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  1. KrisBlueNZ

    Laser Driver Troubleshooting?

    Hi Noura and welcome to the Electronics Point forums :-) The 1.25V that kpatz is referring to in post #2 relates to the resistor between the OUT and ADJ pins of the LM317. The LM317 has a 1.25V internal reference voltage, and that is the voltage it will try to maintain between OUT and ADJ. So...
  2. KrisBlueNZ

    Transformer Voltage Amplifier

    Is it possible that the 3.7V motor is already being driven with a PWM signal? You say the motor is driven with a variable voltage from 0V to 3.7V. What does this voltage come from? If that voltage is already a pulse-width-modulated 3.7V DC supply, your multimeter will measure it as though it's...
  3. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    I just noticed something in the PIC16F627A data sheet. On page 38 of revision G (DS40044G) there's a grey box that says: "Note: If a change on the I/O pin should occur when a read operation is being executed (start of the Q2 cycle), then the RBIF interrupt flag may not get set." This warning is...
  4. KrisBlueNZ

    How do I build a Metal Detector?

    OK, if it works, it works. If it's running at a few hundred Hz, that explains the 2.2 µF capacitor. I don't think it is detecting a change in the coil's inductance; maybe its saturation characteristics are being affected. Whatever the case, if it works, fine. My suggestion about separating the...
  5. KrisBlueNZ

    Next/previous switching a multiplexer

    Skew is a delay, but in this case it's shorter than one bit-time (32 µs), which is short compared to the delay introduced by receiving a whole byte then retransmitting it, which is a minimum of one byte-time (256 µs). Skew causes the data bits in the message to become wider (or narrower...
  6. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    That looks like it might work, but there is no "=|" operator; I think you mean "|=". With that change, it should work. With SPI, there's no distinction between reading a byte and writing a byte (unless the slave has separate read and write enables, and I've never heard of that). So when you're...
  7. KrisBlueNZ

    Motion sensor lighting with a difference

    Just FYI this is the circuit I'm planning on using for the prototype. The motion detector connects to CN1 at the left. This connector has +12V and 0V for use by the motion detector, and the middle pin is the signal from the motion detector, which must swing to +12V when motion is being...
  8. KrisBlueNZ

    PSU Repair - Tevion DVD Recorder

    You have a chicken-and-egg situation because of how the VIPer53 starts up. Referring to the diagram in post #4 on this thread. When power is applied, the drain terminal of the switching MOSFET in the VIPer53 is pulled up to the positive supply voltage by the transformer primary. An internal...
  9. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    You don't need an ISR at all. You could use an ISR to detect the interrupt request flag, clear it, set a flag in a variable somewhere, then return, but there's no point. If you have code in the mainline that's testing a flag, it might as well test the interrupt request flag in PIR1 (or...
  10. KrisBlueNZ

    Needing help with sensor/meter project

    What kind of device do you use to measure this energy? Do you measure it with a multimeter? What units is it measured in? Watts? Hint: If you can't measure it, how do you know it exists? Clearly, you know something that we don't! I would brand it pseudoscience. Claims that use...
  11. KrisBlueNZ

    How do I build a Metal Detector?

    Yes Adam, they look pretty similar. I don't see how it's supposed to work. For a 555 to oscillate, pins 2 and 6 need to swing between 2/3 VCC and 1/3 VCC, but there's a honking great 2.2 µF capacitor there! Perhaps it would work if that capacitor has a very high ESR! I guess perhaps the...
  12. KrisBlueNZ

    Formula to get voltage on circuit

    As you can see, there are several ways of looking at this problem. My brain works best when I can identify a 0V rail, and it's the most negative part of the circuit (in most cases), so all other voltages are positive (or at least, non-negative) relative to it. Which approach is best depends on...
  13. KrisBlueNZ

    How do I build a Metal Detector?

    Where did you get that 555 circuit? I'm surprised that it works at all. Please provide a reference to the page where it's described. The frequencies you quoted, 465 Hz and 411 Hz, they're kHz, right? Using a 7805 regulator is a good idea. I don't know why it's getting hot. What is the peak...
  14. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    It's not normally a good idea to do anything time-consuming in an ISR. Also, any I/O accesses and variable accesses made by an ISR need to be carefully considered. What happens if the IRQ happens while your mainline code is in the middle of an SPI communication to that IC? Or a different SPI...
  15. KrisBlueNZ

    LED 1.5Vfd???

    Good point. Good point #2.
  16. KrisBlueNZ

    Help please

    I guess Mr. Phillips must have died of hypothermia!
  17. KrisBlueNZ

    LED 1.5Vfd???

    Ah, that makes sense. Measuring the Vf of the LED without the LED being in-circuit is bound to give misleading results! If the open-circuit voltage is 24.5V there could be a constant current circuit, as you say, especially if the brightness is variable, as a gimmick - my Aardvark brand external...
  18. KrisBlueNZ

    LED 1.5Vfd???

    This is pretty interesting. Does the LED look just like a standard one? Or is there a tube that could have some circuitry in it? If there's anything unusual about it, could you post a close-up of it?
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