Soft start for 110V AC water pump?

[Pszemol]

Anybody knows some tested solution for a DIY wavemaker device
which would switch two or more AC-powered water pumps
(about 40W-90W each) in a 10 seconds cycle with a soft start
feature? I would be able to variable pump speed using variable
frequency of supply AC power. I would like the switch to start
with low frequency, lets say 10Hz and gradualy go up to 50-60Hz
during 1-2 seconds and then keep the pump running for 10seconds.

I was thinking about modifying an old UPS I have which is APC 280
for this purpose. Anybody here has any schematic for such devices?

 

[mike]

Anybody knows some tested solution for a DIY wavemaker device
which would switch two or more AC-powered water pumps
(about 40W-90W each) in a 10 seconds cycle with a soft start
feature? I would be able to variable pump speed using variable
frequency of supply AC power. I would like the switch to start
with low frequency, lets say 10Hz and gradualy go up to 50-60Hz
during 1-2 seconds and then keep the pump running for 10seconds.

I was thinking about modifying an old UPS I have which is APC 280
for this purpose. Anybody here has any schematic for such devices?

What kind of motors are these?
You have verified that running them from 10 Hz. will give you what
you want?
Depending on what you're trying to do, you might find a hydraulic
solution more feasible.
mike

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[James Meyer]

What kind of motors are these?
You have verified that running them from 10 Hz. will give you what
you want?
Depending on what you're trying to do, you might find a hydraulic
solution more feasible.
mike

I agree Mike. Trying to do it Pszemol's way is going to turn into a big
can of worms really quickly.

I assume it's some sort of wave synthesis for a saltwater aquarium. If
so, then running a small pump continuously to fill up an auxiliary tank placed
above the level of water in the big tank that can be dumped into the big tank at
10 second intervals would be a lot easier.

You don't even have to use a valve to do the dumping. There is a type
of syphon that can be used that allows a tank to fill and then the syphon starts
and empties the tank. The tank has to fill again before the syphon does its
thing again.

Jim

 

[Pszemol]

I agree that hydraulic solution is more feasible in most cases
but I have very small fish tank in my livingroom (30 g) and
there is no much room for a dump bucket nor I do not want
to have big splash of water on my carpet
The idea behind electric wavemaker is to switch water pumps
alternately and this works fine with the exception of loud
pumps turning on/off and shortened life of their impellers.
The workaround is to have the pumps start slowly, and many
expensive wavemakers are equiped in "soft start" feature
which is giving a variable frequency voltage to the pump
synchro motor causing it to turn more slowly at the beginning
and reach full flow rate in about a second or two. This way
you reduce the noice of impeller starting instantly full speed
and you extend the life of the pumps without sharp starting.

Since I would like to play with making some DIY wavemaker
out of what is in my basement (a couple of old computer UPSes)
I was seeking for some inspiration in this newsgroup...
If I could reuse boards from my APC 280 UPS to make such
wavemaker it could be great. Any idea on how can I aproach
this task?

Also, I have read somewhere that when I start this kind of
synchro motor slowly with lowered frequency I need to lower
voltage also to not burn the motor. Anybody knows what
would be the formula for the voltage for 20 Hz 40Hz when pump
is accepting full 110V for 60Hz frequency?

 

[Peter Bennett]

I agree that hydraulic solution is more feasible in most cases
but I have very small fish tank in my livingroom (30 g) and
there is no much room for a dump bucket nor I do not want
to have big splash of water on my carpet
The idea behind electric wavemaker is to switch water pumps
alternately and this works fine with the exception of loud
pumps turning on/off and shortened life of their impellers.

How about a mechanical solution: place a "false wall" at one end of
the tank, pivoted at the bottom of the tank (or just held against the
real end wall by gravel), and arrange a motor, crank, and pushrod
assembly to move the top of the false wall back and forth.

 

[Pszemol]

How about a mechanical solution: place a "false wall" at one end of
the tank, pivoted at the bottom of the tank (or just held against the
real end wall by gravel), and arrange a motor, crank, and pushrod
assembly to move the top of the false wall back and forth.

Interesting idea... I will think about it.
The problem is that it takes valuable space inside the tank.

 

[Rich Grise]

(why is this font so fat?)

Are you just trying to make water slosh back and forth? What about some kind
of
auxiliary tank, behind the main one, with the slosh baffle in it.

It seems like modifying two motor speed controllers, and coming up with
some kind of control circuit, would be way more work than you'd need,
just to make water slosh back and forth.

What if you mount the tank on a fulcrum, so the whole tank can seesaw
back and forth? It wouldn't take much movement to make some pretty
good waves!

Good Luck!
Rich