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  1. duke37

    Negative Voltage on Breadboard with no negative voltage input

    It depends on the current you want. A two transistor or 555 multivibrator can produce an AC source which can be capacitively coupled to a rectifier. There are chips made for this job.
  2. duke37

    Step-down transformer suddenly stopped working - but why?

    Transformer windings can go open circuit for various reasons. The transformer may have a thermal fuse in the primary to stop current if the transformer gets too hot. This not the case if you have a connection through the primary. Corrosion can affect either winding. Old transformers suffer...
  3. duke37

    Unstable latching circuit`

    A resistor to the gate will limit the current and hence the voltage. It will never get over a volt or so unless you are abusing it. Some conductance between strips is not likely to be due to solder, that would either connect or not. The most likely cause is contamination with flux. Try...
  4. duke37

    Photocathode - Night Vision

    One part you have left out is the very high vacuum. You could go to outer space to collect some.
  5. duke37

    dc 12v 2amp

    Be careful. The device will only take up to 2A, the car can supply much more than this so it is well up to the job. The car supply is likely to be dirty with considerable voltage variations. Your device must be able to cope with these. You must connect the supply the right way round or it...
  6. duke37

    Diode lab experiment

    The diode has a logarithmic response to voltage. If I remember rightly, the current goes down by a factor of 10 for every 60mV drop. Thus if you can measure very, very low currents, you can go below 0.5V. Diode data sheets may give the answer you require.
  7. duke37

    Unstable latching circuit`

    As you say, the lower the value of the resistor, the less sensitive it will be. If you connect the gate to the cathode it should not work at all. You have chosen a thyristor with a very sensitive gate. You say you have checked the stripboard but have you measured the resistance from one strip...
  8. duke37

    LM317T and how it works

    This should give slightly under 5V out. The temperature will depend on the load current. A buck regulator may give more problems if is is noisy.
  9. duke37

    Unstable latching circuit`

    i did not see any data in #21 I show a sketch of how the SCR should be connected. I also show how a relay can be latched without electronics.
  10. duke37

    Is solder really dangerous?

    It is resonable to take precautions even if you know someone who manages to survive. I think the flux fumes are nasty. Electronic solder is 60% tin/40% lead. Plumbers solder is 60% lead/40% tin, plenty of room for confusion here. Plumbers used to have lead poisoning because they would wipe...
  11. duke37

    Unstable latching circuit`

    Raising the resistance will make the gate more sensitive. You should be OK where you are. I could not find what the SCR is that you are using. The C106 has a sensitive gate.
  12. duke37

    LM317T and how it works

    You can look up the data for the LM317T. I would expect that the output would not vary more than a mV or so with the input range you have. You will get a little variation in voltage if the current varies, perhaps another mV. So, is the answer to your question Yes or No? Make sure that you...
  13. duke37

    Unstable latching circuit`

    As Fish4Fun says it is easy to trigger a thyristor. Some are more sensitive than others. It is normally recommended to put a low value resistor from gate to ground. I have seen values of 100 to 1000 used. This means that any slight internal leakage does not trigger it on.
  14. duke37

    Is solder really dangerous?

    Make sure you wash your hands thoroughly after handling solder. I keep my reel of solder in a plastic bag with a little hole with the solder coming through. Thus I do not handle the reel. Dats wot i finc.
  15. duke37

    New to the forums and looking for some advice

    There is a thread on this forum suggesting good books. You can also get a lot of information from Wikipedia.
  16. duke37

    capacitor

    If it is connected directly across the supply when at zero voltage without resistance, then it will be fully charged in a quarter of a cycle.
  17. duke37

    revered polarity LED

    I could not open the link but it looks as if it refers to a Schottky diode, a posh one like this is not necessary. In fact it is not as good as a normal diode in this application. I would suggest at Maplin (pricey) 1N914 or 1N4937. Other places can supply 1N4148 or 1N4007 at lower cost but...
  18. duke37

    revered polarity LED

    An LED passes curent in the forward direction and will tend to stop current in the reverse direction, however, 7.4V is perhaps a bit much for it. You could put a diode across the LED to pass current in the reverse direction and so limit the voltage to abou 0.6V. Alternatively put a diode in...
  19. duke37

    Book Reviews

    Electronic Filter Design by Arthur B. Williams 1981 I think there is a later edition. Designs of low pass, band pass and high pass filters, passive and active. Various filter types, Butterworth, Chebyshev, Bessel, Linear Phase,Transitional Gaussian usually up to seven pole.
  20. duke37

    Book Reviews

    The Technique of Radio Design by E.E.Zeplar 1943 A classical book for those who wish to know how things were before semiconductors.
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