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  1. Merlin3189

    UV Sterilization Light

    Can I suggest this link http://www.osram.co.uk/media/resource/hires/334214/technical-guide---starter.pdf which explains the starting process. (With all due respect to Bluejets, his explanation does not sound quite right to me. It's like the first explanation in How Stuff Works, rather than...
  2. Merlin3189

    Audio Generator

    The laptops I had the problem with were both Toshiba with original PSU. I never sorted out exactly what was going on as these were used by other people, so I couldn't spend too much time 'playing' with them. There may have been faults in the amps they were connected to or some effect of the long...
  3. Merlin3189

    Compilation of useful electronics software

    Can I offer a suggestion? Soundcard Scope by Christian Zeitnitz. This is an oscilloscope and a signal generator program which uses the soundcard (obviously!) for I/O. I've found it easy and useful. Limitations; soundcard is AC coupled, so you loose DC info. soundcard is limited to low...
  4. Merlin3189

    How to select proper rating fuse!!

    I'm far from expert in this field and having looked at IEC 60079-11, I think you need some specialist expert advice. An understanding of failure modes and critical parts of your specific circuit/device would be needed. That said, I had a few observations. Fuses operate by melting metal - not...
  5. Merlin3189

    Audio Generator

    Could I just mention Soundcard Scope by Christian Zeitnitz. It sounds just what you need. This contains a two channel audio signal generator as well as the scope and spectrum analyser. Can generate sine, square and sawtooth waves to 20kHz and noise (I think current version also does other...
  6. Merlin3189

    Electrical generation in power stations - how AC Hz and voltage fluctuates

    One little point to add which I can't vouch for, but was recently told to me by an engineer who used to work for National Grid. As well as not letting frequency get too far out of synch, they have to maintain the cumulative number of cycles, so that synchronous clocks maintain long term...
  7. Merlin3189

    Assistance with Transistor Theory

    At the risk of further red herrings, can I ask about something which has long puzzled me about these holes. Ratch said, "A lot of folks seem to think that a hole is simply a missing electron in the conduction band. The hole in the valance band is every bit as real as a electron. It has its...
  8. Merlin3189

    Assistance with Transistor Theory

    Wow! I just pop off for a turkey, a few bottles of wine and a mince pie, then I come back to this! Well there have been so many points made that I can't air my ignorance on all of them (but I expect there'll be plenty of chance later!), so can I just ask a question? Sometimes I think that there...
  9. Merlin3189

    Anyone able to help me out for my invention?

    Try a switch operated by the solenoid. When the solenoid has moved its armature to the full extent, it operates a switch to break the current. That way you do not have to know the operating time of the solenoid (which I expect would vary with conditions such as temperature and pressure) - it is...
  10. Merlin3189

    Any electronics experts from South Africa?

    Pin 3 output should be low, but there is a transistor beween pin 3 and ground, so there will be a small saturation voltage on it. That will only be about 0.1V unless you pass current into it. Also you should connect trigger, threshold and reset to Vcc to ensure that the output is low. I think...
  11. Merlin3189

    Assistance with Transistor Theory

    I am happy to agree that the base-emitter junction will behave like any other diode. I did not know of the Gummel-Poon model and have only a vague recollection of the Ebers-Moll equation. No doubt if I understood these, I could do some complicated calculations and might gain some useful...
  12. Merlin3189

    Assistance with Transistor Theory

    When I saw LvW's intro, I felt a bit sympathetic. People do seem a bit intolerant of dissident views. But having read the rest, my sympathy waned! Laywah can decide what to think, but I'd like to offer a PoV. "you must know that the BJT is a voltage controlled device. " I disagree: A BJT is a...
  13. Merlin3189

    Crytal Oscillator

    Looking at Wiringelectronicscircuits you seem to have picked the odd one out. There are several other circuits where the output is taken directly from the emitter, rather than from a low tap. So either try that or use a higher tap ratio. I see the reviews for that circuit say 50% good, 50%...
  14. Merlin3189

    Crytal Oscillator

    Well I'm no great expert, but I think you could do that. Yes you do want a clean(ish) sinewave output (if it's modulated it's not that clean of course), but transmitters often use very un-sine wave generators and, as you say, use an LC 'tank' circuit to select the frequency required. Then there...
  15. Merlin3189

    Crytal Oscillator

    Just having a quick look at your circuit, I'm a bit puzzled as to why you expect much more output? With a 9V supply, can the oscillator stage have more than about 4.5V AC on the emitter? Then you tap off the output from C2 : C3 junction, which looks like it would be an AC potential divider...
  16. Merlin3189

    3 watt LED mounting..

    You're right about there being limited info on epoxies. Presumably they think it's of interest only to industrial scale buyers. But if it's of any help, ALH make NP2001 water clear fast cure resin with specimen thermal conductivity of 0.2 W / K m (cf their high thermal conductivity resin...
  17. Merlin3189

    Transformer? Choke? What?

    Just out of casual interest I wonder what this is? I have it simply because it has a lot of copper in, but before I remove that, I wondered what use it might have? Each half is one continuous winding with taps fairly evenly spaced. The two windings are by rough measurement the same. The two...
  18. Merlin3189

    How do energy plants safely measure power

    Well, not being psychic I may well be wrong. Yes OP was possibly not serious, but did ask a question. As I said, your answer did seem to answer it up to a point, Hevans answer was interesting and informative about why someone might want to measure the output, and how they would process that...
  19. Merlin3189

    How do energy plants safely measure power

    Well said Bluejets - an increment in information. Without wishing to offend Hevans, changing, "how do you measure power" into "... using a data acquisition system that monitors line voltage and line current " does not add much for most people, who probably understand P=VI. The question from...
  20. Merlin3189

    The art of electronics

    I don't have it any more, but had one years ago and thought it the best general electronics reference book around. I know many others at the time thought so too. I lost mine when I lent it and it did not return: seems to be the fate of many of my best books! I have sometimes been tempted to...
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