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  1. J

    find the answer

    You mean 5V? I don't think that is right for the capacitor once it is charged
  2. J

    Quick transformer question

    I wonder if you could take a 18V secondary with a center tap and connect one side to GND and then the center tap would be 9V and the other side be 18V. Though I have never tried it before. Seems reasonable
  3. J

    IGBT ignition coil driver

    Forget that, windows 7 has a snipping tool. Best thing since sliced bread, else there is always paint. Ctrl + Print screen and then Ctrl + P in paint, crop edit save and post.
  4. J

    MOSFET Help

    You will probably want a resistor to control the current, but if the current is limited too much the FET may never fully turn on due to the time it takes to charge the gate capacitance. Find out what the max output current is of the 555 and set your resistor to this value or slightly higher. If...
  5. J

    IGBT ignition coil driver

    You want a voltage follower or common collector circuit. Right now when the transistor is off the gate will be held high. http://en.wikipedia.org/wiki/Common_collector Notice how Vout is on the emitter side with the resistor connected between Vout and Gnd I don't think you will need the cap...
  6. J

    miniature pulse vibrator

    the 555 timer is a dip8 package. You could look up the measurements or check the 555 timer datahseet for them. As for a water activated switch, maybe you could use the waters lower resistance to detect when it enters the water. This would then simply be your switch. Not sure how effective it...
  7. J

    Help with voltage controlled switch

    I can't say I am surprised by your comments steve. Always a monkey wrench somewhere in the mess.
  8. J

    MOSFET Help

    I don't get what you mean by this. According to the datasheet... I thought this threshold voltage was the turn on voltage and turn off voltage. The source is connected to ground as duke pointed out. Maybe someone else can straighten it out.
  9. J

    find voltage across diode

    is this your homework again? I'll give you a hint, is the diode forward or reversed bias? Maybe you drew it wrong, maybe not.
  10. J

    comparator as a switch to 8051

    schematic? The lm339 has an open collector output. This will stop you from ever reaching Vcc.
  11. J

    Help with voltage controlled switch

    Now that I am looking at it, that symbol you posted in last schematic is for p-channel depletion mode mosfet. Enhancement mosfets have dashed lines if I recall correctly. Or is that what you meant? I am just now getting used to mosfets. Never really used them before edit...
  12. J

    Help with voltage controlled switch

    must be I am slightly confused, anyone care to explain this high side low side thing? I thought for a high side load the transistor has to source current(connected to the battery side) and a low side has to sink current(be connected to ground). Is that not true? also, why couldn't you have...
  13. J

    optocoupler?

    http://electronics-diy.com/electronic_schematic.php?id=1020 You are looking for a logic level mosfet. That will eliminate the need for a driver as long as you don't need fast switching. edit: added the fast switching part
  14. J

    optocoupler?

    why not a mosfet?
  15. J

    optocoupler?

    Not unless you need/want isolation.
  16. J

    How does this circuit work?

    You can delete it by editing it. Though, it may help someone else. By all means leave it if the information is valid. But don't expect the OP to see it.
  17. J

    How does this circuit work?

    I don't think it is gonna help much to answer a 2 year old thread. ;)
  18. J

    binary-coded decimal

    if you hold nine fingers up and start counting at zero, what do you end at?
  19. J

    binary-coded decimal

    1-9 == 0-8 It is still 9 bits. No matter how you look at it. Just because you start at zero doesn't mean you exclude zero.
  20. J

    binary-coded decimal

    are you for real? 1 0 1 1 1 0 1 1 1 | | | | | | | | | 1 2 3 4 5 6 7 8 9
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