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Thread: The Bug is back

  1. #211
    Join Date: Nov 2014

    Location: Leicestershire

    Posts: 257
    I'm Mark.

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    Quote Originally Posted by Bksabath View Post
    Attachment 29071

    I am working on the soft start board

    whit 2 800 Va transformers the surge current at power up is far to hi to safely rate the fuses

    I am going to use 2 relays for each transformer the first one power the transformer trough a thermistor the second relay to bypass the thermistor

    Four delay on timers will take care of the sequence

    It has it's own supply from the mains whit a small block transformer
    Neat!

    Sent from my G8441 using Tapatalk

  2. #212
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 492
    I'm Sandro.

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    Thanks Mark

    I do not like the “blue” PCB version
    The Zenner supply is quite …all that said I have used the blue boards on 2 previous build and they are adequate
    Besides any PSU whit 300 VA or more need a soft start
    I have 2 X 800 VA traffos
    DSCF2676[1].jpg
    I am going to start whit same simple circuit for the on off signals
    The blue boards use 12 V relays that do need 2 times as much current than the 24 V
    The ones I am using are "solid" and have spare terminals for the Thermistors

    I am looking at the ULN 2003 supply can go up to 50 V and is an array of 7 Darlington’s Each output is capable of 500 mA
    Its das look quite interesting the 3 spare outputs can be used as on off and standby function
    I will start a simpler version of the timing circuit that closes the relays in sequence
    I need 150mS delay between RL1 and RL2 probably a longer time for RL3 to kick in and trigger RL4 after another 150Ms
    The function of RL1 and RL3 is to power on the transformers
    While RL 2 and 4 do the Thermistor by Pass
    There is also the possibility to Include an ARDUINO Daughter board
    This is going to be to far above my head but what about using the Arduino as speaker protection?
    Attached Images Attached Images

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