# Using a pulse to trigger a polarity shift?

#### Mr_Me_II

Mar 8, 2010
2
Hello, I need to build a circuit for a friend...and I'm a little lost.
I need to generate a DC output of about 6 volts, and have it alternate once every 11 minutes. (Out1 = +5 Out2 = G ----11 Minutes----> Out1 = G Out2 = +5 ------repeat----->)

Trying to figure out how to achieve this...Maybe a +6v regulator and -6v regulator, have it switch between the two when a pulse from a timer is given? The actual switching is the only problem. And it needs to be automatic, I'm not going to throw a switch manually every 11 minutes

As for the timer...11 minutes, odd yes...I have a few 555/556 timers and am familiar with those...never used one for more than a few second delay though. How could I best achieve one pulse every 11 minutes, without the use of a PIC?

Suggestions would be appreciated

#### Mr_Me_II

Mar 8, 2010
2
Also as for the timer, 11 minutes is the goal but if it's going to have to be 11:03 or 10:54 that's fine...just as close to 11 minutes as possible while still keeping it fairly simple - device is to be pretty small when completed (aiming to fit it in a 2"x2" board, double sided if needed...)

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
What current is required? For low current (say a few mA) you can use logic gates. A very slow oscillator, followed by a couple of inverters (an odd number (1) for one output) and and even number (2) for the other output.

You could build the entire thing from a single CMOS hex Schmitt trigger package, a resistor and a capacitor. The issue would be temperature stability, and I wouldn't vouch for better than 5% (+/- 5 seconds -- ish).

If you want higher current, then you could use an H bridge (essentially 2 x a pair of transistors to switch either supply rail to a common point).

For more accuracy you could use a more stable oscillator and maybe a divider.

A really trivial option is to use a PIC (or a PICAXE). You could get the entire thing done in a single 8 pin SMD package -- it would all fit in a 0.5 inch by 0.5 inch board!

Replies
47
Views
4K
Replies
1
Views
919
Replies
3
Views
826
Replies
1
Views
2K
Replies
0
Views
5K