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  1. KrisBlueNZ

    Help with Yamaha tuner/amp

    Thanks for the link to the service manual but we can't download it unless we sign up. Could you upload it somewhere where we can get it without signing up. The brown stuff on the filter caps is glue, deliberately put on heavy components to relieve strain on the solder connections. Edit...
  2. KrisBlueNZ

    Low DropOut Regulator

    Yes, lots of people can, and already have! http://www.google.com/search?q=low+dropout+regulator+ldo+advantages
  3. KrisBlueNZ

    Simple NPN transistor circuit help

    Make sure your circuit matches this one exactly (apart from the 2 ohm current limiting resistor).
  4. KrisBlueNZ

    automatic doorbell

    To the OP, Rijoe Mathew. Adam has found a 40 kHz crystal that would make the crystal-controlled transmitter a lot simpler: http://mouser.com/ProductDetail/ECS/ECS-400-125-13X/?qs=sGAEpiMZZMsBj6bBr9Q9aZy59saLb3yqiozJuWTcgkc%3d If you're considering building my circuit, let me know and I will...
  5. KrisBlueNZ

    Garden Wet Play - 12V Solenoid Control System

    Yes, they're pretty cheap and you can get I/O boards for them. I'm sure there would be example code that does the sort of thing you want, that you could modify without too much trouble.
  6. KrisBlueNZ

    Need help with repair

    Hi Trevor and sorry for the delay. I've drawn up the schematic of that board: ("RD" is shown on that diagram as a fusible resistor but it seems clear that it's actually just a fuse.) Fixing this board would involve replacing all the semiconductors, and "RD". This would only be worthwhile if...
  7. KrisBlueNZ

    RC circuit

    There are two arrangements for a simple R-C circuit. Yours has an output feeding through a capacitor to an input, with a resistor from the input to a power supply rail. It's called an RC "differentiator". The other arrangement has the capacitor and resistor exchanged; it is called an RC...
  8. KrisBlueNZ

    Garden Wet Play - 12V Solenoid Control System

    Not necessarily. An I/O board with MOSFET outputs instead of relay contacts would be better, because there's nothing to wear out. It's probably worth waiting a day or two to get some other perspectives and suggestions from other Electronics Point folks too.
  9. KrisBlueNZ

    Garden Wet Play - 12V Solenoid Control System

    I don't think any of it will be easy. I'm suggesting that all the software runs on the host - the laptop or smartphone, or some microcontroller board such as an Arduino. That would include the interfaces to any control devices (smartphones have several types built in), the overall control...
  10. KrisBlueNZ

    Simple NPN transistor circuit help

    Yes, try to figure out exactly what you have. You can change a circuit from using a PNP to using an NPN, or vice versa, by reversing the direction of all polarised components (the power supply, all diodes, and any polarised capacitors).
  11. KrisBlueNZ

    Garden Wet Play - 12V Solenoid Control System

    I think having two levels of programmability ("something that you can just power on and it will carry on cycling patterns etc then more granular control via another interface of some sort") would be an extra and unnecessary level of complexity. If you already have some level of programmability...
  12. KrisBlueNZ

    Solar and Ambient energy conversion

    Hugh, what is the point of your post?
  13. KrisBlueNZ

    Garden Wet Play - 12V Solenoid Control System

    You'll get the most flexibility with a software-based solution. There are many options here, such as an Arduino microcontroller board, a tablet or smartphone driving a bluetooth I/O module, or a laptop driving a USB relay driver board. Do you have any programming experience? What features of...
  14. KrisBlueNZ

    Need a cross reference for MOSFETS

    No problem :-)
  15. KrisBlueNZ

    RC circuit

    No problem. Pin 5 goes negative for a while when pin 3 changes from high to low. Because the capacitor is charged, with the pin 3 side more positive than the pin 5 side. So when pin 3 tries to go low, the capacitor "pushes" pin 5 below 0V and makes the input protection diode on pin 5 conduct...
  16. KrisBlueNZ

    Need a cross reference for MOSFETS

    I think they're diodes, not MOSFETs. Are the two end pins connected together, and directly to a pin on the transformer? If so, this should be a suitable replacement: http://www.digikey.com/product-detail/en/STPS20SM60ST/497-12308-ND/2827132
  17. KrisBlueNZ

    RC circuit

    Yes. Gate A is used as an inverter. Its input is on pin 2 and its output is on pin 3. So pin 3 goes low when the input signal on pin 2 goes high. Yes, negative relative to the 0V rail. More negative than 0V. (BTW that's "zero volts", 0V, not "O V".) Part-way through the high pulse on pin 3...
  18. KrisBlueNZ

    What are these good for?

    Yes, you can do that. You can use them to switch higher voltages too, as long as you provide at least 10V gate-soure voltage.
  19. KrisBlueNZ

    Simple NPN transistor circuit help

    That circuit in post #4 will work. That is a PNP transistor in that diagram.
  20. KrisBlueNZ

    What are these good for?

    It depends. There are several kinds of solid state relays. MOSFETs can't switch AC; if you want your SSR to switch AC then you need a bridge rectifier. And it needs to be able to handle the load current. MOSFETs require significant gate-source voltage to saturate. If you want isolated drive...
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