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  1. KrisBlueNZ

    Help designing circuit for box alert light

    Yeah, I'd go for the latter. Feed the LDR through a Schmitt to a C-R pulse generator (differentiator) then a diode, to set the latch.
  2. KrisBlueNZ

    Possible Project??

    What are the nominal resistances of the two solenoid coils? Are they fully isolated from each other? Would it make sense for the hand-held tester to simply check that the resistances are within range, and if they aren't, you would disconnect the tester and use a multimeter to see what the...
  3. KrisBlueNZ

    A/B USB switch box noise

    Right. It's probably best to keep the grounds from the two computers isolated from each other. Run everything through the switch, so the unused computer is completely disconnected from the path from the active computer to the audio box.
  4. KrisBlueNZ

    Help designing circuit for box alert light

    Steve, how will you be able to reset the latch if the box is open and the LDR is illuminated? The reset button is inside the box, remember!
  5. KrisBlueNZ

    Charging Capacitor Bank

    Four 110 µF 320V capacitors in series are equivalent to a 27.5 µF 1280V capacitor. You would need a winding with very large number of turns to generate this much voltage from the flyback energy from a 1.5V battery, and it would take a very long time to charge. You would need a high-voltage...
  6. KrisBlueNZ

    pic programming help - controlling GSM to send message from PIC16F873A

    Can you answer my other questions?
  7. KrisBlueNZ

    dc to dc boost converter

    Hiya Dave :-) Happy New Year to you too mate :-) Yeah LOL. Good on him for posting pics though.
  8. KrisBlueNZ

    dc to dc boost converter

    The circuit board shown in the second and third photos is a buck regulator using a National Semiconductor switching device, not a boost regulator using the XLSEMI device shown in the first diagram.
  9. KrisBlueNZ

    VGA to Sync on Green

    I don't know why it worked either. But as long as it does... great!
  10. KrisBlueNZ

    VGA to Sync on Green

    Yes, your diagram in post #28 is what I suggested. I was hoping it would work... Here is an explanation of Tomi Engdahl's circuit from post #10. Horizontal and vertical sync signals from the VGA card are processed separately in the two gates connected to R1/C1 and R2/C2. The resistor and...
  11. KrisBlueNZ

    Happy new year everybody.

    Happy New Year to all my Electronics Point friends :-)
  12. KrisBlueNZ

    Wireless Doorbell Mod Help!

    Yes, you should be able to use two cores from the Cat 5 cable to connect the pushbutton to the transmitter. I thought you would be mounting the transmitter right beside the button...? Happy New Year to you too :-)
  13. KrisBlueNZ

    Wireless Doorbell Mod Help!

    OK. I think your simplest option would be to drill holes and mount an LED inside the button. The LED can be powered via the Cat 5 cable. This means the pushbutton can be connected directly to the transmitter board, in parallel with the existing pushbutton, with no special circuitry needed. With...
  14. KrisBlueNZ

    Wireless Doorbell Mod Help!

    Detecting a button press when the indicator is connected across the button can be done by feeding a current into the button and monitoring the voltage across it. When the button is open circuit, the current will flow through the lamp or LED, and will cause a voltage to appear across it. When...
  15. KrisBlueNZ

    Isolated sense of AC mains (240V) voltage and phase

    Are the energy meter chipsets also too expensive? Or not suitable? There are several around, from Analog Devices, Maxim and others. If you haven't checked them out, Google energy meter chipset.
  16. KrisBlueNZ

    Isolated sense of AC mains (240V) voltage and phase

    I was considering suggesting the IL300 but I'm not sure how accurate they are over time. I guess if the degradation is only in the LED, not the phototransistors, it should remain accurate for a long time. Adam, re AC voltages in LTSpice, what you said is the same as what I said. The value you...
  17. KrisBlueNZ

    Panasonic NV-HD650A sound

    It's a VCR.
  18. KrisBlueNZ

    Isolated sense of AC mains (240V) voltage and phase

    Yes, I agree with Harald's suggestion. Convert the voltage to digital on the mains side and use an SPI connection through some fast optocouplers to transfer the data serially across the isolation barrier. Another option is to do your signal processing on the mains side, and pass the final...
  19. KrisBlueNZ

    How do I hook this up to my computer?

    What kind of output connectors does it have? Are they RCA Phono plugs? Do they plug into an amplifier? If so, as Steve says, you'll need a sound card to convert the analogue voltage signals from the turntable into digital so your computer can process them. A manual would be very helpful.
  20. KrisBlueNZ

    Isolated sense of AC mains (240V) voltage and phase

    Hi Roger and welcome to Electronics Point :-) Check your AC mains voltage. In LTSpice, a sinewave AC signal with an "amplitude" of 240V is NOT 240V RMS - it's 240V peak! Unexpected quirk of LTSpice. Check by looking at the voltage waveform. You'll see it's 240V peak. The trouble with...
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