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Voltage stepper

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by wickedfun, Feb 20, 2008.

  1. wickedfun

    wickedfun New Member

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    Hi all,
    I am in need of help with a circuit I would like to build. I can build an electronic circuit no problems but design them I cant. What I am wanting to do is have a single push button switch that will have 4 different stages. I have a 12v battery, on the first push of the button I want to ramp up from 0 to 8vdc (+/- 2 second ramp time) , the second push of the button I would like to ramp from 8vdc to 10vdc (also a 2 second ramp) the third push will ramp from 10vdc to 12vdc (also 2 second ramp) on the forth push of the button I would like to switch the circuit off and reset. Should I push the button again I want to start all over.
    If anyone could give me some advice as to where I can start searching for help on this and what I should search for.

    Thanks in advance
    Sean
     
  2. Roff

    Roff Well-Known Member

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    Can you explain why you want this? Are you going to drive some sort of load (motor, lamp, etc.) with it?
     
  3. Diver300

    Diver300 Well-Known Member

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    What I suggest is this:-

    Find an adjustable voltage regulator that has a reference / feedback voltage to ground. These are usually 1.25 V to ground. LP2952 is one type.

    There are normally 2 resistors connected to the feedback point. One is to ground and one is to the output voltage. You need to have a third resistor connected between the feedback point and a control signal.

    The control signal would come from an output pin microcontroller. The microcontroller output will have a variable duty cycle, to control the voltage. There has to be a capacitor to smooth the duty cycle and make it a variable voltage.

    The pushbutton would go to a microcontroller input.

    You need R1, R2 = 10 k:eek:hm:
    R3 = 7.7 k:eek:hm:
    R4 = 48k:eek:hm:
    if you are using a voltage regulator with a 1.25V feedback.

    R5 can be just about anything.

    C1 should be about 100 :mu:F

    The pic program needs to remember what part of the cycle you are in, and it needs to produce a variable mark-space ratio. The bigger the mark-space ratio, the smaller the output voltage, but this circuit has the advantage that there is a linear relationship between mark-space ratio and voltage.
     

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  4. dave

    Dave New Member

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  5. wickedfun

    wickedfun New Member

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    this will be driving a 50w lamp.
     
  6. Hero999

    Hero999 Banned

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    Then use a PWM circuit to control the brightness rather than messing around with trying to vary the voltage.
     

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