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  1. KrisBlueNZ

    Woo-woo projects.

    LOL! ... at least I said "apparently ..." :-)
  2. KrisBlueNZ

    Woo-woo projects.

    I just stumbled on an article apropos this thread. Apparently this advice about "Eleven things you don't learn in school" was given in a speech by Bill Gates to high school students (probably in the 1990s, going by the reference to "car phone"). "He talks about how feel-good, politically...
  3. KrisBlueNZ

    Alarm reset timer

    Personally I would hack something onto the circuit board of the PIR device itself. It already has the low-voltage supply and the relay. It would only take a few components. The problem is that we would have to trace out at least part of the circuit in order to know how to modify it. If you're...
  4. KrisBlueNZ

    High Voltage Regulator Circuit Help

    NantachieRat, Duke and BobK are pulling your leg. I think they know that you mean 500 milliamps, but you wrote 500 MA, which is 500 mega-amps. 500 milliamps should be written 500 mA. The difference is important; we are engineers here.
  5. KrisBlueNZ

    Simple MIC Buffer Design Question

    Thanks for your kind comments :-) That mic looks like a good solution for your needs. But you should investigate how the response compensation is performed. Presumably the correction will need to be done in software. The question is: are the compensation parameters specified by the...
  6. KrisBlueNZ

    Just like to say....

    I think Ron H is a lot more than a 555 wizard. But I agree regarding the attitudes there. Perhaps that's because it's a much bigger site than Electronics Point. Whatever the reasons, I'm very happy to be here. We have a wide range of experience and a good attitude, I think.
  7. KrisBlueNZ

    Woo-woo projects.

    Must be powered by water. Actually, HHO. That's what we in-the-know folks call it. People say I think and write in non-sequiturs, but actually, my cat has fleas. You can't tell me that my idea won't work. I haven't explained it in enough detail for you to be sure of that. In fact I haven't...
  8. KrisBlueNZ

    Simple MIC Buffer Design Question

    If the circuit is powered from a 9V battery that is not used for any other function, you don't really need the separate node for the input stage bias. If it's powered from a noisy supply, I would add a series resistor in the positive supply feed to the right of C3, as you suggested. Whether or...
  9. KrisBlueNZ

    Op Amps: Unwanted Oscillations

    Post a schematic AND a photo of the board.
  10. KrisBlueNZ

    Pulsated LD

    That's a very poor description of your project. Start from the basics. What is the overall aim of the project? What is the nature of this "data"? How, and why, do you want to "mark" it into the surface of some wood? What is the nature of the signal? Is it an audio signal? You mention volume...
  11. KrisBlueNZ

    Generate 2ph 60cy 115/115v

    You need a circuit called an inverter. It takes a DC input and generates single-phase AC at mains voltage. Inverters typically run from 12VDC or 24VDC and can supply a few hundred watts. Large inverters can supply power in the kilowatt range. There are two main types of inverters: pure...
  12. KrisBlueNZ

    Help with amp

    Yes. That circuit is a power amplifier. It accepts an input signal at "line level". This is also the signal level that a spring-line reverb or other reverb circuit will operate. You will probably also need a preamplifier, to provide variable gain, tone control, impedance matching, and...
  13. KrisBlueNZ

    Do I need a linear regulator in this circuit?

    The MAX1044 is a switched capacitor charge pump. Its output current capability is relatively low and it's not suitable for charging a USB device such as a smartphone. You can buy a USB charger that operates from a single AA cell - in fact I have one. I haven't tested it properly yet, but I know...
  14. KrisBlueNZ

    Simple MIC Buffer Design Question

    It looks pretty good to me. I might combine Rm1a and Rb1a, and C4 and C5, and take Rm1b and Rb1b from the same node. Also I would check the DC voltage on the microphone and adjust the microphone bias resistor if necessary to get the recommended DC voltage.
  15. KrisBlueNZ

    Relay Testing

    Unconnected (open) contacts should read infinite resistance on every resistance range. This is the same indication you get when the probes aren't connected to anything. Connected (closed) contacts should read close to 0 on every resistance range. This is the same indication you get when you...
  16. KrisBlueNZ

    Need help with a Power Failure Alarm Circuit

    Yeah, they don't seem very friendly. They do have a good resident expert though. Ron H, I think his name is. Very knowledgeable.
  17. KrisBlueNZ

    Need help with a Power Failure Alarm Circuit

    I see. I guess as long as the circuit following the phototransistor or LDR is sensitive enough, it will detect a pretty weak light. I subscribed to AAC as well, but I don't much enjoy it, compared to EP.
  18. KrisBlueNZ

    Using Arduino to read bipolar signal (from plants)

    This is the circuit I suggest. The circuit requires a positive power supply (VP) and a negative power supply (VN). If you want a 0~5V voltage range on the signal going to the ADC, VP must be at least 8V. This is because most op-amps cannot drive their outputs all the way to their positive...
  19. KrisBlueNZ

    some damaged gadget chargers

    Good advice from duke37 as usual. Obvious next step: post some photos here.
  20. KrisBlueNZ

    Need help with a Power Failure Alarm Circuit

    Yes Chris, sorry, I wasn't recommending the line-powered design for this application. I was just pointing out that it's not as dangerous as a half-live circuit. I agree that an optocoupler is probably the best solution for this job. Regarding neons in optocouplers, I guess there would be...
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