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  1. KJ6EAD

    does a 9V battery have a current limit?

    If you'll take a look at this, I think you can answer your own question. http://www.powerstream.com/9V-Alkaline-tests.htm If you recalculated your current limiting resistor for a 6V supply voltage, you might have decent output for a few minutes.
  2. KJ6EAD

    Can you help me find these parts?

    If you use a magnifier to look at all surfaces of the connector bodies you may find a manufacturer logo and/or part or series numbers. You will have to look under the flexible strain relief on the round connector.
  3. KJ6EAD

    Starting out in Electronics

    I don't like any of those. Make up your own list based on projects you want to build or experiments you want to try. None of those kits have a full E12 series of resistor values which you'll eventually need and you can get now to save on overlap later. Try this resistor kit. It has 61 values...
  4. KJ6EAD

    Maxitronix Electronics Lab 300 in 1, BROKE ON THE FIRST DAY??

    If you connected any of the LEDs to the power in reverse polarity, that would destroy them without flashing. They can only handle 5 volts or so in reverse. They shouldn't be difficult to replace and they certainly don't cost much.
  5. KJ6EAD

    Need help with going from 6V to 5V

    I don't believe it's that high. You need to measure it, not read the supply capacity labels. If it really is that high then carry a small backpack 12V battery and use two or three of those 1A USB buck converters as suggested unless you can find one rated for 2A. No, there isn't. Well, there...
  6. KJ6EAD

    unknown formula

    It's a version of the mutual inductance formula arranged to solve for the coupling coefficient. M is the mutual inductance; k is the coupling coefficient (0-1).
  7. KJ6EAD

    dunk tank

    I can think of at least a few reasons why you might want to electronically control a dunk tank. It would allow the difficulty level to be adjusted by changing the size of the target or it's sensitivity. It could be for a prank where little kids are successful while professional baseball pitchers...
  8. KJ6EAD

    Need help with going from 6V to 5V

    The single diode trick is a good one. It would be useful to know how much current the circuits actually draw in use; obviously less than 1.5A but how much less?
  9. KJ6EAD

    Quest smoke alarm randomly chirping

    They do that when they're old (weak Americium slug), dirty (partially blocked optical sensor path), underpowered or defective; or maybe your house is only slightly on fire. :eek: :D I've seen that symptom on ones where a single strand of spiderweb was in the optics or a little dust or soot.
  10. KJ6EAD

    dunk tank

    An electric strike is cheaper than a magnet and probably uses less power. I'm not sure about their ability to repeatedly open under load though. If your cantilever sketch is accurate, you're applying more load to the latch than the weight of the person. Resetting is as easy as closing a door. :p...
  11. KJ6EAD

    Project: The Star Trek Room

    If you installed a track or monorail lighting system and powered it with 12VDC you could use it as a mechanical suspension system for the models with one or two connections to the track and use individual regulators on each model/kit to reduce the voltage as necessary. It would be relatively...
  12. KJ6EAD

    Help with a toy

    Maybe these will fit or you can adapt them: http://www.keyelco.com/products/specs/spec47d.asp.
  13. KJ6EAD

    Complete N00b needs some advice

    Thanks for the follow up. It's always nice to know when projects that we participate in have a good result.
  14. KJ6EAD

    556 Timer project

    You can make a sequencer using a 555 and a 4017 decade counter.
  15. KJ6EAD

    What rpm must a 24v dc generator turn to produce 24v?

    If you have a multimeter with the ability to measure frequency, you can rig a small magnet on the shaft and use a small inductor to measure the rotations per second then multiply by 60 to get RPM.
  16. KJ6EAD

    Electronic Siren problem

    He probably had a diode or capacitor in backward and is too embarassed to admit it. :p
  17. KJ6EAD

    Complete N00b needs some advice

    The trick is to cut most of the way through the insulation all the way around then break away the remaining material so there's no chance of scoring the conductor(s).
  18. KJ6EAD

    100 ohm Resistor vs. 86 ohm resistor

    I reran your calculation. The optimal nonstandard value is 70Ω. The next higher standard value is given by the calculator. http://www.logwell.com/tech/components/resistor_values.html
  19. KJ6EAD

    Mute button

    Arbitrarily numbering the leads from top to bottom for each channel (left and right), the connections are probably L1-L2 to unmute channel L, R1-R2 to unmute channel R, L2-L3 to mute channel L and R2-R3 to mute channel R. Test with a shorting jumper or a pair of metal tweezers.
  20. KJ6EAD

    Help w/ Looping a Rec Module

    There are only two switch contacts formed on the circuit board as interlaced traces. The conductive rubber pad on the chicklet key shorts the two switch contacts.
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