John,
Thank you. I'll build this over the weekend and let you know how it
works!
---
You're welcome.
Just as an aside, you can use a 4020 or a 4024 instead of the 4060
that's on the drawing, as well as the HCMOS (74HC40XX) versions
(preferred) if you happen to have them around.
If you get into trouble and you need to do some troubleshooting to
bring it to life, here's how it's supposed to work:
U1 is a 7555 (CMOS 555) wired as a free-running 50% duty cycle
astable multivibrator, and it supplies clocks to U2 and U4 all the
time.
Pressing S1 momentarily will RESET U4 and the RS latch, U3B-U3C,
forcing u2-1 low, which will keep the outputs of U2 low (and the
motor driving relays inactive) until U4 times out.
U4 times out after counting 64 low-going clock edges, and when it
does, U4-4 goes high, SETting the RS latch and forcing U2-1 high.
U3A is a 2-input NOR gate, and since U2-2 and U2-7 are being forced
low while U2-1 is low, U3-1 and U2-4 will be forced high until the
first high-going edge of the clock gets to U2-9 after the latch is
SET by U4 timing out.
When that clock pulse gets to U2 it shifts the high on U2-4 to U2-2,
enabling OUTPUT1 _and_, forcing U3-1 low. U3-1 going low will
cause U2-2 to go low and U2-7 to go high after the next high-ging
edge of the clock. Since U2-7 will now be high, U3-1 will stay low,
and the next clock will make U3-2 low, U3-7 low, and U3-10 high,
Now, since U3-3 and U3-2 are both low, U3-1 will be high and the
three-phase cycle will begin anew with the next clock:
_ _ _ _ _ _ _ _ _ _ _ _ _ _
CLK _| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_
_____________________________________________________
U2-1 __|
___ ___ ___ ___ ___
U2-2 ____| |_______| |_______| |_______| |_______|
___ ___ ___ ___
U2-7 ________| |_______| |_______| |_______| |_______
___ ___ ___ ___
U2-10____________| |_______| |_______| |_______| |___
Finally, since you said you wanted about a 30 second 'ON' time for
each motor when the thing is operating and about a 30 minute pause
when you hit the PAUSE switch, that means there will be 1800 seconds
in each pause period and 30 seconds in each active period.
If we make the period of the clock 30 seconds, then the total number
of clocks we'll have to count up to get the 30 minute pause will be
1800s
n = ------- = 60
30s
Which is pretty close to what U4 counts up to, 64, so if you use the
pot to adjust the motor ON times to 30 seconds, the pause time will
be:
t = 30s * 64 = 1920s = 32 minutes.
Not bad.
