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ac curent detector

Discussion in 'Electronic Basics' started by burosky, Oct 8, 2005.

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  1. burosky

    burosky Guest

    I'm just wondering if the LM1458 of ac current detector from Bowden's
    Hobby Circuit doesn't need any supply at all. Since its pin # 8 & 4 are
    not stated on the schematic diagram. Will it be possible to precisely
    set any desired current setting to activate relay (i.e 4 amps). What's
    the 1st op-amp used? Is it TL061/62? With regards to the pick-up coil,
    are there any wounding procedures? Will it be right if I just wound it
    continuously w/o putting anything between layers?

    Hope you can help me with this.
     
  2. Jamie

    Jamie Guest

    alot of prints do not show the Rail supply lines to the
    IC's
    they assume you should know better.!
     
  3. Rich Grise

    Rich Grise Guest

    We would be a lot more able to help you if you'd post a link to the
    circuit you're trying to build. The LM1458
    http://www.fairchildsemi.com/ds/LM/LM1458.pdf
    definitely needs a power supply. The first op-amp used is probably
    one of the sections of the LM1458, and as far as the pickup coil,
    it depends on what you're trying to do.

    What do you have on this thing so far?

    Thanks,
    Rich
     
  4. w2aew

    w2aew Guest

  5. Chris

    Chris Guest

    As mentioned in the other posts, the LM1458 is an 8-pin dual op amp.
    Even though the drawing shows two separate op amps, it's all one IC,
    and all eight pin connections are there.

    As mentioned at the bottom of the circuit description

    http://ourworld.compuserve.com/homepages/Bill_Bowden/page8.htm#aclatch.gif

    the circuit is set to have the second op amp (which is used as a
    comparator) turn on the transistor with a current of about 1/4 amp AC.
    Also, as he mentions in the writeup, you can increase the sensitivity
    by increasing the number of turns. You can also decrease the
    sensitivity by decreasing the number of turns. They're not directly
    proportional, though.

    You should hook up a line cord to 4 ea. 100W bulbs, and reduce the
    number of turns until it just doesn't turn on. You will then have
    fairly reliable turn on at about 4 amps (or 480 watts at 120VAC). I
    would guess something around half the number of turns on the U-bolt
    would be a good start.

    Magnet wire has a very thin enamel insulation, which is easily
    scratched. It isn't necessary to provide insulation between layers.
    However, it is very necessary to avoid winding over the threads of the
    U-bolt. The sharp edges of the threads will short out the insulation,
    and ruin your work. Make sure you use an iron U-bolt.

    For a "real world" current detector, tape one end of a 6' zip cord to
    the U-bolt, then solder the ends of the wound magnet wire to the
    dressed leads of the zip cord. Also, be sure to at least tape the ends
    of the magnet wire down. Once you've got it working, a layer of tape
    all around might not be a bad idea. Copper wire of this diameter will
    break out of spite if you even look at it wrong. And for hobbyist
    stuff like this, electrical tape can be your friend.

    Mr. Bowden's circuit is versatile, and can also be used to give a
    fairly accurate reading of peak AC current (by measuring the voltage
    across the second 10uF cap).

    Good luck. Feel free to post again if you have any other questions or
    problems, or to let us know how it works.

    Chris
     
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