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  • #6120
    Solideo
    Participant

    So I was right to think of oversight ,that I went crazy this morning.

    #6545
    Solideo
    Participant

    E’ a problem arose, l’ atx that i can use does not have -5V, so I was thinking of a 7660a which is a dc / dc converter that with only 2 10uF capacitors I would have -5V from + 5V, it could be a problem?

    #6550
    Amilcare
    Keymaster

    It is more than good since it only serves to drive the gate of the mosfet. The current at the gate is negligible

    #6575
    Solideo
    Participant

    I'm back,
    unfortunately it does not limit the current, provided he hasn't made any mistakes.
    So I mounted it on bread and used an active load as a load, set to absorb about 1A , at this point acting on the potentiometer nothing changes, that is, the load always continues to absorb 1A.
    At this point I tried to measure the voltage on the pin 1 of the lm358 and mass, e và da -1.7V a +10V, according to the position of the potentiometer, all on one side or the other.
    There is some evidence that I could make or change?
    Thanks so much.

    P.S.
    I made the connections all over again.

    • This reply was modified 3 years, 2 months ago by Solideo.
    • This reply was modified 3 years, 2 months ago by Solideo.
    #6583
    Amilcare
    Keymaster

    Try to see if increasing the absorbed current the output voltage drops, this circuit is essentially a constant current generator, eso lowers the output voltage when the current exceeds a certain level in order to stabilize the current.
    I advise you to test with a resistance, the active load varies its characteristics to always have that circulating current and risks that the two circuits compensate each other to stabilize the current.

    #6592
    Solideo
    Participant

    Tested with a resistance of 2 hom, about 2.4A of current but regulates only 0.1A.

    #6598
    Solideo
    Participant

    Since it must ultimately be a constant current generator, I thought of this:

    ++++ Loading image FidoCad ++++
    see source fidocadj Zoom fidocad

    It should limit from 0.1A to about 1.5A.
    The resistance should dissipate P = ( i * i ) * r = ( 1.5 * 1.5 ) * 1 = 2.25 Watt
    while the transistor which has an rds 0.16 ohm P = ( 1.5 * 1.5 ) * 0.16 = 0.36 Watt
    always if I'm not wrong.
    I saw that they are added 2 0.1u capacitors between the inverting pin and ground and the non-inverting pin and ground, what are they for?

    #6600
    Amilcare
    Keymaster

    Yes, but it should not be on the 5V line?

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