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  1. KrisBlueNZ

    Resistance heater.

    Four 12Ω resistors in parallel will give a combined resistance of 3Ω. If you connect 12V across them, each resistor will have 12V across 12Ω so 1A will flow and it will dissipate 12W. Four of them like this will dissipate a total of 48W.
  2. KrisBlueNZ

    Rain Sensor Status

    Right, well that fits with my suggestion - the "C" pin would probably be the circuitry's 0V rail. But in that case I would expect to see DC voltage on the "RS" pin when the rain sensor switch is open, not AC voltage. But the point is we don't really know, so now we know the full story, the best...
  3. KrisBlueNZ

    Help identifying blown component

    Hi Ross and welcome to Electronics Point :) It's a coated wirewound resistor, probably rated around 5 watts. You may be able to measure it wih a multimeter on resistance range if the wire hasn't actually gone open circuit or been damaged. It would not have been connected across the AC input...
  4. KrisBlueNZ

    Rain Sensor Status

    OK, thanks for the link to the irrigation controller. I guess you want to monitor the status of the Hunter Mini-Clik or Rain-Clik sensor, right? The sensor provides a dry (pun not intended) contact, i.e. a contact that's fully isolated from everything, and the irrigation controller will test...
  5. KrisBlueNZ

    Oscillator circuit LC

    That's fine. Well, there are lots of ways to make an LC tank circuit oscillate. Check out this image search: http://www.google.com/search?q=lc+oscillator&tbm=isch A common result there is the op-amp-based circuit, which is the op-amp-based "negative resistance" circuit (see...
  6. KrisBlueNZ

    Oscillator circuit LC

    Hello and welcome to Electronics Point :-) I'm not aware of any IC that's designed to make an LC circuit oscillate, though there are many circuits using op-amps and other devices. But can you start by telling us the frequency range that the circuit needs to operate over?
  7. KrisBlueNZ

    Designing a Time Delayed Relay

    It's my pleasure :-)
  8. KrisBlueNZ

    Can I use a resistor as a fuse?

    If you're talking about standard zero ohm resistors... ... then no, they're not fusible! Perhaps you have a part number to check?
  9. KrisBlueNZ

    Logitech x-540 repair

    Hi David and welcome to Electronics Point :-) This is a pretty recent product and I doubt that technical information will be available anywhere. I've looked on elektrotanya, a good source of service manuals, but it's not listed there. If you can get any service information on it, that would be...
  10. KrisBlueNZ

    Rain Sensor Status

    Yes, the cap that smoothes the rectified control voltage, C3 in post #64, is much higher than it needs to be. I must have missed this thread completely. Now, coming in with fresh eyes, I can see that the circuit doesn't need to be very complicated at all. No regulator is needed for a simple...
  11. KrisBlueNZ

    Designing a Time Delayed Relay

    You have a GREAT attitude! It's a pleasure to help you. I must have missed that thread completely! Yes I have a lot of thoughts. I'll post there soon. Yep, good idea. View just the overlay, or just the overlay and the pads. That will cut through the confusion so you can see any problems easily.
  12. KrisBlueNZ

    Designing a Time Delayed Relay

    I think that looks great! I'm really impressed. I think it's definitely ready to go off to the PCB manufacturer for checking.
  13. KrisBlueNZ

    Newbie

    Hi Ainzi and welcome to Electronics Point :-) There are lots of electronics tutorials and DIY electronic projects on the web. Just Google some relevant keywords like electronics beginner tutorials projects. There is also a lot of material out there that has been written by people who don't...
  14. KrisBlueNZ

    Designing a Time Delayed Relay

    12 thou is probably OK. The highest voltage across the ground plane clearance will be 48V. Perhaps 15~16 thou would be wise. You can probably move things around slightly to make room for the ground plane around the right Allegro chip. But if you have ground plane on the other side in that area...
  15. KrisBlueNZ

    Designing a Time Delayed Relay

    You should be able to get a 15 thou track through those gaps, and that's plenty wide enough. There's a decoupling capacitor right next to the Allegro chip, which gives it a good firm supply rail to work from and negates any problems due to resistance and inductance in the track. Have you viewed...
  16. KrisBlueNZ

    Designing a Time Delayed Relay

    Yes, that's probably a good idea. Print the board at 1:1 and glue the printout to some expanded polystyrene, and shove all the components through it, or something like that. Good idea. I think you could keep the VCC track to the right hand Allegro chip further away from the edge. I would...
  17. KrisBlueNZ

    Help with MOSFET switching circuit

    Steve, he has a 12V rail available, so he can use a gate driver. Do you have a recommendation?
  18. KrisBlueNZ

    Help with MOSFET switching circuit

    You can take it from here Steve
  19. KrisBlueNZ

    Help with MOSFET switching circuit

    PWM at what frequency? Do you have a higher voltage supply rail available?
  20. KrisBlueNZ

    Help with MOSFET switching circuit

    Yes, a logic-level MOSFET is probably the answer. There are some pretty impressive ones around now, like the Alpha & Omega AO4402: http://www.digikey.com/product-detail/en/AO4402/785-1549-1-ND/3621495 It comes in an SO-8 package with the standard pinout, so there are lots of drop-in...
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