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  1. KrisBlueNZ

    Sign with 175 LEDs

    OK that switch is different from what I thought it would be. It has three terminals; two of them are the switch itself, and the third one is for the LED. The page you linked doesn't give enough detail to be sure about this, but I assume the silver-coloured pins are the switch, and the...
  2. KrisBlueNZ

    Sign with 175 LEDs

    All excellent answers from Steve, as usual. I'm a bit confused about the switch. In your schematic in the earlier post, you described it as an "LED rocker switch". Do you mean that it has an LED built in? If so, it probably has two connections for the illumination LED and two or three...
  3. KrisBlueNZ

    Sign with 175 LEDs

    Break one of the wires to the power supply (by convention, the positive one) and connect the switch across the break.
  4. KrisBlueNZ

    Sign with 175 LEDs

    DC. Heat probably won't be a problem. But you can calculate the amount of power dissipated by each component in the sign from the formula P = V I where P is power in watts, V is the voltage across the component, and I is the current through the component, in amps. So for example if your LED...
  5. KrisBlueNZ

    Send data with one wire protocol?

    It's interesting that you say you can't measure the bus low time on the slave. On the master, you need to be able to distinguish a received 0-bit from a received 1-bit, so your code must already be capable of this; as I see it, the major difference between master and slave is that the slave...
  6. KrisBlueNZ

    Sign with 175 LEDs

    Add up the forward voltages, subtract that from the power supply's output voltage. That tells you how much voltage will be dropped across the resistor. Then use Ohm's Law to calculate the current limiting resistance as R = V / I where R is the current limiting resistor value, V is the voltage...
  7. KrisBlueNZ

    Sign with 175 LEDs

    Yes, that's dead right.
  8. KrisBlueNZ

    Sign with 175 LEDs

    If you have a regulated voltage, there is no need for transistors to regulate the current; you can just use a current limiting resistor in each string. The total LED string voltage will be fairly constant, and the power supply voltage is regulated, so the voltage that's left across the resistor...
  9. KrisBlueNZ

    Sign with 175 LEDs

    As far as batteries are concerned, the physics is pretty simple. For a given chemistry, larger volume means more energy available. You can use larger cells, or more cells, or both, to get more energy. Energy is measured in watt-hours (or Joules) and is power multiplied by time. So with more...
  10. KrisBlueNZ

    Pickup Winder Build

    Connect your 12V supply across pins 5 and 4, and connect a wire to pin 2. Touch the other end of the wire on pin 4 and the count should increment. If there's a decimal point showing, you must have a jumper present on the jumper block. Make sure there are no jumpers on it. This is all assuming...
  11. KrisBlueNZ

    Readily Available Energy

    How about these? Peel-and-stick solar cells! Not cheap though, I'm sure. http://www.edn.com/electronics-blogs/tech-edge/4405025/Peel-and-stick-solar-cells
  12. KrisBlueNZ

    Sign with 175 LEDs

    Yes, the LED current determines the brightness. The relationship is not strictly linear. Reducing the current through an LED will also reduce its forward voltage somewhat. You need to take this into account when you calculate the series resistors. For best efficiency you would be better to...
  13. KrisBlueNZ

    can clock to control a stepper motor ?

    That is discussed in the other thread. I don't think a DC motor would be accurate enough.
  14. KrisBlueNZ

    Mains powered SMPS.....Earthing?

    The cap across the isolation barrier is not there "for safety". It's there to improve the operation of the circuit, and that might include improving EMC. But it is critical to safety, because it connects straight across the isolation barrier, which is a safety feature. If it goes leaky or fails...
  15. KrisBlueNZ

    LED VU meter with transistors, dotted...

    Good choice. Good luck!
  16. KrisBlueNZ

    Mains powered SMPS.....Earthing?

    Dave, I think he is talking about switching supplies. The isolating transformer he's referring to is the high-frequency transformer. That's what provides the isolation in an SMPS.
  17. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    OK. You might want to check the maximum clock rate for the cathode driver chips. If you need to use an SPI peripheral, if you're running your PIC at 80 MHz, you may have to slow down the peripheral to meet the limits of the cathode driver chip, so you may not get four times the speed. In any...
  18. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    That sounds promising. I think your calculation is wrong. Each multiplex phase, which will take about 1.5 ms, only updates one slice. So you don't need to multiply your 614 microseconds by 8. (If you do, the answer isn't 1638 microseconds anyway.) This guy who updated 64 LEDs at once in 204.8...
  19. KrisBlueNZ

    Mains powered SMPS.....Earthing?

    In theory, a transformer provides perfect isolation and there is no need to earth the output side. In practice, there are many leakage paths between the primary (live) side and the secondary (output) side and leakage and sometimes breakdown can occur. One example is the capacitor that is...
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