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  1. dorke

    Clean square waves using a 555 timer?

    Yes ,that would do fine. Decouple the IC with a tantalum(doesn't have to be 10uF,2.2uF and higher should be fine) and a 0.1uF ceramic and use shortest leads possible. If you can ,please do the 3 tests in #61 ,on the breadboard. The results may be interesting.
  2. dorke

    2W Voltage amplifier help

    Welcome to EP. 1. I can't see any 2W in your design or requirements. 2. 50ohm signals are normally AC and not DC,you need to clear that point. Find out what is the signal you need to amplify and it's frequency range as well.
  3. dorke

    Clean square waves using a 555 timer?

    1. We know for a fact that the 555 isn't properly decoupled here( post #49 item3). 2. Yes, the 555 "Totem-pole" is known to bridge the vcc line to GND and produce a large switching current spike. This point is actually one of the improvements made in the CMOS versions (lower PS switching...
  4. dorke

    Clean square waves using a 555 timer?

    O.K Let's take this to a higher level of understanding: going into the "guts" of the 555 output stage and it's output characteristics. I'm going to do it on the intuitive level using equations as little as possible. First let us start with an NPN transistor in saturation. In saturation both...
  5. dorke

    Clean square waves using a 555 timer?

    Could you please post the results of the 3 simple test in #61
  6. dorke

    Clean square waves using a 555 timer?

    We should use the circuit with the diode not the "non-working " very problematic circuit. As I said it isn't a good idea to use the output of the 555 for "auto-timing" purposes,like it is done here. About your suggestion , we could ,up to a point. As they say "there are many ways to skin a...
  7. dorke

    Someone please help clicking relay

    No need to bet. Put your finger on the black plastic casing (without touching any thing else) , you will feel the clicking one very clearly.
  8. dorke

    Clean square waves using a 555 timer?

    Chris, True the 1K limits the current as you say. But the slopping behavior is entirely due to the series cap. A voltage drop of 1V(and more )from VCC is normal for the 555,even at relatively low output current of a few mA. The reason being the output of the 555 isn't rail-to-rail (it is so...
  9. dorke

    Very compact voltage dropdown

    You can try the 6v camera grade lithium battery 28L 2CR11108 L544 . It is small and will last longer the the 9V one.
  10. dorke

    Can't identify if transistor is PNP or NPN?

    Excellent analogy,could you believe that's the first time I hear that. Learning something each day,I like it:)
  11. dorke

    search for a Varistor replacement compatibility

    My pleasure, I would clean that board with a small dry paint-brush an a vacuum-cleaner.
  12. dorke

    Zeroing out a LM317 reference voltage with a zener - PSU build

    Not to that extreme... Yes you can learn a lot about regulators ....from there smoke-sines as well;) But seriously , I think building a simple single-output low-current regulated P.S with current-limit is essential for learning. Using only the classic series pass transistor with a transistor...
  13. dorke

    Detecting alternating current in my PSU heat sink (leak?)

    About the ESR issue of caps. That applies only to the caps. working in the fast switching parts of the SMPS(flyback). On this specific board there are many caps. which need not necessarily be low ESR ,as they are filter caps on the linear regulators.
  14. dorke

    Zeroing out a LM317 reference voltage with a zener - PSU build

    I thought it goes without saying, the PC P.S only for powering digital boards-and they are great for that. For learning , the way to go is building the linear P.S using only transistors,diodes and op. amps , no 3 pins regulator ICs at all.;)
  15. dorke

    Someone please help clicking relay

    We need to find the service manual or the schematics. You should tell us the part number identifier of the relay on the board.
  16. dorke

    Someone please help clicking relay

    LOL, Or he thinks it's is 2nd life as a metronome.
  17. dorke

    How does this work?

    The 555 is wired at it's most basic way as a mono-stable. Pin 5 lacks the decoupling capacitor. When there is light("constant " )on the LDR the output will be "high" , thus LED will light-up but the buzzer will be silent. Is this a bug or a feature? The op. should tell us...;)
  18. dorke

    Can't identify if transistor is PNP or NPN?

    What at terrible circuit diagram.o_O No need to guess,the Emitter-arrows point inwards ==> they are both PNPs. Here is a site that will clear things for you, and another one here.
  19. dorke

    Someone please help clicking relay

    Start by letting us know the model number. What makes a relay click? First thing is to identify it and the function it performs in the circuit.
  20. dorke

    Coil problems...

    Hop, your ebay link goes to Antennas...;)
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