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  1. KrisBlueNZ

    Arcade 110v strobe flasher circuit help

    Here's another design using the same principle, but using two 555 timers (or one 556 dual timer). The BOM is quite small - one NE556 dual timer IC, five resistors, two electrolytics, a diode and a relay. The relay must have a 12V coil with a coil resistance of 60 ohms or more (preferably much...
  2. KrisBlueNZ

    LDR circuit.. no luck :(

    The LEDs shouldn't light at all when the LDR is in the light. Can you post a photo of the underside of the existing PCB with the wires soldered onto it, so I can check that you connected them to the right places? Also could you upload a few photos of the top and bottom sides of the stripboard...
  3. KrisBlueNZ

    LDR circuit.. no luck :(

    Great! Good work.
  4. KrisBlueNZ

    Arcade 110v strobe flasher circuit help

    Just in case anyone's interested, I designed and simulated a circuit to do this. It's a bit impractical - lots of discrete components. Mostly I did it to learn more about LTSpice. The circuit uses two oscillators based on the two-transistor Schmitt trigger circuit that I like so much. C1 (the...
  5. KrisBlueNZ

    Help with 74LS170 4x4 Register

    Interesting. Does it cause some sort of latch-up? I'll google some application notes.
  6. KrisBlueNZ

    Help with 74LS170 4x4 Register

    gorgon, where did you get this advice that LS inputs shouldn't be connected directly to VCC? I haven't heard it... AFAIK it's fine to do that. What is the reasoning?
  7. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Having a hard time finding 100 nF capacitors on Mouser? That's like having a hard time finding Cheddar in a cheese shop! "It's the single most popular capacitance value on earth!" (to paraphrase Monty Python). It's also referred to as 0.1 uF, or just "point one" :-)
  8. KrisBlueNZ

    Basic DC theory question

    This circuit is a VOLTAGE DIVIDER. Your resistor and the resistance of the voltmeter are connected in SERIES, across the battery, so there is 12V across the series combination. The 12V is divided between the two resistances according to their relative resistances, with the HIGHER resistance...
  9. KrisBlueNZ

    What value of resistors do I need and a sanity check

    None of the parts in that circuit are really sensitive to ESD, even though some of them may come in protective packaging. The LEDs may be slightly ESD-sensitive; you can protect them by sliding a small piece of conductive foam, or a few coils of a very fine spring, onto the leads, and only...
  10. KrisBlueNZ

    LDR circuit.. no luck :(

    That looks pretty good! I'm not sure about the blue trimpot. Its wires should go straight into the holes. It looks like it's not sitting flat. Also you might want to connect the LDR through a length of cable, unless you're going to extend the three wires from the other PCB. It's easier to cut...
  11. KrisBlueNZ

    LDR circuit.. no luck :(

    Thanks Steve for the link, that's very helpful. I don't think DIYLC is up to the task either, so I've done a layout the old-fashioned way, on paper. This drawing shows the board viewed FROM ABOVE. The copper strips are on the UNDERSIDE of the board, i.e. they're not visible. The components...
  12. KrisBlueNZ

    LDR circuit.. no luck :(

    OK. I'll see if I can come up with a layout using DIYLC. I tried the other stripboard layout programs and none of them are any good, for various reasons. Does anyone have a recommendation?
  13. KrisBlueNZ

    LDR circuit.. no luck :(

    In addition to what Steve said... Google stripboard layout software There are several alternatives. It's probably worth using a program to design your layout. The web pages you find should also describe the general principles of laying out your board. You won't need much board area. There's...
  14. KrisBlueNZ

    RMS transformer voltage.

    How about modifying a PC power supply? Google modify pc power supply 13.8V
  15. KrisBlueNZ

    serial loopback test won't work.

    I agree with gorgon's comments above. But CTS is only checked by software; a general purpose terminal emulator can transmit regardless of the state of CTS, and selecting "NO flow control" should enable this. So you shouldn't have to loop back any flow control signals. And looping things back...
  16. KrisBlueNZ

    RMS transformer voltage.

    I agree with Steve. Trying to jack up the voltage with lots of smoothing will just mess up the power factor even more than necessary, and put stress on everything. I would use a higher secondary voltage with less smoothing, producing say 30~35 VDC, and a switching regulator, with a linear...
  17. KrisBlueNZ

    Volume control to a speaker

    As davenn hinted at, the problem is the amount of power that the attenuator will have to dissipate. The extra energy is dissipated as heat. You need to tell us the kind of power levels you're working with. Even wirewound potentiometers have limited heat dissipation, unless you can find a...
  18. KrisBlueNZ

    LDR circuit.. no luck :(

    No, it doesn't matter if the resistor values are wrong in the diagram of the existing circuit. The extra circuit will still work. Here's a parts list with Jaycar part numbers. It covers everthing below the dotted line. 2x ZT2164 BC557 PNP transistor (Q1,2) 2x ZT2152 BC547 NPN transistor (Q3,4)...
  19. KrisBlueNZ

    Light dimming circuit

    So you need a circuit that is mains powered, that drives a 60~100W light bulb. When you power it up, it starts with the bulb running at 100% power, then gradually dims the bulb until it reaches the percentage that has been set on a potentiometer, and leaves the light bulb running at that...
  20. KrisBlueNZ

    Light dimming circuit

    That explanation is far too brief. Is this a one-off project? What has been decided, and what do you need to decide? For example, do you need to use that light bulb? What is its current or power rating? What's the budget? When is it needed? Can you borrow stuff for it or will it be permanent...
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