power supply

Discussion in 'The Projects Forum' started by akurayo, Apr 28, 2011.

  1. akurayo

    Thread Starter New Member

    Apr 28, 2011
    I have a project using 30v power supply.My objectives in this project are to divide those 30v power into 2 section,whereas section A it will drop till 24v and section B drop till 1v.
    But I have a problem about the measurement for resistor.I need to use the suitable amount of resistor to drop the voltage for those two section where in the same time I must make sure the current flow in this circuit was not more than 1A.
    I hope somebody can help me to choose which resistance I need to use or did I need to add another component to prevent from burn the resistor.

  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    What do you need 24V and 1V for, and how much current is required in each case? Does the current vary?

    Depending on what is needed, it may or may not be possible to do this simply with resistors.
  3. wayneh


    Sep 9, 2010
    If the only current flowing is through your divider, then you can add another section so that 24 + 1 + x = 30v. Of course x=5v.

    Use Ohm's law to calculate the total resistance you want. Pick a current, say 0.2A. You need to drop 30v across a series of resistors: V = IR and 30 = 0.2R. So R = 150Ω. You can apply this same approach to each segment:
    30 = 0.2•150
    24 = 0.2•120
    5 = 0.2•25
    1 = 0.2•5

    Note that this falls apart if a significant current (>10% of the divider current) is going somewhere else out of the divider.
  4. SgtWookie


    Jul 17, 2007
    If you are planning on supplying voltage to (a) load(s) where the current through the load(s) may vary, you will need to use voltage regulators instead of fixed resistors, or your voltage regulation across your load will be very poor.