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

 

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

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Ron

 

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 khm:
R3 = 7.7 khm:
R4 = 48khm:
if you are using a voltage regulator with a 1.25V feedback.

R5 can be just about anything.

C1 should be about 100 µF

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.

Attached Images

volt1.gif (4.6 KB, 11 views)

 

this will be driving a 50w lamp.

 

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

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