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  1. KrisBlueNZ

    Lights activted by reed switch

    If you want to buy from Jameco I'd suggest the Fairchild FQP50N06, Jameco catalogue number 785590. It's in a TO-220 package so it's easy to work with, it seems to be ex stock and it's only USD 0.99. It's rated for 50A which seems like a huge overkill, but it's pretty cheap, and you're only...
  2. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    That schematic is a redacted version. It shows some of the important stuff that I'd already figured out, but the details of the microcontroller connections are missing. They are shown as grey boxes, without even part numbers or pin numbers. This schematic has been produced because someone -...
  3. KrisBlueNZ

    What value of resistors do I need and a sanity check

    Hi Zaid. A current regulator is the same thing as a current limiter. Current in a circuit, and its interaction with voltage and resistance, is a little difficult to explain. Your second attachment is actually the same as the design in post #45, but it uses an NPN transistor, so it looks...
  4. KrisBlueNZ

    Hi new here, CRT TV question..

    Nice work! It's good to see someone who has some initiative and makes sensible and safe choices. If that arcing is just on the surface of the LOPT - perhaps caused by dust and dampness on the top surface of the circuit board - you may be able to clean it up and apply some silicone sealant and...
  5. KrisBlueNZ

    How can I control a DC 12V motor

    This MOSFET looks suitable: http://www.digikey.com/product-detail/en/IPP065N03L%20G/IPP065N03LGIN-ND/1996760 You need to program your MCU to generate a PWM (pulse width modulated) signal. Many PICs have a built-in PWM generation circuit. Your PWM cycle frequency should be roughly in the range...
  6. KrisBlueNZ

    Lights activted by reed switch

    Reed switches are available with normally closed contacts and changeover contacts. If you use one of these, you don't need a relay or any other circuitry; just connect the normally closed contact in series with the LED strip. This one is rated to switch 500 mA - make sure your LED strip doesn't...
  7. KrisBlueNZ

    Apple Magsafe

    I wasn't actually suggesting any crowbar action, although that's possible as well. I was thinking that when the control IC has already reduced its output duty cycle below some minimum value, and the voltage feedback circuit is still telling it that the output voltage is too high, the control IC...
  8. KrisBlueNZ

    Help with Jumbotron

  9. KrisBlueNZ

    current flow

    That's right. I'm glad you've figured it all out. One last thing. Op-amp power supplies are normally shown with positive at the top and negative at the bottom.
  10. KrisBlueNZ

    Re: Arduino – Attiny84

    Yes, probably. It depends how much current you will be drawing out of the ATtiny84's outputs, since the device itself doesn't draw much current for its own operation. You should limit the gate current drawn by the MOSFETs by adding a series resistor. For example if the ATtiny is rated for 20 mA...
  11. KrisBlueNZ

    current flow

    Your comment in post #12 about the diagram with the inputs exchanged "working and showing correct values even it is not inverting amplifier" does not make sense and does not explain why the marked values are correct for an inverting amplifier when the inputs are exchanged. In your latest...
  12. KrisBlueNZ

    FOG MACHINE PCB FAULTY

    Not really. It would be possible to go further if we at least had a schematic, but tracing a schematic from a board isn't easy and requires some experience. With a schematic you can compare voltages on a good board and a bad board and we should be able to figure out which difference is causing...
  13. KrisBlueNZ

    How to break a faulty wireless keyboard and mouse.

    You have now invalidated your warranty and thrown away your moral advantage. Your retailer would be within their rights to refuse responsibility for fixing your deliberate damage. Whether they can show how the damage was caused, or whether they search for and find this thread, or whether...
  14. KrisBlueNZ

    Help with Jumbotron

    Each component has six leads and contains three LED elements. You need to connect these three elements in series, with the cathode of one to the anode of the next, using two slightly diagonal tracks. This will form a single functional LED with a forward voltage of 9.6V nominal (voltages in...
  15. KrisBlueNZ

    Help with replacing component on circuit board

    It's not just a good idea for that reason. It minimises force on the soldered connections to the device pins. This is a very good idea, since pins on hot components are already prone to dry joints. So it's also best for long term reliability.
  16. KrisBlueNZ

    Learning to use programmable integrated circuits

    Yes it's a great line! It's not my idea though. That's why I put quotation marks around it. http://c2.com/cgi/wiki?DifferenceBetweenTheoryAndPractice
  17. KrisBlueNZ

    Trying to Increase the Voltage Output of a Boost Switch Mode Supply

    I guess so, but low-value metal film resistors are readily available; I would use one of those. Something like 0.1 ohms, as Steve suggested, would be appropriate.
  18. KrisBlueNZ

    power electronics

    Perhaps he's talking about phase angle control in SCR light dimmers and the like. If so, I guess the firing angle would refer to the number of degrees at which the SCR "fires" (is triggered), relative to the start of the half-cycle, and the conduction angle would refer to the total angle for...
  19. KrisBlueNZ

    Trying to Increase the Voltage Output of a Boost Switch Mode Supply

    A few random thoughts. I've had good results with the UC3845 current-mode controller for the flyback topology. I've always used it with a transformer, but I'm sure it would work as a boost converter too. Its power supply voltage requirements may be too high for you though. Sensing the inductor...
  20. KrisBlueNZ

    Low voltage sine wave output

    BobK, nice work! (BTW your output is 10V p-p; you could manage with a single-ended output stage, and a dual op-amp.)
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