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  1. Merlin3189

    Wiring a Transformer

    See http://www.trcelectronics.com/Cosel/pdf/Manuals/vaf_manual.pdf FG = frame ground It appears to want to be attached to the mains earth, via the metal housing or directly if there is no earthed housing. Don.
  2. Merlin3189

    Making a Transformer

    Primary EMF Yes, that's what I thought when I first read the question: I always take the PD across the winding as the input emf. But on reflection, don't we model the primary as a resistance in series with an inductance? So connect it to 230V AC and, say 1V is dropped across the R and the...
  3. Merlin3189

    circuit wiring help please

    Motors My diagram seems not to have uploaded correctly, I'll try again
  4. Merlin3189

    circuit wiring help please

    To the Superuser Bennett I've got a suggestion for this problem. As it is a project, I'm not sure how much too say. So these are my ideas: pass on as much as you think appropriate, if anything. I make no comment on the mechanical arrangement - his diagram doesn't really tell me enough of...
  5. Merlin3189

    Design of astable multivibrator

    Well I get that roughly to 250Hz, which is in fairness about 10^3 less than I said you might get. So as Steve says, reduce your capacitor to nF rather than uF and you should get a much higher frequency. (I'd try around 47nF aiming for 10kHz for starters, because I'm not so confident it will go...
  6. Merlin3189

    Design of astable multivibrator

    If SR=13 V/microsecond, then using T=2 x Vss / SR at Vss=15V gives T= 2 x 15 / 13 microsecond = approx 2 microsecond So SR limit to frequency is about 500 kHz When you say you get a practical max which differs by 10^3 from that, are you saying that you get a max frequency of about 500 Hz ...
  7. Merlin3189

    Capacitor marked 4n7M, 4kV-E; Is that 4 or 4.7nF?

    There's a useful little summary here: http://www.electronics-tutorials.ws/capacitor/cap_5.html What would worry me about these, is the 4kV. If that's a voltage rating, it's pretty important, as you don't bump into capacitors that can take 4kV everyday. You'll probably know from the application...
  8. Merlin3189

    RF Mixer

    Apologies for odd layout in previous post. I pasted from Notepad into Quick Reply and it got a bit scrambled.
  9. Merlin3189

    RF Mixer

    I'm no expert, but perhaps I can give you a start. I think the confusion is between the bandwidth (BW) of the signal and the BW of the filters. When a radio signal is created, a nominal carrier frequency is modulated with an information signal and new frequencies called sidebands are created...
  10. Merlin3189

    Design of astable multivibrator

    Real components are not ideal - and good simulation programs try to allow for this. The T/2 >> Vss / SR gives a limit which the oscillator could not exceed, but it does not say that you can get anywhere near it. The formulae for the RC frequency are based on the assumption that the op-amp...
  11. Merlin3189

    Help wiring multiple flashlight LEDs

    Driving LED arrays 1 - The lamp I have has 24 LEDs all in parallel, with no resistors at all and is driven by 4AA cells. The current distribution is inevitably very uneven and some LEDs are much brighter than others. As others have said, a bad situation relying on the cells' internal...
  12. Merlin3189

    Design of astable multivibrator

    Astable The formula for upper limit to max frequency can be seen from the graph of the output when it is slew rate limited. You can take that (ideally) as a linear sawtooth with slope equal to the slew rate (the maximum rate at which the output can change.) The Voltage swing is (again...
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