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  1. KrisBlueNZ

    Is YouTube hacked?

    Banks may be insured, but that doesn't mean that the scammers don't make money; it just means the banks don't lose money. The money that the scammers make comes from somewhere. If the insurance is government-funded, it's the taxpayer that's paying the scammers. So the banks, who are in the best...
  2. KrisBlueNZ

    Is YouTube hacked?

    Make sure you use NoScript or some equivalent if you like to rubberneck at hacked sites :-)
  3. KrisBlueNZ

    need help with a speed variator

    Excellent advice Steve! I nominate that post for "valuable tutorial" status!
  4. KrisBlueNZ

    need help with a speed variator

    https://en.wikipedia.org/wiki/Flyback_diode Yes, the 1N400x diodes do have a high surge capacity. Although they're only rated for 1A continuous forward current, they can conduct much higher currents for a short time, i.e. a surge, without damage, which may be important for D4 in your diagram...
  5. KrisBlueNZ

    UFO (undentified flat object)

    Very nice! You could make a nice constantly changing colour display with that. Make three sinewave or triangle wave oscillators all running at different very slow frequencies, and use them to control the brightness of the three colours.
  6. KrisBlueNZ

    Microwave Transformer Isolation

    I've never heard of a microwave oven transformer being an autotransformer. That would be unsafe and illegal. The anode of the magnetron connects to the microwave oven's metalwork. If the transformer was an autotransformer, there would be a path from mains phase and/or neutral to the case.
  7. KrisBlueNZ

    Please suggest a high to low level translator/ shifter.

    Have a look at http://www.digikey.com/product-search/en/integrated-circuits-ics/logic-translators
  8. KrisBlueNZ

    need help with a speed variator

    With the 220 ohm base drive resistor, the TIP33 should be able to switch 0.5 amps, maybe 1A. That corresponds to 12W to 24W for a 24V motor. Modern designs would use an N-channel MOSFET instead of the TIP33. These have lower losses, and are easier to drive, than bipolar transistors. You can use...
  9. KrisBlueNZ

    Help Googling circuit names!

    A circuit that generates a pulse of a specific duration is called a monostable. They can be implemented in many ways - 555, CD4528/4538/4098, 74HC123, using capacitors and gates, capacitors and discrete semiconductors, op-amps... Generally they are triggered from a specific edge on an input...
  10. KrisBlueNZ

    Building a circuit

    Well, there's the BAV99: two signal diodes connected in series in a SOT-23 package. That's what I would use if I was designing a product for SMT manufacture.
  11. KrisBlueNZ

    Building a circuit

    You mean the two series diodes? If there is such a thing as a high-current diode that has a 1.4V forward voltage at a few milliamps, it will be huge and expensive.
  12. KrisBlueNZ

    Building a circuit

    PWM motor controller with slow ramp-up OK, here's my design. I think it will do what you want. It's not simple, and not really a beginner's project. It's up to you whether you want to tackle it. If not, don't worry that I've designed this for nothing... it will be useful as a reference for...
  13. KrisBlueNZ

    Building a circuit

    Chris, you know me so well :-) Yes, my suggestion is to use two 555s, or a 556. One oscillator generates the ramp-up and ramp-down, and the other generates the triangle/ramp wave to control the PWM. Edit: Generation of the final PWM waveform requires some kind of voltage comparison between the...
  14. KrisBlueNZ

    need help with simple 3v to 34v transistor relay/switch

    What about reading the data sheet?
  15. KrisBlueNZ

    need help with simple 3v to 34v transistor relay/switch

    Yes, that's right. But the PICs (some of them, at least) have weak pullup and weak pulldown resistors built-in; you just need to enable them in firmware.
  16. KrisBlueNZ

    ADVREF pin current draw?

    You're right eem2am, the TLV431 is specified for a minimum "cathode" current of 100 uA. It also has a 1.24V reference voltage, instead of 2.5V. Thanks for the heads up.
  17. KrisBlueNZ

    Modification of anti-bark control circuit - help please!

    I don't think putting a DC voltage on the mic preamp is a good idea. Just try yelling into it.
  18. KrisBlueNZ

    Building a circuit

    Thanks Chris :-) I know you like my designs. Regarding jumping into microcontrollers, I think it depends a lot on the person. Age is a big factor. If I hadn't got involved with micros at school, and carried it on, I would be daunted by the idea of embedded systems design now. Although in many...
  19. KrisBlueNZ

    Building a circuit

    Fair enough mate :-) Yes it's true, I think fully discrete can be fun. Yes, I saw the steps too. I just thought that a ramp might be better, since it's simpler to implement (if you don't have programmability). Fair comment about zero hardware cost for a PIC programmer. But for someone who has...
  20. KrisBlueNZ

    rain warning device

    I'm not surprised about the extra tracks. I was trying to picture that board with a raindrop on it... it wouldn't be able to bridge those tracks; they're too far apart! Is it just bare copper?
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