Hello All!
So I got it in my head to build this timer to control a small pump (120vac, 20w max). I could buy one for between $80 and $170usd, but don't want to spend that much and thought the project would be fun. Well i sorta built what i needed with an RC circuit and a lm555 timer ic connected to a relay. It definitely works, but the intervals are WAY too short. So i need some ideas on how to increase the cycle frequency upto about a maximum of 12 hours. (Well past the leakage threshold of my RC timer)
I don't have a PIC programer so I'd like to stay away from mcu's. I would like to use two pot's to control the off and on intervals. Control voltage can be anything between 3.3 and 18vdc.
My basic idealized circuit would be voltage regulator>timer>npn switching transister>relay. Obviously there are resisters, diodes, caps, and pot's to be added as well, but that is the basic idea i have.
Thanks for any help anyone can offer.
BTW:
I found two ic's that do what i want but they seem VERY expensive. Still maybe their datasheets will help clearify what i am asking for help building.
ICS Inc's kd6 series: http://www.ics-timers.com/pdfile/Repeat.pdf
and
Amperlite's adjustable HDFA: http://www.amperite.com/assets/Documents/hdfa.PDF
Example of commercially available timer: Green Air Products 4P Cyclestat timer
So I got it in my head to build this timer to control a small pump (120vac, 20w max). I could buy one for between $80 and $170usd, but don't want to spend that much and thought the project would be fun. Well i sorta built what i needed with an RC circuit and a lm555 timer ic connected to a relay. It definitely works, but the intervals are WAY too short. So i need some ideas on how to increase the cycle frequency upto about a maximum of 12 hours. (Well past the leakage threshold of my RC timer)
I don't have a PIC programer so I'd like to stay away from mcu's. I would like to use two pot's to control the off and on intervals. Control voltage can be anything between 3.3 and 18vdc.
My basic idealized circuit would be voltage regulator>timer>npn switching transister>relay. Obviously there are resisters, diodes, caps, and pot's to be added as well, but that is the basic idea i have.
Thanks for any help anyone can offer.
BTW:
I found two ic's that do what i want but they seem VERY expensive. Still maybe their datasheets will help clearify what i am asking for help building.
ICS Inc's kd6 series: http://www.ics-timers.com/pdfile/Repeat.pdf
and
Amperlite's adjustable HDFA: http://www.amperite.com/assets/Documents/hdfa.PDF
Example of commercially available timer: Green Air Products 4P Cyclestat timer