I made a +-2.5 Dual supply. Although, grounds are different. There is an issue!

Discussion in 'The Projects Forum' started by demerda2, Jan 21, 2016.

  1. demerda2

    Thread Starter New Member

    Jan 21, 2016
    1
    0
    So, I have this ADS that I am interfacing with a microcontrollter called C2000.
    ADS works with a dual supply (+2.5 and -2.5), and C2000 with a 5V.

    I made the following schematics and I can get a +-2.5V to supply the ADS1299.

    I use the C2000 to interface with ADS1299, which means that both grounds should be tied together.

    The whole system consumes around 50mA.

    And according to this schematic that i made, this isn't possible because the references are different.

    [​IMG]

    At first I thought about making separate rails:

    [​IMG]

    This is definitely gonna work, both devices could share the same ground. Although, the parts I would need for this can't be found easily in my country, and I would need to buy most of them from somewhere else which would take time and money.

    So, going back to my first schematic. Instead of putting the c2000 before, I would put it after the ampop. But I would have to use a battery to bring up the voltage to 5V (I have a 2.4V battery so it would work) Something like this.

    [​IMG]


    Or maybe a different approach. Back to my 1st schematic, what if I make an unbalanced voltage divider?

    [​IMG]

    One last idea would be that I could use two 9V battery and use LM7805 to get 5V, followed by LM317 to get 2.5V and same thing to get the - 2.5V. But I don't know if that would be a good approach, even though I don't have to make it work for a long time straight. Just 10 minutes would do.

    Any suggestions??
    Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    I would go with your last approach using two batteries, one for the positive voltages and one for the negative.
    Otherwise it's difficult to get 5V and ±2.5V from a single battery without using a switching regulator.
     
  3. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    5,001
    745
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