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  1. KrisBlueNZ

    bi directional communication to multiple nodes over 1 wire

    Yes, thanks for the clarification. If you "have experience working with mains", you should know that "using the ground wire in some way" would be very unwise and probably illegal for safety reasons. Luckily, there's nothing useful you can do with it anyway, AFAIK. You will need to use either a...
  2. KrisBlueNZ

    Help to build a device to revolutionise an industry

    Sounds like you want a programmable logic controller (PLC) with analogue inputs. Google it.
  3. KrisBlueNZ

    Options for RC model oscillators?

    I would be comfortable trusting the manufacturer's specifications, after doing an initial test to make sure I was programming it correctly. Of course any device needs an accurate frequency source; if the device doesn't include one internally, you'll need to provide one, and its accuracy must...
  4. KrisBlueNZ

    RS485 signal transmission - LED panels

    Sorry for not reading your first post carefully! Regarding your DMX testing, I don't know why it didn't work. DMX is a unidirectional serial data stream, and converting from RS-485 to logic levels and back should not cause a problem. Can you post a schematic diagram of the circuit you used...
  5. KrisBlueNZ

    clap based volume control

    In what way didn't it work out? It should "work out". Can you explain? Right, that should work too. You might save a bit of space if you use an NPN transistor, connected as an emitter follower, to drive each LED. You'll also find that the whole circuit will work a lot better at a higher...
  6. KrisBlueNZ

    Options for RC model oscillators?

    Yes! Lots of ideas can be found here. But ceramic resonators are typically only accurate to 0.5% so not suitable for this application. Also they are only available in commonly used frequencies. If you had downloaded and viewed some data sheets, as I suggested, you would know that these devices...
  7. KrisBlueNZ

    RS485 signal transmission - LED panels

    I'm not sure what you mean here. All of the shift registers in the first panel are clocked from the same signal, right? So the signal you're feeding into the MAX485 for the clock output to the next panel is taken from the clock input on the last shift register, but it's the same signal as the...
  8. KrisBlueNZ

    Help about a Pluviometer!

    Tipping bucket rain gauges are widely available and can be connected directly to one digital input on the Arduino.
  9. KrisBlueNZ

    Options for RC model oscillators?

    Have a look at http://www.digikey.com/product-search/en/crystals-and-oscillators/programmable-oscillators Download a few data sheets to get an idea of what they do, how you use them, and whether they would do the job.
  10. KrisBlueNZ

    bi directional communication to multiple nodes over 1 wire

    Do you intend to have a separate battery in each LED module? Are you prepared to have a microcontroller in each module? Do you have experience programming microcontrollers? Is there a global ground connection as well as the single wire? Hint: if not, you'll need to use a very high frequency...
  11. KrisBlueNZ

    Current limiter add on

    You can't use a current limiter. A current limiter operates by reducing the output voltage if the load tries to draw too much current; if you do that, the phone will think the charger has been unplugged. It will then stop charging, and the current limiter will then ramp up the output voltage...
  12. KrisBlueNZ

    RS485 signal transmission - LED panels

    Hi Martin and welcome to Electronics Point :-) So you're driving the LEDs using shift registers, and you want to cascade the second panel from the first panel by feeding the serial output of the last shift register on the first panel into a TTL-to-RS-485 converter and converting it back on the...
  13. KrisBlueNZ

    JFET Transistor Biasing?

    Hi commathe and welcome to the Electronics Point forums :) The source voltage in a JFET amplifier stage is created by current flowing through the drain resistor, through the drain-source path within the JFET, and through the source resistor. The JFET controls the amount of current that flows...
  14. KrisBlueNZ

    Design question on microcontroller and TIP122

    OK, fair enough. In that case it's probably most appropriate to switch the positive supply to the modem. You should also make sure that any signal that feeds into the modem is at 0V before you power it down, otherwise it might (possibly) be damaged. You can switch the supply rail using either...
  15. KrisBlueNZ

    what is difference between memory address and memory location

    Very good answer Steve.
  16. KrisBlueNZ

    Design question on microcontroller and TIP122

    I would not be switching the power to a GSM modem. Every time you power it up, it will have to re-establish a connection with a cell site. This takes a while and wastes power. Also of course it won't be able to receive an incoming call while it's powered down, but I assume you don't need that...
  17. KrisBlueNZ

    Design question on microcontroller and TIP122

    If the load is a circuit that needs to have its negative supply connected to the negative supply of the control circuit, then yes, you need to connect the negative rails together and switch the positive rail. This is a common requirement in battery switching applications in cellphones, for...
  18. KrisBlueNZ

    clap based volume control

    The LEDs are probably drawing too much current and loading down the 4017's outputs. Increase the values of the resistors in series with the LEDs. Check that the voltage at the active output of the 4017 is at least 2/3 of the supply voltage. Increase the LED series resistor until it is. The...
  19. KrisBlueNZ

    clap based volume control

    Right. Is that a question? One switch is ON at a time. Each switch connects a different resistance between the input and the output. There is a resistor across the output which I will call RL. The currently selected input-to-output resistor (the one whose switch is ON) forms a voltage divider...
  20. KrisBlueNZ

    what exactly is Voltage

    I agree Bob. Laplace's point is simply that voltage is like gravity in that they are both things that we understand through their effect, not through an understanding of what they are or how they do what they do; we understand only how they cause other effects.
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