Re: 555 timer problem

Yeah that looks like it (or its many cousins) could work.

Since you seem to be playing with 555's and battery power, I figured
this was more of a project to satisfy curiosity or for self
satisfaction (low budget toy).


Well, I'd like the unit to cost as little as possible, because I'll
probably be making a bunch and giving them as gifts (very expensive
gifts). I might try to sell a few on eBay... considering the ones on
the webpage sold for $400 each, preordered (for 6-8 weeks in the
future, which is about now). So a pump under $50 would be great.

And chemical metering pumps do tend to be expensive. They are made
for chemical, pharmaceutical, industrial applications and those people
have lots of money - and it ain't exactly a common item. They want
absolute accuracy, a pump that will run for a long time before
repairing, and usually in a harsh environment - that costs.

I've looked on about 20 of these chemical/pharmaceutical/misc "fluidic
specialists" websites and found lots of suitable pumps.. but only one
site had a listed price (I've 'applied' to all the others, with as best
specifications as I could.)

Perhaps you could help me with this. Take a look and read their
descriptions:

http://www.hargravesfluidics.com/air_pumps.php (look for the CTS
models)
and
http://www.hargravesfluidics.com/liquid_pumps.php

The store for the CTS pumps is here:
http://www.hargravesfluidics.com/store_cts.php
and for the liquid is here:
http://www.hargravesfluidics.com/store_ltc.php

The LTC pumps cost double, and need at least 12volts. So I've ruled
them out.

However, the CTS pumps look like they could work. Especially the "low
flow" pumps at the bottom. I've measured the flow row of my fountain
when it drips at an optimal rate, and it turns out to be about
..08mL/minute. I measured it by weighing a cup, filling it for a minute
with the perfectly dripping stream, then weighing it again. I'm
assuming my tap water/highliter liquid solution is approximately 1g/ml.

Anyway, the problem is the CTS line of pumps doesn't explicitly say it
is meant for water. I'm wondering it will work anyway. I sure hope
so, because I'd love to order one right now and get this thing working
and very stable. I'd love to get rid of this valve and replace it with
just controlling the PWM. Which leads into my next question, PWM
should work the same with these pumps, right? It won't adversely
effect performance, will it?

And yet another question.. will the pulsation of one of these pumps
affect the unit? I mean, do you think it will vibrate enough to shake
the whole foutain and cause some disruption of the drops? I noticed
they work with a weight off the shaft of the motor which seems like it
will cause some wobble. I'm assuming that since it's so small it won't
do much.

On a side note, I found it astonishing how well these pumps react to
pressure! They can pump water really high for being so small. My
little impeller pump here has such a huge drop-off when the height of
the fountain is raised. But I guess thats the principal behind
"positive displacement," theres no way for the water to go but out the
pump.


I haven't been following the whole thread, so I haven't kept up with
your quest. I was off for a week with the wife too . . . Is this,
are you building a water clock?

I hope you check out the video.. it shouldn't take longer than 5
minutes to load.

You mentioned something about viscosity and drop size? I was a kid
and watching TV in the 50's sometime. There was a show called "You
Asked for It." Someone wanted to know what the largest drop size
was, and they sure produced a prodigious drop. They showed people
climbing up a ladder and dumping buckets into this large (6-8 foot
diameter) ring with about a three foot height. The "drop" formed at
the bottom of the ring and went into a huge tub.

Well this thing, if my memory is right, was just a ring with a very
fine mesh screen at the bottom and a layer of cloth resting on the
screen. They had to start it off carefully by wetting the cloth until
they had a few inches of water in it then just dumped buckets in it
until it drop 'd through the screen. You could see the drop forming
long before it dropped and it looked like it held a few hundred
gallons. The ring was formed with a "bell" opening where they were
pouring water, and it looked like the drop formed below with some
margin - like there was a rim or something that prevented the drop
from going out to the edge of the ring.

That was a long time ago. I was a kid. It was a black and white TV
and on an antenna - so perhaps there are gaps in my memory.

They didn't say, or I don't remember, if they had any way to increase
the surface tension of the water - I think not. I think the whole
idea/experiment was predicated on the same idea as used by aerators on
faucets.

I'd love to learn how to make bigger drops using this method. I'm
content with the current drop size, though. I might upgrade it by
putting a piece of McDonalds straw (aka soda-pipe) at the end, since
its much wider.

As per the pump made from the aquarium pump... I'll look into this but
I'd prefer a plug-and-play solution at this point. I'm hoping one of
the several pump places I've contacted will be friendly enough to be
like "we've got just the right pumpt for you... and it's a very common
one. It'll be $30." We'll see, and I'll definitely keep you all
posted.

Again, thanks so much for keeping up with this!

-sam

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