Basic help with LCDs

Discussion in 'Embedded Systems and Microcontrollers' started by darrough, Nov 15, 2015.

  1. darrough

    Thread Starter Member

    Jan 18, 2015
    86
    19
    I am trying to connect a LCD to a PIC MCU.

    For power, I am using 4 AA cells with a 7805. Disconnected from the circuit, the DMM shows 5.7 volts from the 7805. When I measure at the LCDs power input, the DMM shows 5.4 volts. The LCD power input is wired directly to the 7805. Should I be concerned about this? Does this mean that the 7805/batteries are unable to supply the required current?

    When I measure current going in to the LCD the DMM shows 0.4 maximum. The datasheet for the LCD says that it uses "typically" 2 milliamp. Does this further my hypothesis that the batteries cannot supply the required current?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,507
    2,367
    The minimum input for a 7805 is around 7.5vdc.
    Max.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Are you using new AA's?
    The dropout voltage for a 7805 is 2V, so to get 5.0V at the output, you will need to start with 7V or higher. Look at LDO regulators...
     
  4. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
    2,831
    89
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