dropping the enable voltage...
  3. Closed: Re: Multiplexing problem in my 8051 clock project.

    I think that should win a prize for the most convoluted and un-commented code ever written to do a simple task.
    When writing a program like that you should first look at the individual tasks it has...
  4. Replies

    Closed: Re: analog pressure gauge to 4 to 20mA

    We have no idea what size the pressure gauge is but if we assume it is a standard rotary type with a moving pointer, my approach would be to remove the pointer and replace it with a transparent...
  5. Replies

    Closed: Re: transistor selection help question

    The data sheet for the 2N4401 says it should typically drop 0.75V between collector and emitter pins when passing 500mA but you need to give it 50mA base current for it to achieve that.
    However, the...
  6. Closed: Re: Operating four Tx-Rx pairs in close proximity

    I use sequential addressable transmitters with active time of only a few mS, faster than a HT12 can send a single code. Given their close proximities, especially the transmitters it would make more...
  7. [SOLVED]Closed: Re: PIC16F877A controlled 74HC595 by serial command

    I cannot use Proteus but looking at the code it seems you overflow the receive buffer after a few characters have arrived fro the USART.
    You use
    char buf[]={0x00,0x00,0x00,0x00}; ......

  8. Closed: Re: How to Identify CentOS and Ubuntu Paritions?

    Almost certainly yes.
    However, if you use the "lsblk -fs" instead it will also tell you which type of filing system is on the partitions. The letters "/dev/SDx" tell you which physical or OS device...
  9. Closed: Re: How to Identify CentOS and Ubuntu Paritions?

    Windows probably won't help you but if you open a terminal window in Linux try one of these:
    lsblk -a -fs
    sudo fdisk -l (lower case 'L')

    You can also try graphically with 'Disks' or 'gparted' if...
  10. Replies

    Closed: Re: Change colors of liquid crystal display

    It isn't impossible to what you want but it isn't as easy as you imagine.
    Light falling on the face of the LCD (such as Sunlight) passes through TWO polarizing layers but light from the back only...
  11. Replies

    Closed: Re: What Signal is this?

    A rather vague question. If you fed the top waveform into a low pass filter AND it had the right cut-off characteristics AND it had an appropriate load, then yes you could get the lower waveform...
  12. Replies

    Closed: Re: TRIAC wont conduct, some advice needed

    If anything I would expect it conduct most of the time. R2/C1 are a phase shift network to delay the trigger voltage reaching threshold and hence reduce the time current flows but it should conduct...
  13. Closed: Re: Lamp Test Circuit with some other indications.

    I agree FvM but I couldn't think of any other path that would allow only a small current to flow. The series diodes, assuming they are normal Si types should block reverse current anyway but the two...
  14. Closed: Re: Lamp Test Circuit with some other indications.

    Looks like a device for killing LEDs to me. I assume they all have series resistors.
    Maybe you are seeing leakage through reverse-biased LEDs because of the relatively high voltage exceeding their...
  15. Replies

    Closed: Re: Well regulated mains to large cities

    Sorry about the typo - it is indeed 4,320,000 cycles per day.

    I (in the UK) have never come across a regulator device in the mains supply, the local transformer serves about 100 properties but it...
  16. Replies

    Closed: Re: Well regulated mains to large cities

    I think it is on a much bigger scale.
    In my area they switch whole power stations on and off to keep the mains steady. We have a 50MW hydro electric generator about 30Km away and another 498MW...
  17. Replies

    Closed: Re: Suppliing fans with a power adapter.

    Fans draw ("take") as much current as they need. In your case they draw 0.39A each so the total is 1.56A and the 2A adapter should work fine.
    The 2A figure for the adapter is the limit it can...
  18. Replies

    Closed: Re: AutokeyReset function

    I have no idea what your schematic and setup is but that isn't what you originally asked for and you didn't do as I suggested.
    Firstly, please comment your code and indent the functions, it makes it...
  19. Replies

    Closed: Re: Astable Multivibrator not switching

    Silly values.

    R5 and R6 serve no purpose but to reduce the available current to the transistor bases. Remove them from in series with the bases and instead place them as bias resistors between...
  20. Replies

    Closed: Re: LED headlight pcb reverse engineering

    The schematic doesn't make sense so there must be errors in it I'm afraid.

    It looks to be a low power headlight, maybe 3W at most so it can't be very bright. Even if both high and low beams are on...
  21. Closed: Re: Recommendation needed for gain of antenna for a 2.4 GHz wifi extender

    First establish whether the rain problem is due to atmospheric conditions or the change in wall material absorbing the signal. If it is the latter (it probably is) the only real solution is to mount...
  22. Closed: Re: Digital Storage Oscilloscope - newbie questions

    I think what you are seeing is not one trace but several similar traces appearing to overlap. There is only one trace at a time but it is repeating rapidly and giving the impression of a more...
  23. Replies

    Closed: Re: Forward voltage of blue 3 mm led

    If you directly apply a voltage below Vf, the LED will not light up.
    If you directly apply a voltage above Vf, the LED will burn out.
    You MUST use a resistor or current limiting circuit to prevent...
  24. Replies

    Closed: Re: How to make a lumen meter?

    Firstly, you cannot calculate the light output purely on the DC input power to an LED. The missing factor is its efficiency which varies greatly across products and design purpose.

    There are other...
  25. Replies

    Closed: Re: Antenna and microwave business website

    Maybe in your country but more generally there is a huge demand for information relating to radio communications, including how to get signals from one place to another. If you encroach on military...
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