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  1. KrisBlueNZ

    12v fans, simple question

    Hi and welcome to Electronics Point :) Voltage is measured between two points, like a distance. You could imagine that a 12V power supply "pulls" its outputs (they're normally called +12V and 0V) apart to a distance of 12 inches. The power supply includes regulation, so its outputs are always...
  2. KrisBlueNZ

    Replacement for a microcontroller

    I don't think that would preserve the waveshape, but you could use your low-frequency signal to modulate the frequency or amplitude of an audio-frequency oscillator, feed the oscillator output into the sound card input, and use software to convert it back to its original form.
  3. KrisBlueNZ

    Problem in a circuit?

    A picture paints a thousand words. How about uploading some schematics.
  4. KrisBlueNZ

    Replacement for a microcontroller

    Have a look here: http://www.digikey.com/product-search/en?FV=fff40027%2Cfff801b7%2C3cc0054%2C3cc006e&stock=1&quantity=1
  5. KrisBlueNZ

    Replacement for a microcontroller

    Your sound card will not respond to frequencies that low. But there are USB ADCs that can probably be DC coupled, then read like an external sound card. BTW why is there an LM386 involved? The LM386 is an audio amplifier that's designed to drive a loudspeaker. It will add distortion to the...
  6. KrisBlueNZ

    Micro Moisture Detector

    The basic idea is very simple. You'll need a 3V lithium cell such as a CR2032. A small N-channel MOSFET can do the switching; the quiescent current will be very low. You can use a piezoelectric beeper for the alert - these are available with various options, but they're generally not very small...
  7. KrisBlueNZ

    FET switch circuit - is it correct

    That's getting there. You've fixed the problem with driving the PNP base directly from the micro. R3 doesn't need to be so low. I'd suggest at least 33k. That will reduce wasted current. R2 also doesn't need to be so low. 33k will be fine. R6 will waste about 5 mA. This could be avoided by...
  8. KrisBlueNZ

    FET switch circuit - is it correct

    You're right that the LM317 has a lower "ground" current, but the presence of R4 and R5 will draw 5.2 mA from the 5V rail. So you lose the efficiency that you gained. Olivier recommended an LM1117 which is a low-dropout regulator (a feature you don't need) and has a typical quiescent current of...
  9. KrisBlueNZ

    FET switch circuit - is it correct

    Working from the schematic in post #8. Your simplest option is to replace Q2 with a P-channel MOSFET. Source to emitter position, drain to collector position, and gate to base position. The MOSFET will work just like a PNP transistor except that its gate current is practically zero and its...
  10. KrisBlueNZ

    Modifying an antique camera

    Can you start by uploading some nicely zoomed pics of the board, with the capacitor labelled, including the IC that the capacitor connects to? Both sides of the board are probably relevant. See https://www.electronicspoint.com/resources/how-to-take-photos-of-circuit-boards.6/ A few pictures of...
  11. KrisBlueNZ

    FAN5345

    As Steve said, I would be concerned about that inductor. It looks pretty small, and 1 ohm resistance is pretty high for such a small inductance. I think it's just a signal inductor for noise suppression in medium- to high-impedance applications. Try using one that's rated for at least 1A such as...
  12. KrisBlueNZ

    Help with diagnosing problem with pcb from charge controller

    Upload a photo showing all six of them with the metal bits removed. I will mark up the photo to show you where to measure with your multimeter.
  13. KrisBlueNZ

    Automatically play CD when power comes on

    Hello and welcome to Electronics Point. Have you tried taping the Play button down and turning the unit ON? This might make it start playing automatically. If you test this thoroughly and it works, then you know all you need to do is to bridge the pushbutton terminals. Or you could use a...
  14. KrisBlueNZ

    Next/previous switching a multiplexer

    The pulse stretcher circuit takes its input from a logic-level signal that is referenced to the 0V and +5V rail from which the pulse stretcher is powered. This signal can come from (a) the output of an optocoupler in a MIDI IN circuit, or (b) a logic-level signal elsewhere on the board, such as...
  15. KrisBlueNZ

    Best platform for simple(ish) accelerometer logging project

    A micro SD card is probably ideal for storing the data.
  16. KrisBlueNZ

    What is the purpose of this circuit board?

    OK. You won't be able to reverse-engineer the chip under the blob, but you may be able to make a circuit that will drive those LEDs. Can you upload a photo of the component on the other side of the board, to the right of the black blob in the photo in post #1 So the board connects to a battery...
  17. KrisBlueNZ

    Help me understand my wall wart

    Automatic handling of 115V/230V can be handled in different ways. The simplest way is by designing the circuit to operate at 115V AC (often, down to 100V AC). If the supply voltage is higher, the circuit's normal regulation action will reduce the duty cycle of the signal into the transformer to...
  18. KrisBlueNZ

    Modifying an antique camera

    Just to throw another crazy idea into the mix: Depending on how the capacitor is connected and used by the existing circuit in the camera, you may be able to replace it with a microcontroller that can do precise timing. Once you have a micro in there, your options expand hugely - you could make...
  19. KrisBlueNZ

    Next/previous switching a multiplexer

    You should be able to drive a pulse stretcher from the output of the receive optocoupler in the MIDI IN circuit. Power the pulse stretcher from the 5V rail in the accessory. You only need an optocoupler if you need to maintain isolation between the circuitry in the MIDI transmitter and the...
  20. KrisBlueNZ

    What is the purpose of this circuit board?

    As Dave said: The main component, that determines what the board does, is hidden under the black blob. It is a small piece of silicon that has been mounted directly onto the circuit board, connected to nearby tracks with tiny wires, and completely enclosed in a blob of black goop to protect it...
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