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An electric device that stops electricity when no water is
flowing, or preferably, when the water reaches a certain
height, in which case it could also automatically restart at a
set height.
There are many times where a float cannot be used to control
the pump, especially in external (non
submersible) pumps,
where the fluid is stored in a location that has only a small
opening such as a sealed barrel that only has a small opening
on the top. Also, a float can be non sensitive and get stuck.
I'm thinking in the line of a pressure gauge (cost's less than
one dollar) and a bit of electronics to set it.
Baked
http://www.ia.omron...roducts/family/241/
Floatless Level Controller [MechE, Jul 24 2013]
Different Approach
http://pumps.stanco...controlle/item-1141
[MechE, Jul 24 2013]
Pressure Sensor
http://www.sjerhomb...-Level_Features.pdf
[MechE, Jul 24 2013]
More
https://www.sparkfun.com/products/10221
varistor type [MechE, Jul 25 2013]
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Annotation:
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What's the first link. I don't understand the
product. |
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I didn't see anything on the market so didn't even
think of googeling for 'floatless''. Thanks Meche! |
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The third link uses the exact method that I'm
proposing, but seems like its geared towards large
fuel tanks or such. |
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I meant a SIMPLE (or say - simpler) gadget that has
an electric plug and socket, and stops the
electricity accordingly. Anybody who makes such,
it will sell next to all the none-submersed pond
and wine pumps, in all hardware stores. (There are
close to 1 million sold every year, so you'll be
making a nice profit. |
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The flaw with the second link's approach is that it
runs the pump on an empty tank, so pump
protection may not be so good. |
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The first is still a simple level sensor, it runs a low
voltage electric current through the liquid. If
there's liquid over the upper point, you get a
closed circuit and it triggers the pump. |
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The second will put a little more wear on your
pump, but it isn't intended to run the pump
completely dry, and not for very long once it
reaches that stage. As long as it's only running in
that state for brief periods, it shouldn't greatly
shorten pump life. I'll admit I don't think I would
implement it in a situation where there wasn't a
reasonably steady level of flow, such that the
timed turn on almost always found more liquid to
be pumped. |
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Based on the scale of the 2" mounting bracket in
the PDF image (and assuming even vaugely to
scale), that looks like a fairly standard sump or
septic tank application to me. The sort of bare
bones PLC control it appears to have is kind of the
minimum you'll find for purchased control systems
these days. |
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If you need a variable level reading, you can also
do it with an ultrasonic distance sensor in a
lookdown position, or a laser distance sensor, as
long as it's one that can detect your liquid (simple
if it's milk, more difficult if it's water). |
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If you just need a simple on-off at height, it's
possible with a retroreflective or thru-beam with
an opaque liquid. Feasible but not simple with a
clear liquid. More practical might be an
capacitative proximity sensor, which will work fine
as long as you have a non-metallic window to look
through (they can work through thin metal, but
they're touchy at best). |
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Use guilt. Put a caged kitten and a mini-cctv camera in the tank, with a monitor where people can see it. |
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not - you meant to post that on my cat-a-pull
idea. |
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MechE - thanks!! I was working two years back on
a fuel theft prevention device, and should have
remembered this solution. |
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The lasers are extremely expensive, even for the
simplest use. Pressure gauges are extremely
cheap, and not much less sensitive or accurate. |
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That last one looks fantastic! I sent the link to
some of my friends. |
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The thin strip liquid sensor from SparkFun looks interesting until you look at the price. A capacitive solution is much more economical. If you want to prototype it, I'd recommend a "PSoC 4 Pioneer Kit". It's got way more features than you need (including ARM processor), but for $25 it's got everything you need except a length of wire to use as the capacitve level sensor. For a simply binary level detect, just fold a wire in half so there are no exposed contacts in the liquid, attach it securely inside the tank so it can't move relative to anything except the water level and hook one end of the wire to a capsense pin. When the water gets high enough to touch the wire, the capacitance will change and the chip can detect that. |
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If you want to transition the design to small scale production, the chip is less than $2. For mass production I'd switch to a lower cost capsense specific part, but the dev kits for those are more expensive. |
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That's all you need to connect to a PC, but if you want to control some power directly, you'll need a relay. I easily found a 150VAC Arduino compatible relay shield for $8 that should plug in nicely. |
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There are off the shelf solutions to this, using
optical or ultrasonic probes. But they cost
rather more than a dollar. |
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You might be able to make a device using
standard IR LEDs for about USD$5 … the
works out of a standard computer mouse
with quadrature encoders using IR LEDs
would be a good starting point. |
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