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  1. BobK

    How hot is too hot for a phone?

    Sorry, my education did not include enough to guess at this. I don't think anyone can give you a reasonable answer to this. For one thing, not all parts of the phone will be at the same temperature. It is quite possible that you could comfortably hold the phone in your hand, while one...
  2. BobK

    How to connect a windshield wiper motor to a battery

    The light blinking probably indicates that the power supply is in current limiting mode. If it is adjustable, turn the current limit all the way up. Bob
  3. BobK

    How hot is too hot for a phone?

    When it starts melting it is too hot! But, seriously, your question is ambiguous on several levels. Do you mean the highest ambient temperature at which it can be operated, or how hot the phone itself can get before it is damaged, or even what temperature will damage the phone even if it is...
  4. BobK

    12V down to 7.4V (Buck converter?)

    You do not give a device 5A. You give it a voltage, it will take as many amps as it needs at that voltage. This is why a night light does not explode when you plug it into an outlet that can provide 15A. Bob
  5. BobK

    Learning Unijuctions

    I can only say check all the connections and especially the pinout on the UJT. Bob
  6. BobK

    12V down to 7.4V (Buck converter?)

    Here is what the link says: Whatever that means. Another add for what looks like the same board says 1.8A continuous, 3A max. The datasheet for the chip says 3A continuous, but it probably depends on the thermal design. Bob
  7. BobK

    Salty ground voltage

    How about telling what you are hoping ot accomplish be sticking two rods of different metals into the ground. Bob
  8. BobK

    12V down to 7.4V (Buck converter?)

    Also, you have not told us how much current the monitor requires. The board seems to have a limit of 1.8A, and, if it is really as efficient as they say, it should be able to handle that current without a heat sink. Bob
  9. BobK

    12V down to 7.4V (Buck converter?)

    One of the outs should have been lablelled +. If you simply guessed, you are lucky you did not destroy your camera or monitor. You should check the polarity with a meter to see which is + and which is -. Can you post a link to fleaBay offering for this board? Bob
  10. BobK

    12V down to 7.4V (Buck converter?)

    The buck converter should not run significantly hotter whether the input is 9V or 12V. Some of these boards state a maximum current, but require a heat sink (not included) to reach that max. Check with the seller. Bob
  11. BobK

    The collapse of a magnetic field

    Why are you rejecting the boost mode converter? The fact that current comes from the battery and the inductor just increases the voltage available to charge the capacitor. And it does not have the possibly annoying property of inverting the voltage. Bob
  12. BobK

    Maximum socket outlets

    Well, as soon as you have more than 1 typical socket and breaker you can overload it, so the true answer is probably 1. But in practice, I know more are allowed by code. You would have to check the electrical codes for your location. Bob
  13. BobK

    Capacitor Protection Boards- How do they work?

    It's a 2SD1804 NPN power transistor. http://pdf.datasheetcatalog.com/datasheet/sanyo/ds_pdf_e/2SD1804.pdf Bob
  14. BobK

    looking for rotary switch or pantometer that works via USB HID class

    A mouse wheel? Bob
  15. BobK

    SCR latching trouble

    If the buzzer is of the electromechanical type (essentially a relay that disconnects itself when activated) then it will break the circuit for each click, turning off the SCR. Haralds suggestion should fix it. Bob
  16. BobK

    Just need a few suggestions

    This would be quite a challnge. Based on the size of state of the art devices today, maybe inpossible. A 35 year power source is not something you see every day. It might exist, but I have never seen such a thing. It would have to use cellular phone technology and gps, but will it even be...
  17. BobK

    Monostable multivibrator

    With the supply at 9V, yes, you would need two level translators. I was thinking 5V supplies. Bob
  18. BobK

    Monostable multivibrator

    d. Microcontroller and 3 MOSFETs (half bridge and level translator) Bob
  19. BobK

    A simple one with LED strip

    LED strips typically have the resistors built in and are designed to run off a fixed voltage. All you need is a power supply of the correct voltage and a higher current rating than the strip needs. Bob
  20. BobK

    Passive low-pass filter

    First, you need to show us a circuit. We cannot assume what you did. If you are using a 1K resistor in series with the speaker, or course it will reduce the volume to nothing. With a 10 ohm, it will still reduce it to less than half. The speaker itself would be the R in a first order RC...
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