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  1. KrisBlueNZ

    Dark activated light

    Yes, you should have a decoupling capacitor. All logic ICs should have one across their power supply pins. No, you don't need current limiting anywhere, but you might want to put a 1k resistor in series with the LDR to prevent possible damage in unusual circumstances. I'm glad to hear that it...
  2. KrisBlueNZ

    Google+ group?

    No. What would we want it for? BTW I like your sig :-)
  3. KrisBlueNZ

    Balancing charging of sixteen LiFePO4 cells

    Ok Bruce, I've merged your new thread into your existing thread on the topic of balancing these sixteen cells, and given it a useful name. I have no experience with battery balancing. Other Electronics Point folks do, and I hope they can offer some advice. Your requirements seem to be unusual...
  4. KrisBlueNZ

    Need help with analogue question

    That's a good explanation. And you showed your calculations for the high and low periods of the square wave based on a 1 Hz frequency?
  5. KrisBlueNZ

    Dark activated light

    That circuit won't work either. There are a number of errors. These errors would become clearer if you arranged the diagram the way I described. That is, with the negative rail along the bottom and the positive rail along the top. 1. You still have two batteries. There is no reason for this...
  6. KrisBlueNZ

    Balancing charging of sixteen LiFePO4 cells

    OK, the description is pretty clear: "Upper and lower limit alarm output signal is high level normally, if exceed the set value is low level." The HV and LV outputs are both high (+3.3V I think, relative to the circuit's 0V rail) if the voltage is within range. If the voltage goes out of range...
  7. KrisBlueNZ

    Dark activated light

    Good :-)
  8. KrisBlueNZ

    Total current drawn by the circuit???

    You're welcome :-) You can click "Like" at the bottom of my post to thank me formally.
  9. KrisBlueNZ

    Balancing charging of sixteen LiFePO4 cells

    It sounds like there are two separate relays which are both normally energised, so their contacts are normally closed. When an undervoltage or overvoltage occurs, the corresponding relay de-energises, i.e. its contact opens. This is called a "fail safe" type of alarm, because the alarm...
  10. KrisBlueNZ

    Help requested for a circuit design

    Your circuit is drawn upside down. It's normal to draw the 0V rail across the bottom. There is no need for the 2k2 base resistor. You can get the behaviour you want by connecting a diode with its cathode to the negative side of the capacitor and its anode connected to the 0V rail. Depending...
  11. KrisBlueNZ

    Really small motors

    I'd imagine electromagnets (solenoids) would be the way to do. Also you might get some ideas if you dismantle the printhead from an old dot matrix printer (if you can find one - try a technology museum :-)
  12. KrisBlueNZ

    SanDisk

    I have a micro SD to standard SD adapter as well, with a sliding "switch" that covers the write protect notch when slid forward. But the switch is so easy to move that when I slide it to the "write enable" position and insert the adapter into my laptop's reader, the switch slides into the "write...
  13. KrisBlueNZ

    Total current drawn by the circuit???

    This sounds like a homework question so I've moved it to the homework help forum. In the second circuit, do you need to work out the total current drawn from the power source at the left side? The first resistor, marked L1 (should be marked R1), has a known voltage across it, and a known...
  14. KrisBlueNZ

    SanDisk

    From https://en.wikipedia.org/wiki/Secure_Digital
  15. KrisBlueNZ

    Troublesome powersupply

    Same here. This design had it kind of backwards - the schematic has circuit references but no component values (should have both), and the PCB overlay has component values but no circuit references (should have references only)!
  16. KrisBlueNZ

    Troublesome powersupply

    Thanks Adam... the schematic was in the PDF linked in the first post; I just added the values.
  17. KrisBlueNZ

    Dark activated light

    Yes, a KIA358P is a second-source of an LM358 and will be just as useless in that circuit.
  18. KrisBlueNZ

    Troublesome powersupply

    Here's the schematic with component values added. IMO it's a pretty horrible design. Many other linear regulators would be better - several from the first page of https://www.google.com/search?q=variable+adjustable+linear+regulator+schematic&tbm=isch Digikey have a good selection of...
  19. KrisBlueNZ

    Why does my op amp sink/source current?

    I HATE it when people say this kind of thing. "Please, strangers, help me fix my circuit... But some of the specifics of the schematic are out-of-date, I'm only going to tell you about the things that I think are important because I know what's important and what isn't (even though I realise...
  20. KrisBlueNZ

    Why does my op amp sink/source current?

    Some random thoughts: There are two clear paths from LED- to 0V (i.e. in parallel with the MOSFET) in the current monitoring op-amp circuit: R6+R4 and R7+R5. You can sense the LED current by connecting your shunt between the MOSFET source and 0V. This voltage drop will be referenced to 0V. You...
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