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  1. KrisBlueNZ

    Buck Converter Calculations - Halp!

    Here's my suggestion for an output stage for your supercap charger. It's a combination of the bootstrapped drive circuit you found, and a standard buck regulator with load current sensing. I've added a buffer stage and some protection components. I suggest you build it and play around with it...
  2. KrisBlueNZ

    required delay before function execution!!

    OK. So there's something about the environment that it's installed in that is causing incorrect measurements. This sounds like a hardware issue to me. The screening may need to be improved, or the cable to the transducer may need to be moved away from sources of interference. You might think...
  3. KrisBlueNZ

    Compatibility serial devices

    OK. This tells me that the receiver in device #1 expects RS-232 polarity/inversion, i.e. negative voltage or logic low = idle line, and positive voltage = break state. The CMOS output from device #2 will have the opposite polarity/inversion, i.e. idle high (you can check this with a voltmeter)...
  4. KrisBlueNZ

    My New Toy

    Nice one Chris! I would love something like this, but Wellington is not a very cyclist-friendly city. I live on a hill, about 300m above the city. I wish you many happy hours of cannoodling around on it :-)
  5. KrisBlueNZ

    Control circuit

    Mobile phones have their own charge control circuit that stops charging when it decides that the battery is full. A mobile phone "charger" is just a power supply that the phone can use to charge its battery if it wants to. Or are you talking about charging a separate battery, not the mobile...
  6. KrisBlueNZ

    Control circuit

    Maybe it's hard to say your post is too short there are no periods it's hard to read you ran five sentences into one it's messy you need to give much more information. Edit: the post that this post was a parody of appears to have been deleted.
  7. KrisBlueNZ

    Compatibility serial devices

    Hi Maarten. To be able to communicate serially between two devices, you need compatibility on several levels. Obviously you need a matching protocol, baud rate and framing (number of data bits, stop bits, and parity), then you need electrical compatibility, which includes voltage, but also...
  8. KrisBlueNZ

    Denser than Osmium

    Well, he's realised how difficult he was to communicate with, and apologised, so I consider the matter closed. I agree donkey. It really p*sses me off when people make no effort, and when they just will not co-operate. Also sometimes they will INSIST that even though they know they're a...
  9. KrisBlueNZ

    Control circuit

    OK. Not enough information but it's a start. If you use the method you described, you are cycling the battery. If the power fails when the battery is near its low voltage cutoff point, the charger won't be able to charge it, and either (a) the load will over-discharge the battery, or (b) you...
  10. KrisBlueNZ

    Control circuit

    I get what you're doing. My question is, why?
  11. KrisBlueNZ

    Control circuit

    To see some examples of LED indicators for battery voltage, Google battery voltage indicator LEDs lead acid I assume your "24V" battery is actually 27.6V. If it's a lead-acid chemistry, you should not allow its terminal voltage to drop below about 21V. Batteries are also sensitive to...
  12. KrisBlueNZ

    Analog signal to modulate LED intensity

    That's an interesting device, but not very useful for what you want to do. If you're making an EEG, then you need to be extremely careful with isolation. You will need a very robust isolation barrier, and you will need to pass power across the barrier (to the circuitry on the "patient" side)...
  13. KrisBlueNZ

    assistance with modifying pc power supply

    As BobK has pointed out, you can't connect the TV between the +12V and -12V outputs because the -12V output can't supply much current at all. You can use the +12V outputs from two power supplies, connected in series, IF at least one of the power supplies doesn't have its 0V output rail...
  14. KrisBlueNZ

    What are the advantage and disadvantage of Darlington pair?

    Look at the relevant Wikipedia article. If you can't find two clear advantages and two clear disadvantages there, there's no hope.
  15. KrisBlueNZ

    required delay before function execution!!

    If your converted values are noisy, I would first try to find out why they're noisy and fix that problem, and if I couldn't fix the cause of the problem, apply some filtering or smoothing to the digital value so that brief wrong values can be filtered out. First I would try to characterise the...
  16. KrisBlueNZ

    2M+ ohm resistors not resisting

    Cool. Then the only issue is the reliability of your mod. You know what will happen if your extra resistor does become disconnected... the output voltage will shoot up to about 45V. If you're confident that it can't get disconnected or broken off if you bump the board, or with vibration, then...
  17. KrisBlueNZ

    2M+ ohm resistors not resisting

    Cool. You're welcome, apology completely accepted. Now, as I said before, the regulator may not meet its full specifications at 24V. The components (specifically, the big inductor) were chosen for an output voltage range of 35V upwards, and it COULD make a difference. Things you should check...
  18. KrisBlueNZ

    2M+ ohm resistors not resisting

    OK here are my calculations. With the trimpot wound down to 0 ohms you get about 35V out, right? Vout ----------\/\/\/\/--------\/\/\/\/---------------\/\/\/\/----------GND . . . . . | . . Trimpot . . . . R1 . . . . | . . . . R2 . . . . | . . . . . | . . . . 0 . . . . . . .10k . . . .| . . ...
  19. KrisBlueNZ

    Computer Power Unit Failure

    It's covered with a rubber shield because it can dissipate a huge amount of power if the MOSFET fails short, and you don't want it exploding and splattering all the other nearby components! As for the value, I don't know. I've never seen a resistor marked 5 gold 3 4 silver before. It doesn't...
  20. KrisBlueNZ

    required delay before function execution!!

    Hi Paddy, This should be able to be solved fairly simply, without any multi-tasking or timer interrupt logic. Are you measuring your 4~20 mA signal using the microcontroller's 10-bit ADC? How do you decide when to read the ADC? Are you using a timer, and sampling the ADC at regular...
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