NiCad Restorer Question

Discussion in 'General Electronics Chat' started by JoeyElectronicsGuy, Mar 8, 2016.

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  1. JoeyElectronicsGuy

    Thread Starter New Member

    Feb 5, 2016
    Mod edit: snipped image of Transformerless PSU
    Hi all, I'm trying to build this and was wondering two questions:

    1) Which way does the positive end of the 2 capacitors face in the Diagram? Towards the alligator clips or towards the AC line cord. Physically. They are not marked.

    2) Also, do you think the push button switch momentary or not?

    3) The neon light doesnt work in the test one I'm building. But I have a 105v to 125 v ac/dc lamp. Maybe I should have bought one with a lower voltage rating. What do you think?

    4) What should the output at the alligator clips be?

    5) I have the diode but was wondering about the polarity of the caps. Does it make a difference which way they are connected?

    Thank you. Any help with any of the questions above would be very much appreciated.
    Last edited by a moderator: Mar 20, 2016
  2. ian field

    Distinguished Member

    Oct 27, 2012
    The best way to revive Ni-Cd cells is with pulses.

    One of my designs was a modified ATX PSU, a charge coupled voltage double which is inherently current limiting was fed from a secondary on the chopper transformer.

    The rectifiers were deliberately mis-matched - the shunt diode in the doubler was Shottky-barrier to minimise negative pulse amplitude, the pass rectifier was just a fast recovery silicon type so the reverse recovery spike caused a very narrow charge current reversal.

    My charger was used exclusively for 4.8V packs, so the current draw from the 5V rail that's needed to keep the PSU running, provided a steady charge bias through a current limiting resistor.

    More recently I've had a project published in Elektor magazine. Its a basic linear PSU design, but a zero crossing detector pulses a MOSFET to shunt the battery between rectified half cycles. The magic is in the blocking diodes that prevent the battery voltage interfering with the zero crossing detector, and preventing MOSFET activation in a power outage.

    Not recommended for Ni-Mh, except for short treatment sessions on cells that have got lazy.
    Last edited by a moderator: Mar 20, 2016
  3. SLK001

    Active Member

    Nov 29, 2011
    The positive end of the cap connects to the cathode side of the diode.
    JoeyElectronicsGuy likes this.
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    This has been here before its a TRANSFORMERLESS PSU!!
  5. ScottWang


    Aug 23, 2012
    The owners of All About Circuits has elected not to host discussions of transformerless threads.

    Transformerless powersupplies are not allowed over here.
    See point 6 of the user agreement:

    If you wish to change to using the transformer and continuing to discuss then please press report button, when our mods through the discussion, if we decide to reopen it then we will reopen.

    Good luck.
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