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  1. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    OK, that's a boost converter based on a relaxation oscillator. It will waste significant power because the regulation consists of a zener clamp across the output, instead of a circuit that reduces the drive to the inductor. Also you're running the 1N5819 pretty close to its voltage limit. But it...
  2. KrisBlueNZ

    Adding Aux input to older car stereo

    OK. It's pretty easy to hack it into any of the inputs to IC201, the input selector and volume control IC which also provides front and rear outputs from stereo input sources. I've assumed you want to hack it into the radio signal. The mod is on the "Main Block" section of the schematics, in the...
  3. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    It would be easier if you posted a screen capture of the schematic, along with simulation waveforms. Your best option is a boost converter - a switching supply that uses an inductor in flyback mode to produce a higher output voltage. These are available preassembled on eBay with adjustable...
  4. KrisBlueNZ

    Choosing an Opto Isolator

    Cool. You understand that this all relates only to the release of the solenoid, right? The zener allows the solenoid to release more quickly; it doesn't affect the solenoid pull-in at all.
  5. KrisBlueNZ

    Characteristics of Mixer

    Those amplitudes are far too high. Try reducing them both to around 0.02V peak-to-peak. Or for a clearer output waveform, try setting them to integer multiples, and different amplitudes. For example, try this: VX: f = 40 kHz; amplitude = 0.04V p-p; VY: f = 200 kHz; amplitude = 0.01V p-p. This...
  6. KrisBlueNZ

    Characteristics of Mixer

    Hello and welcome to Electronics Point :-) It's not a square wave; it's a very badly clipped sinewave. My guess is that the transistor is being overdriven and/or is incorrectly biased. Try reducing the amplitude of the VX and VY generators. If you still have problems: 1. What is the frequency...
  7. KrisBlueNZ

    reading / writing samsung K4H511638J

    I doubt I can help but I'm a bit confused by the part number, K4H511638J, which appears to be an SDRAM, not any type of bootable NV storage. Are you sure this is the device that has become corrupted? Is there a Micro SD card, maybe? If so, maybe you could remove it and read it in a computer or...
  8. KrisBlueNZ

    Doubt in two's complement

    The extra '1' you added at the start is the carry bit; it is not part of the result. The one's complement of 000 is 111. If you add 001 to 111, you get 000 with a carry. You need to use a consistent bit width. If you allow your answer to be four bits wide, as in the example of adding 001 to...
  9. KrisBlueNZ

    Doubt in two's complement

    The two's complement (that's the right way to spell it) of 0 is 0. In signed integer arithmetic, +0 and -0 are the same thing: 0. Converting 0 to its negative leaves it at 0. https://en.wikipedia.org/wiki/Two%27s_complement
  10. KrisBlueNZ

    Adding Aux input to older car stereo

    There was a thread a while back where the guy had bought an after-market unit that pretended to be a CD changer but played MP3s - just what the OP wants. He had bought it through eBay. It never worked properly. So be wary of buying anything that's not made by the manufacturer that made the main...
  11. KrisBlueNZ

    Which type of large decoupling capacitor for amplifier audio output?

    Yes, you're right Bob. It looks like 1000 µF would actually be plenty. Thanks for the correction.
  12. KrisBlueNZ

    Whats this please?

    It's not unusual for a crystal oscillator to stop running if you put your finger on one side of the crystal. It's a sensitive part of the circuit, and stray capacitance will affect it. It's probably not a fault. What is the actual fault with the boards, if any? How are they used?
  13. KrisBlueNZ

    Sequential Timing Circuit

    Yes, there's a prototyping area on the board.
  14. KrisBlueNZ

    Sequential Timing Circuit

    The 8-pin device, using an external crystal, has four GPIOs, one of which must be an input. That would be one input for the pushbutton and three outputs for the LEDs. The 14-pin device, using an external crystal, has ten GPIOs, one of which must be an input. That would be one input for the...
  15. KrisBlueNZ

    Sequential Timing Circuit

    No, it has DIP positions. Literally anything in the PIC family will be fine. Based on cost from Digi-Key, the two clear options are: PIC12F1571 http://www.digikey.com/product-detail/en/PIC12F1571-I%2FP/PIC12F1571-I%2FP-ND/4739307 USD 0.77 1-up; USD 0.52 100-up; enhanced mid-range architecture...
  16. KrisBlueNZ

    Choosing an Opto Isolator

    What do you mean? Can you explain why you think an MOV is better than a zener diode?
  17. KrisBlueNZ

    Sequential Timing Circuit

    I would be very surprised if any of those issues was a problem for this project. Arduinos run at a similar speed to the simple PICs - plenty fast enough - apart from the more advanced Arduinos, which run faster. The screen may be slow to update, but not compared to the time periods you're...
  18. KrisBlueNZ

    Sequential Timing Circuit

    OK, I think a good place to start would be to make a provisional choice of microcontroller - at least the architecture. Microchip PICs are very popular, are fairly easy to program in C, and have plenty of examples and tutorials. Many people here have experience with them, including me, Steve...
  19. KrisBlueNZ

    Sequential Timing Circuit

    A microcontroller is definitely the "proper" way to do this. You can get everything you want with a small (8-pin or 10-pin) microcontroller, a crystal (for accurate timekeeping), a pushbutton for reset, and some LEDs with current limiting resistors. The circuit could be powered from a 6V...
  20. KrisBlueNZ

    1 print("Hello World");

    Hi there and welcome to Electronics Point :-) Thanks for the introduction!
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