looking for a 555 timer circuit

I'm looking for a circuit that would utilitize a 555 or similar that
will have 3 120VAC outputs that it alternates between. This would be
used to drive 3 powerheads (water pumps) on a fish tank to create some
wave motion in the water. I would think that the time it alternates
could be varied based on a rheostat. Also, if possible, I want to have
a pushbutton that would stop all 3 pumps for 30 minutes or so for
feeding (push the button, power is killed for 30 minutes to the pumps,
then they startup again automatically). So, probably would be 2
circuits. Anyone have a design for something like this or can help?

TIA

 

Although the guys for whom solder is a favorite programming language may
have different ideas, I'd do this with a small microcontroller. One A/D
port to read the rheostat, a digital port to sense the pushbutton, and
three digital outputs to control the power to the pumps.

Could probably be done with an 8-pin ATtiny15 (same size as the 555)
which has an internal oscillator, a couple of timers, and four A/D
channels plus the rheostat, pushbutton, relay drivers, and relays.

 

I'm looking for the solder version :^) I have most of the parts on
hand to build this, just not the knowledge of where to put the parts.

 

Take a look at the "555 Designer" at:
http://www.schematica.com/555_Timer_design/Timer_Comparison.htm The
"Pro" version isn't very expensive and has some helpful "wizards" that
will at least give you some ideas, including I/O circuits, long interval
timers, variable timers, and so on.

 

555 -> 4017 -> 2N4401 -> relay coil. Set up the 4017 so the Q3 output
resets it. Also, use one of the timer-counter chips, like a 4541, to
inhibit the entire circuit using yet another relay for your 30 minute
pause...

The datasheets for these chips and transistors are freely available, and
usually have application schematics in them that are close to what you are
interested in. If you need more help, post again.

Note that you'll need a DC supply for the logic, which won't run on AC.

--
Regards,
Bob Monsen

"I cannot persuade myself that a beneficent and omnipotent God would
have designedly created parasitic wasps with the express intention of
their feeding within the living bodies of Caterpillars."
-- Charles Darwin

 

Would something like this work: I'm looking at the samples shown on
http://www.uoguelph.ca/~antoon/gadgets/555/555.html. I was thinking of
using the '10 minute timer' to power a second circuit consisting of the
'555 timer tester'. Instead of powering the red LED in the timer
circuit, I would have that power the tester circuit. In the tester
circuit, I would substitute solid state relays for the LEDs. Is this
feasible?

Assuming so: The timer circuit isn't exactly what I want, but close.
Can someone show me what to change to make it 'default' to power on
(across the red LED), and how do I calculate what value of resistor to
use in place of the 500k resistor to get approximately 30 minutes of no
power across the red LED?

In the tester circuit, if I substitue a pot for R2, would this allow me
to adjust how long the relays would be powered? I would want equal
times (or as close as possible) of about 30 seconds on and 30 seconds
off. Ideally, I would want 3 outputs instead of 2, but this is a
start.

Hope this makes sense, and thanks for any help anyone can offer.

 

Why? Fish can't eat when there are waves?

--DF

 

haha. They can, but corals and some slower moving fish/creatures in
saltwater environments need more time to catch food before it's
filtered out.

 

---
I'll help you, but I don't understand the pump timing. In your
earlier post you said that you want the pumps to turn on
sequentially, which I took to mean one at a time, like this:
_____ _____ _
PUMP 1 __| |____________| |___________|

_____ _____
PUMP 2_________| |____________| |_______

_____ _____
PUMP 3_______________| |____________| |_


However, above, you said that you want the pumps to be on for half
the time and off for half the time, so you'd be talking about
something like this:
_____ _____ _____ ____
PUMP 1 __| |_____| |_____| |_____|
_____ _____ _____ _____
PUMP 2 |_____| |_____| |_____| |__
_ _____ _____ _____
PUMP 3 |_____| |_____| |_____| |____

where more than one pump would be on at a time, and the circuit
would be much different than for the first case.

 

An alternate approach that might turn out to be easier if you persist in
your perverse dislike of microcontrollers (insert smilies here as
required to assist any humor-impaired readers) is to drop back to an
older method of implementing long period timers: motors, gears (or
belts), and a cam shaft. Think of a music box or washing machine timer.

There would still be a 555 but this time (no pun intended) as a PWM
generator that controls the speed of a small DC motor. The motor,
through suitable gearing, turns a cylinder through one complete rotation
every "wave cycle." High spots on the cylinder press against
microswitches that in turn actuate the relays that handle the high
current needed for the main water pumps. Fine tune the rotation period
with a standard 555 PWM circuit.

The half-hour feeder timer could be a similar gizmo. Turn it to the
starting position that shuts a microswitch controlling a double throw
relay. The NO position of that relay would run another motor (and 555
tuner if required) until it reaches the low spot which opens the
microswitch, opens the relay, and stops the motor. The NC position would
be in the power path for the water pumps. While it's open, the pumps are
off. When the half-hour relay drops out, those contacts shut again and
the pumps start up.

With the cam setup, it would also be pretty easy to cut more complex
wave profiles with, e.g., more dwell time for the pumps on either end of
the tank than the one in the middle, simulating (roughly) simple
harmonic motion that "sticks" more at the extremes and moves more
quickly through the center.

 

John,

No, you are correct. What I want is what you show in the first timing
sequence.

 

---
OK, it's on alt.binaries.schematics.electronic under "Looking for a
555 timer circuit".

The outputs are positive true and should be able to drive a
solid-state relay each.

 

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.

 

---
Aarghhh!!!

I just saw how to get rid of the 7555.

Use S1 to RESET the 4060 and the rest of the circuit, and then when
S1 is released, use the 4060's front end for the oscillator it's
supposed to be. Then use its LSB to drive the '175 and use its Q9
to drive the latch. Or something like that. I'll work it out and
post the new schematic tomorrow.

 

John,

Is C1 100 F, or should it be 100 uF?

 

Ok, I'm holding...

 

Got the update. RevB is much cleaner. Thank you for doing this.

 

---
You're welcome.

In going over the circuit for the last time, (LOL) I found a few
errors:

1. U2-5 should be connected to U1-3, not U1-1

2. C1 should be an 0.18µF polyester cap.

3. R1 should be a standard 2 megohm +/- 5% 1/4W carbon film
resistor.