HELLO,

HELLO I NEED A CIRCUIT THAT WILL RAMP FROM 0 TO 12vdc IN 1/2 SECOND THEN RAMP DOWN FROM 12VDC TO 0 IN 1/2 SECOND the load is .5 amp, (Voltage Wabbler) This circuit does not need to be precise, some adjustment for the time using a trimmer pot would be nice. Basically it would be like turning a potentiometer up and down over a 1 second period, This circuit would be turned on by a 555 timer and would free run as long as the timer signal output is on.

Any help is appreciated

Randallman

 

Hello. Glad you know what a 555 is.

The way to get a good ramp is to make a constant current supply fill a capacitor. What you're going to need is 2 constant current supplies connected to a 555 timer. One to fill the capacitor and one to empty it. The usual 555 circuits already have a kinda ramp, but it's an exponential because it's a constant resistance into a capacitor. The output of the ramping 555 will have to use a power transistor to supply the current.

There's a clue. I'm too lazy to design it for you. Take a shot and show us what level of understanding you have. Then the conversation can progress.

 

If it needs to be linear (as opposed the to the 555 ramp) I've done some experiments one that vane.

http://forum.allaboutcircuits.com/showthread.php?t=12405