3 power supply combo help

Discussion in 'The Projects Forum' started by minkey01, Nov 10, 2015.

  1. minkey01

    Thread Starter Member

    Jul 23, 2014
    171
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    Hi! Could someone help me with some power supply questions?

    Attached is the picture of what I am trying to do.

    My project has 3 separate power supplies. Power supply 1 is for a motor. Power supply 2 is for a tape head. Power supply 3 is a small wall wart to provide external power to the microcontroller. I want to put all 3 supplies in the same housing.

    1) Do I need to connect all 3 DC GNDs together? Power supply 2 came with the housing and already has its DC GND connected to the chassis. Right now the other new 2 are not connected to the chassis.

    2) My new control panel has jacks and pots on it. Should this panel be conductive and connected to the chassis or which GNDs? My jacks and pots are using AGND on the microcontroller. So maybe this panel should stay isolated from the chassis and other grounds?

    3) Power supply 1 has the three prongs to the AC outlet. The other power supplies only use two prongs to AC. Do I need to connect the AC GND on power supply 1 to the chassis?

    * Basically I just need some help with the overall grounding system of what you see in the picture. Thanks so much for the advice!!

    3 power supplies.jpg
     
    Last edited: Nov 10, 2015
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    How is the micro controlling the outputs, is it giving out 5v, or are you using relays, or opto couplers?

    I wouldn't connect the psus to ground, as this may introduce ground loops, and buzzing on the audio.
     
  3. minkey01

    Thread Starter Member

    Jul 23, 2014
    171
    0
    some micro controller outputs will trigger SSRs. other micro controller outputs will go directly into the motor. the motor inputs are also opto isolated. so all outputs on the microcontroller will be opto isolated. the inputs on the micro controller are not.

    which ground are you talking about? you wouldn't connect the psu's grounds to the chassis ground? would you connect all the psu's grounds to each other? what about the ac ground? anything to the chassis ground? sorry for so many questions.

    there are a lot of ground setup possibilities and im trying to figure out which one. thanks!
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Ok, i wouldn't common all the negative supplies, as they could interfere with each other, best to use opto-couplers for output switching, connect the Ac ground to the metal chassis as needed for protection against shock.
     
  5. minkey01

    Thread Starter Member

    Jul 23, 2014
    171
    0
    ok. great. so nothing needs to be connected even if all 3 psu are in the same chassis? the 3 psu can just be separate and float. only the ac earth connected to the chassis.

    that psu #2 is the original that came with the chassis. they have the 0V DC connected to the chassis. should I try to disconnect this?
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Leave it alone, where are the inputs to the micro from, push switches?
     
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