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  1. KrisBlueNZ

    Help with frequency divider

    Yes, a CD4059 if you can find one (Digi-Key still have some) or for a smaller solution, a CD4024, but that will only give you division by powers of 2, i.e. 2, 4, 8, 16, 32, 64 etc, unless you mess around with the reset pin. You need to convert your incoming signal into a clean wave with steep...
  2. KrisBlueNZ

    Noob trying to replace android tablet battery

    The reason I asked is that removable batteries in mobile devices usually have at least three connections, because the battery assembly normally includes some circuitry. Some possible functions of this circuitry are: (a) monitor the battery temperature during charging to detect end-of-charge and...
  3. KrisBlueNZ

    Light measurement

    It will have a DC offset equal to half the positive supply voltage, i.e. +4.5V. He wants to feed this signal into an ADC with an input range of 0~5V. So even if the 9V supply was stable, he would still have to deal with a 90% offset and using only 10% of the range of the ADC. He hasn't even...
  4. KrisBlueNZ

    Light measurement

    Adam's circuit won't do what you want. Stick to your original circuit but change the op-amp. You will need to change the pin connections because the LM358 is a dual op-amp and the 741 is a single one.
  5. KrisBlueNZ

    Noob trying to replace android tablet battery

    Were there only two connections to the battery?
  6. KrisBlueNZ

    Light measurement

    Right. That will be a problem if you're using a 741. I don't know what you mean. Good. Use one half of an LM358 in your existing circuit. If the positive power supply is 5V then the op-amp's output will only go up to about 3~3.5V. If the positive supply is higher than about 7V you may need...
  7. KrisBlueNZ

    Strange voltage reading from AC adapter

    Hey, I like the meter! There's nothing wrong with them for most uses. When I was doing consumer repairs I used an analogue meter in preference to a digital meter most of the time. I still have a very nice old Hioki analogue meter. Just like Bob said. Don't worry that the meter indicated voltage...
  8. KrisBlueNZ

    Will it be safe power more than one LED with this circuit (555 timer,Highpower LED)

    If you build the second circuit from your first post, the LED brightness will drop when the supply voltage drops below about 12.5V. That circuit also has no protection against high supply voltages caused by spikes, surges, and load dump, which could damage or destroy the 555, the MOSFET, and the...
  9. KrisBlueNZ

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

    The peak inductor current is roughly equal to: IL(pk) = 2 × IOUT × VOUT / VIN. Do a worst-case calculation with minimum VIN and maximum IOUT and add at least 50% to the calculated peak current, and use that to specify your inductor.
  10. KrisBlueNZ

    Light measurement

    Hi there and welcome to Electronics Point. That circuit is a transresistance amplifier. It amplifies a current from the photodiode and converts it into a voltage at the output. You can't use the normal formulas for an inverting amplifier, since there is no input resistor. The 741 cannot...
  11. KrisBlueNZ

    Strange voltage reading from AC adapter

    What model is your voltmeter?
  12. KrisBlueNZ

    Transmit and receive parallel data through radio link

    In case you're still interested in a discrete solution, here's mine. It's designed around 74HC devices. Three ICs in the transmitter; four in the receiver. I don't have time to describe it in detail now and I haven't finished the timing diagram either. I'm going to be busy over the next few...
  13. KrisBlueNZ

    safety device on curves for automobiles

    I'm afraid this subject is not allowed at Electronics Point for safety reasons. Any device that is able to automatically apply the brakes in an automobile is potentially very dangerous and quite likely illegal. I am closing this thread.
  14. KrisBlueNZ

    Please help me identify this component

    Yes, and yes!
  15. KrisBlueNZ

    Starter Solenoid Switch

    It's possible and modern cars may even do it; I don't know. A contactor is more appropriate because of the extremely high currents and the extremely harsh electrical environment (switching noise, spikes caused by inductance, etc). The MOSFET would need a lot of protection components. The major...
  16. KrisBlueNZ

    Chicken Coop Door Opener

    Yes, the "limit switch" will be a Hall sensor. I don't know how the door is arranged so I don't know where you would mount it. The way that code is written, it expects the signal from the limit switch to be low when the door is open, and high when the door is closed. If you drive that pin...
  17. KrisBlueNZ

    Low voltage cutoff circuit

    A good choice for this application is the ICL7665. Three resistors set the switchover voltage and the hysteresis level. The output can drive the gate of a P-channel pass MOSFET directly. See the Intersil data sheet at http://www.intersil.com/content/dam/Intersil/documents/fn31/fn3182.pdf...
  18. KrisBlueNZ

    Clock generator

    There's a good general document that covers the standard single-gate Pierce oscillator that can be built using CMOS or 74HC gates at http://www.crystek.com/documents/appnotes/Pierce-GateIntroduction.pdf
  19. KrisBlueNZ

    [free energy] is there hidden power in plain sight?

    elfstrom7md, please don't post messages consisting of someone else's message, quoted, without adding any text yourself! When you see a message you want to reply to, and click Reply at the bottom of it, an edit window appears, with the original post quoted (with tags around it). Add your own...
  20. KrisBlueNZ

    Can I connect GNDs?

    How about using a single bridge rectifier feeding the resistor directly, then a series diode to the smoothing capacitor and the rest of the circuit. The series diode will prevent the resistor current from discharging the smoothing capacitor. There would only be one 0V rail.
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