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Convert DC power to AC power

Discussion in 'General Electronics Discussion' started by William Loos, Dec 1, 2010.

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  1. William Loos

    William Loos

    Dec 1, 2010
    I would like to rewire my exercise bike from DC (4 each D batteries, situated as two rows of two batteries each in the battery compartment), to AC power, using an AC power adapter. The bike has 3 wires going from the battery compartment to the printed wiring card. The red wire goes from the positive battery connection to the VDD terminal connection on the board; the black wire from the negative battery connection to the GND connection on the board and the yellow wire from a second positive battery connection to the VCC terminal connection on the board. How do I properly splice the positive and negative wires from the AC power adapter to the three wires leading from the board to the battery compartment? I intended to connect one adapter wire to the black; and the other adapter wire to the red, but upon opening the bike and seeing the third yellow wire, I'm unsure what to do. Many Thanks.
  2. LTX71CM


    May 23, 2010
    If you do exactly as described you will destroy the circuit in your exercise bike. You can power the circuit from household mains with a power adapter but you need a regulated AC to DC adapter. It sounds like the the yellow wire is connected in the middle of the string of batteries. Is that correct? You would need a six volt and a three volt adapter or a six volt adapter and a 3v external regulator just for that tap or if you're lucky a voltage divider. Really just depends on what the yellow wire powers and how critical it is. Can you post pics? That would help.
  3. William Loos

    William Loos

    Dec 1, 2010
    More Info Convert AC to DC Power

    I planned to use a 6V power adapter that has 2amp output (Enercell 273-333). This URL gives info on the power adapter:$30.00+and+up&filterName=Price

    View the pictures of the front & back of the battery compartment and of the pwc showing the 3 wires going to the battery compartment at:

    The yellow wire is connected in the middle of the string of batteries. Further guidance is much appreciated.
    Last edited by a moderator: Dec 2, 2010
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    No, that power supply on its own isn't going to work.

    You need a power supply that gives you +/- 3V, or 3V, and 6V with a common earth (effectively the same for your purposes.

    Radio Shack gives no technical information, but I suspect that this device is a multi-tapped transformer with rectifier and filter. That means the voltages off load will be significantly higher than rated (which may damage your equipment, since it is designed for battery operation).

    For what it is, it is very expensive, but that's Radio Shack for you.

    I would get 2 LM317's and use them to create a 6V and a 3V rail from this power supply set at maybe 8 volts. I suggest LM317's because both regulator circuits will be very similar other than for the resistors used to set the voltage.

    Here is a circuit and a calculator. Note that I would recommend you use R1 = 120 ohms. You need 2 of these, one for 6V and one for 3V.

    The common ground connection goes to black, the 3V to yellow, and the 6V to red.
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