I need very small timer 3min. on 10min. off nothing fancy.

 

Done.

 

I need very small timer 3min. on 10min. off nothing fancy.

No... What you need is to be more detailed with your question so that nothing is left up to "guessing"..

cycle repetition?
what are you even timing? or intending to add timing functions too..(voltage/current,etc..)

A timer for a 1000HP motor is quite a bit different than a timer for a single 20mA LED..

 

Here is a timer that will give upto 3.5 min on and upto 16 mins off using a CD4093 chip, Vr1 sets the on time, Vr2 set the off time.

 

A timer for a 1000HP motor is quite a bit different than a timer for a single 20mA LED..

What? so I cant use my 555 for my 100hp motor design?? lol

 

Are you killing cockroaches? Best way to deal with them is to first vacuum all you see, and then put out poisoned cockroach food and traps. Don't forget to take out the vacuum bag...

At work we use this stuff.

 

Im kinda getting the feeling the op wants to run some sort of insecticide device for a duration of 3 minutes every ten minutes that pass. wouldn't a simple 555 timer do the job? Like in the examples section at the bottom of the page figure 8. This is not the exact circuit to do the job, But I think it could be tuned by changing the resistor and cap. values to get the desired outcome. I bet Bill Marsden could probably throw the proper values off the top of his head..lol http://www.sentex.ca/~mec1995/gadgets/555/555.html

 

I just built this circuit for an xmas light tree top star project, but from experimenting with it to get the right flash pattern I learned a few things from it. The resistors circled in green controlled the duration of "off" time (sorry don't know the correct term), the capacitor in red controlled the on time of the lights. the +/- connections on the LEDs circled in blue could be used to drive any device as long as the current demand stayed within the range for the 555, I believe the max current for the ne555 I use is 200ma. The resistors beside the blue circles are just current limiters for the LEDs so they might need to be removed for your application. By playing with the resistor/capacitor combination, you should be able to achieve 3 on 10 off from it.. but I have no idea how to figure those values beside trial and error

 

If you're a hobbyist there will be lots of advice on here. All needing more information.

If not:
Here is a cheap one if you can wait a week.
Any voltage from 12 to 220, by request.

http://www.ebay.com/itm/INU-AC220V-...299?pt=LH_DefaultDomain_0&hash=item1e7f4a2083

 

I'm not sure a 555 is heavy enough to kill a roach. Maybe if you could fire it from a gun it would?

 

I'm not sure a 555 is heavy enough to kill a roach. Maybe if you could fire it from a gun it would?

don't be silly,, you have to place it on the roach first, them hit it with a book...geesh... but seriously, Wouldn't a 555 used in the manner I suggested work? Im truly curious about it as I am just learning myself