replace batteries with transformer

Discussion in 'The Projects Forum' started by walterholt, Oct 14, 2011.

  1. walterholt

    Thread Starter New Member

    Oct 14, 2011
    2
    0
    I would like to stop using batteries in my new Radio Shack digital AM/FM pocket radio - Cat. #12-587.
    The radio is powered by 3 AAA batteries.

    I am thinking I should be able to buy a simple 120volt to 4.5 volt transformer and hard wire it to the contacts of the battery holder, that is, just solder the 4.5v output leads to the plus and minus ends of the battery holder contacts.
    With this set up I could listen 24/7 without replacing the batteries every 3 or 4 days.

    Can this be done? What current output should the transformer provide at 4.5 volts?

    I have a limited knowledge of circuitry and no understanding of resistors, diodes, capacitors etc. I did however manage to sucessfully build several Heath Kit items back in the day.............

    Any suggestions will be appreciated.
    Walter
     
  2. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Likely a 5 volt DC wall wart would do the trick. We can't devine the actual current from here, but, being battery operated, 200ma should work. What the H. Splurge and buy 500 ma or a whole amp of current.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A battery produces DC. A transformer produces AC. AC will probably blow up your radio.
    A 4.5V AC transformer has a peak voltage of 6.4V which is reduced to 4.8VDC by a rectifier bridge and filter capacitor. The voltage will be much higher with less than the rated current and might be high enough to blow up the radio.
     
  4. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Good points, AG. The problem would be in finding a REGULATED 4.5V wall wart...but I suspect 5 volts would work. Possibly put an 1N4001 diode in series with the 5 volts to knock it down to 4.3V.
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    A cell phone wall charger rated at 5.0V - 5.2V with a 1N4001 diode in series would work great. Be sure the polarity is correct.

    Here's the adapter for you and no diode needed!
    4.7-VDC-850MA-POWER-SUPPLY
     
    #12 likes this.
  6. walterholt

    Thread Starter New Member

    Oct 14, 2011
    2
    0
    Thank you all for your knowledgeable suggestions. Special thanks to Audioguru for your warning and to iONic for actually locating the perfect power supply which I have already ordered.
    Walter
     
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