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  1. KrisBlueNZ

    HELP: CCFL (LCD Backlight) Driving Circuit

    Sorry, BC677/679/681 was a typo; BD677/679/681 was what I meant. So you're right. Your opinions on the pin allocation could be right; I really couldn't tell you. The standard way these CCFL transformers are driven, they only need one primary and one secondary, not even a feedback winding. The...
  2. KrisBlueNZ

    Comparator inputs

    Here's a corrected version. I've connected the shunt straight across the transformer in the usual way, and used a voltage follower stage as a buffer for each transformer. You might be able to get away without the buffer stage at all, with a few component value changes later in the design, but...
  3. KrisBlueNZ

    Comparator inputs

    Oh ****! You're right. I'm really sorry! Yes there will be interaction between the two inputs because of the current flowing in the current transformer, which will affect the bias rail. I didn't think clearly about this when you described the problem. You're absolutely right. Please accept my...
  4. KrisBlueNZ

    Momentary closure (20ms), wait 1 second, and momentary close (20ms)

    The inductor marked L1 represents the coil of the reed relay. The contacts of the reed relay aren't shown; they need to be connected across the start/stop pushbutton in the controller. Sorry for not being clear about this.
  5. KrisBlueNZ

    HELP: CCFL (LCD Backlight) Driving Circuit

    The 2SC1983 is a 3A, 60V Darlington NPN. Suitable replacements would be BC677/679/681 which are available from Digikey and almost certainly from Mouser, Fry's and others. Edit: Oops, you're in the Midlands. That sounds like it's somewhere in the UK. Try Farnell aka Element14. CCFL inverters...
  6. KrisBlueNZ

    Momentary closure (20ms), wait 1 second, and momentary close (20ms)

    This diagram is a bit clearer. I've changed CT to a 1 uF capacitor, either a surface-mounted multi-layer ceramic, or a through-hole part (probably better), and replaced RT with a 680k fixed resistor in series with a 500k trimpot. Set the trimpot to get exactly the required delay between the two...
  7. KrisBlueNZ

    Momentary closure (20ms), wait 1 second, and momentary close (20ms)

    Here's a nice simple circuit that should do what you want. The 555 is connected as a monostable. When you trigger it by closing the switch connected to pin 2, its output (pin 3) goes high (to +12V) and about a second later, returns low. The time is proportional to the product of RT and CT...
  8. KrisBlueNZ

    Momentary closure (20ms), wait 1 second, and momentary close (20ms)

    What power supply voltage(s) are available? 12V would be good
  9. KrisBlueNZ

    home security system

    Don'tcha just LOVE questions like this. Simple. Just connect them all together. (Sorry, I couldn't resist.)
  10. KrisBlueNZ

    multiple displays

    Gorgon's first paragraph hits the nail on the head regarding using a current loop and connecting the meters in series. If the meters have a 10 megohm input resistance in voltage mode, connecting 22 of them in parallel will give a combined input resistance of 450 kilohms, which is still pretty...
  11. KrisBlueNZ

    Momentary closure (20ms), wait 1 second, and momentary close (20ms)

    I would use a reed relay, driven by a transistor that is driven by a monostable (e.g. a 555) in such a way that it activates the relay briefly on both positive and negative changes on the monostable output. You press a button to trigger the monostable; the transistor activates the relay...
  12. KrisBlueNZ

    What's it called!

    Normally-open momentary pushbutton or switch
  13. KrisBlueNZ

    Heathkit O-11 Oscilloscope Repair

    You could TRY to sell it to an antiques dealer. Good luck! Is it really a 60 MHz scope? I doubt it, based on the schematic diagram. Perhaps the eBay seller was being a bit... creative. That design has many weaknesses, and I expect poor bandwidth would be one of them. Dual trace is very useful...
  14. KrisBlueNZ

    Heathkit O-11 Oscilloscope Repair

    V9 is the rectifier for the negative rail for the CRT cathode. It does have a separate filament power supply, which could have become disconnected I suppose, but most likely it's cracked. It's just a diode so you could replace it with any diode that's rated for a few kilovolts. Some adjustments...
  15. KrisBlueNZ

    Cottage industry microcontrollers

    Hi woodchips, If you haven't looked at the AVR, you should. It's not too bad, as 8-bit architectures go. But I'm not sure why you feel the need to change. If the PIC is still doing what you want, what's not to like? Of course moving to a newer device could probably enable you to eliminate...
  16. KrisBlueNZ

    Heathkit O-11 Oscilloscope Repair

    If one of the tubes isn't glowing, the most likely cause is that it's lost its vacuum because the glass is cracked somewhere. Compare it to a similar tube and see if you can find a round area on the inside of the glass that's shiny on the good tube, but grainy and white on the faulty one...
  17. KrisBlueNZ

    Seagate 40gb Hard disk motherboard problem

    If you do a board swap, I believe you'll also need to move the original Flash ROM to the new board, since the fimrware stores information in there that relates to the physical characteristics of the drive hardware. Edit: Or the data might be stored in a SerialFlash or EEPROM
  18. KrisBlueNZ

    Hall Of Lame

    Oh yes. Those guys have real talent for stupidity and stubbornness. Raven Luni, you never had a chance :-) Very true. Unfortunately the entertainment aspect only begins after the frustration has abated. But it's a gift that keeps on giving, so overall they are a positive thing I suppose :-)
  19. KrisBlueNZ

    Hall Of Lame

    Hall Of Lame (or Evidence Of The Dunning-Kruger Effect) For your amusement I present a collection of links to some humorously uninformed, arrogant and communication-impaired forum users that I have had the misfortune of encountering. (For more information see...
  20. KrisBlueNZ

    How can the new Yamaha HH65 Hi-Hat Pedals be modified to work with the Yamaha DD-50?

    Let's assume they're right about that until we find out otherwise.
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