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  1. KrisBlueNZ

    Tildes displayed as dashes (again)

    When I'm typing or editing a post, I can type a tilde and it shows properly. But when I view the post, tildes are displayed as dashes (hyphens). This is confusing and often misleading. I asked about it in the past and someone said that they don't have that problem, so I let it go. But recently...
  2. KrisBlueNZ

    Designing a Time Delayed Relay

    I thought we had chosen a high-efficiency LED (http://www.digikey.com/product-detail/en/LTL2R3KGD-EM/160-1852-ND/2675131) for the power indicator, to operate at 2 mA. That's the amount I allowed in the current budget. In that case, VF is typically 1.8V so R10 would be 1K6. Looks good!
  3. KrisBlueNZ

    RC circuit

    Thanks. I'd already noticed and fixed the 1000x error. And I see what you mean, but I never would have bothered doing that calculation (multiplying 59 µs by 12V and noticing that it matched the time constant).
  4. KrisBlueNZ

    RC circuit

    Here's a schematic and some waveforms from an LTSpice simulation to clarify my previous post. In this diagram, V1 represents gate A, and VA is its output. The "Rser=100" indicates that the gate has an effective resistance of 100Ω in series with its output. This is the ON-resistance of the...
  5. KrisBlueNZ

    RC circuit

    OK... Just to be clear, we're talking about the diagram from post #3 but with the resistor and capacitor swapped over, right? That's an RC integrator. As the capacitor charges up, a point is reached where the voltage at gate B's input is higher than the rising threshold of the Schmitt trigger...
  6. KrisBlueNZ

    Help adding audio out to a TV

    Trace the wires back from the speakers and try to identify the audio output IC. It will probably be in a wide single-in-line package with around 11 pins or so, and mounted onto a heatsink. Post the part number on it. It may be easy enough to figure out where the inputs are.
  7. KrisBlueNZ

    RC circuit

    That's interesting! I didn't know that. No doubt there's a simple explanation. (I'm not asking you to give that explanation though.)
  8. KrisBlueNZ

    Fail-safe shaft rotation sensor

    You can simplify that circuit. All you need is a capacitor that's charged up through a resistor, with a threshold detector connected to it, and a transistor (or similar) that fully discharges the capacitor on every trigger pulse. You can use a 555 as the threshold detector. The important thing...
  9. KrisBlueNZ

    Flasher Help?

    The EL13 seems to be discontinued. There's no information on it on the Tridon web site; there's only the EL13A which is an alternating flasher for hazard indications. Do you have a data sheet for the EL13? Does the EL13 have an earth connection as well as the three you show on your diagram?
  10. KrisBlueNZ

    Help with Yamaha tuner/amp

    Yes, something like that. A sinewave. Try it at low volume and medium volume
  11. KrisBlueNZ

    automatic doorbell

    OK Colin! :-/
  12. KrisBlueNZ

    Help with Yamaha tuner/amp

    Do you have access to an oscilloscope? Or even a computer that can record from a line-level audio input? Capture the waveform across the speaker terminals, ideally with a resistive load connected, and at low and medium volume settings, with a sinewave of say 500 Hz feeding the AUX inputs. You...
  13. KrisBlueNZ

    automatic doorbell

    This project is a doorbell, not a security alarm. It's supposed to work by detecting the ultrasonic waves reflecting of a person as they approach the door, not when they touch the handle.
  14. KrisBlueNZ

    Help with Website Domain/Domain Records

    I've moved your thread to the off-topic members forum. It is not appropriate in the general electronics chat forum. It's probably best to ask on a relevant site. Electronics Point is dedicated to electronics. There's a hint in the name! Alternatively, call or email godaddy.
  15. KrisBlueNZ

    RC circuit

    The capacitor is initially discharged, with no voltage across it. This can only change in response to current flowing into the capacitor. When gate A's output ("A") goes high, the full supply voltage (well, almost) appears across the resistor, because one end is now high, and the other end is...
  16. KrisBlueNZ

    Need help with repair

    Ah. An MJ13005 is not the same as an MJ1005! One little digit makes a lot of difference :-) The MJ13005 looks suitable, but yes, you'll need to add a diode externally across each one. A high-speed diode rated for at least 400V and at least 1A continous. Something like a 1N4937...
  17. KrisBlueNZ

    Help with Yamaha tuner/amp

    Sorry, that unit doesn't have internal speakers. So, try different speakers with it.
  18. KrisBlueNZ

    Help with Yamaha tuner/amp

    The headphone output is taken from the power amp output. If the headphone output is clean, that implies the power amp is OK as well. So check the speakers themselves for damage or deterioration. Also try connecting external speakers instead of the internal ones.
  19. KrisBlueNZ

    automatic doorbell

    How would an RF circuit detect someone approaching a door?
  20. KrisBlueNZ

    Can't find proper fuse!

    I hope you ordered a few of them!
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