Mains Adaptor Problem

Discussion in 'General Electronics Chat' started by ardali, Nov 5, 2014.

  1. ardali

    Thread Starter New Member

    Dec 4, 2012
    I have problems with a circuit involving MC14052 multiplexer chips. I decided to test the chips on abreadboard. They are OK with a 12 volt battery as source. But with a 12 volt adaptor as source I read aprox. 3 volts at all input/output pins regardless of the inhibit pin is 1 or 0. I tried several adaptors with a 10 uf capasitor across the leads.
    Any ideas ?
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    that is the float (not connected ) level. have you tried connecting the inputs to ground?
  3. ardali

    Thread Starter New Member

    Dec 4, 2012
    Both input pins earthed and I/A/B pins are 1/0/0 respectively I read 3 volts at all output pins. When inhibit pin is changed to 0 (A and B still 0,0 : 0x and 0y pins ON ) I read 0 volts on ON pins 1 and12 as expected but still 2.7 volts on all other 6 output pins.
    I would like to repeat that with a 12 volt battery as source all readings are what they should be.
  4. Motardo


    Sep 21, 2011
    Some cheap wall adapters are nothing more than a transformer and a diode. There is no filtering and no voltage regulation. So a 12V adapter might generate half wave rectified 18V pulses instead of smooth DC. Can you check the output with an oscilloscope?