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Brad Fitzpatrick

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AC switching, monitoring... [Apr. 13th, 2007|02:28 pm]
Brad Fitzpatrick
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My sewer's sump system has 3 pumps...
  • 2 in big tank. These have float sensors and only turn on when the fluid level is high enough. Only one needs to be on at a time. Ideally, I should have a switch box install that makes sure only one gets power at a time, switching it back & forth every so often. Otherwise if one is installed just a millimeter above the other, one will always get all the work and the second will never go, and so they won't wear equally.
  • 1 in little (rainwater?) tank. Also has a float sensor.
My deck is currently still torn apart because I'm still paranoid that once I close it, something will break again and I won't notice.

I'd like to be able to remotely monitor (and/or get alerts) about the pump health.

Here's what I propose (and what I need help on)....

Small Linux box (Mini-ITX or Gumstix) in a water-proof box, with WiFi, with serial ports (or Serial over USB), controlling X10 Universal Adapters (if they're strong enough for the amperage?), or controlling some relays.

So yes, I could do the switching between the two tanks from the computer with just a remote relay control, including varying the offsets, such that one pump doesn't always get the same hours of the day, but what I actually want to do is measure the power draw per-pump.

Basically I want to make sure the pumps' floats and motors are still working, by measuring the power draw on each of the three plugs.

Any ideas how I can measure this?

I'm also willing to pay somebody to build me some Serial/Parallel/USB device to do this, if any CSE-types are out in the audience. I'd rather spend a couple hundred on a solution that makes me happy, than spend a few hundred on a switching box and seal up the deck and never know if it's going to blow up again (or already has!).


[User Picture]From: hughe
2007-04-13 09:50 pm (UTC)
i recon it would be better with a pic chip or the suchlike.

remember if the motor is stalled it takes more current than normal, but if it has failed for another reason it might take no current at all:

You would have to check the current is within a set of parameters.

are you going to get it to email you /sms you if they stop working?
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[User Picture]From: brad
2007-04-13 09:52 pm (UTC)
I was curious about that! Yes, I'll check within defined parameters, definitely.

I was going to poll it from a separate machine, and if the poll fails, or the poll returns FAILURE, then email me, sms me, etc.

Hence the wifi, so I can just have a public health check interface. I don't really want to run ethernet out there, although I suppose I could.
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[User Picture]From: scsi
2007-04-13 09:53 pm (UTC)
How about a manual rotery selector switch on the deck with a light when the pump kicks on. Every other month you flip the switch to the other pump and just run some water in the shower and see if the light blinks on when the pump fires off.
Not as cool, not as fun or geeky, but when dealing with shit and sewage, you want failsafe and simple.
Though with the proper pumps installed (finally) you wont have any problems now they arent running 24/7.
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[User Picture]From: brad
2007-04-13 10:07 pm (UTC)
Huh, how do I get a light to turn on when the pump kicks on?

And how do I monitor the health of pump #3, which doesn't need to be alternated with another pump?
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From: (Anonymous)
2007-04-13 09:54 pm (UTC)

recommend serial relay

I blew an X11 'appliance module' doing some automated stuff like this. It died after about a year of 2-3* daily toggling.
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[User Picture]From: nick
2007-04-13 09:57 pm (UTC)
why don't you just install a trap door in the deck?
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[User Picture]From: brad
2007-04-13 10:05 pm (UTC)
There is one. It's small and gross and once I'm down there, it's a lot of work unplugging stuff one at a time, waiting for tank to fill, waiting to hear the pump noise, etc. And brining a hose down too to fill the other.

It's something I could say I'd do regularly, but never would.
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[User Picture]From: nick
2007-04-13 10:15 pm (UTC)
I guess my other question is why do you need/want to balance the load? Just run the bitch till she explodes. The problem before was that neither pump was strong enough on its own so you didn't really have any redundancy, right? So why not intentionally just run one pump and then hook up some kind of siren or flashing light or something to your backup pump so it's obvious when something is wrong with your primary pump (it's hopefully not something you gotta worry about except like once a decade at most).

I'm with your mom and frank on this one... there is definitely such a thing as too elegant of a solution when messing around with shit.
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[User Picture]From: sandy
2007-04-13 10:03 pm (UTC)
They sell warning systems that can be installed with septic systems. Why not contact someone to see what they can do for you, before you reinvent the wheel, which I know you like to do.

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[User Picture]From: brad
2007-04-13 10:04 pm (UTC)
Other wheels are stupid and expensive. Seriously expensive for how stupid they are.
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[User Picture]From: joggingguy
2007-04-13 10:47 pm (UTC)
I'd just wire both pumps to run from a single float switch and be done with it. Add a neon pilot light across the motor connections to know when it is running. Put it where you can see it through the deck boards :-)
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[User Picture]From: brad
2007-04-14 01:33 am (UTC)
The floats & pumps are basically one unit. Not something I'm going to crawl into the shit tank to mess with, in any case. Plus then there'd be one single point of failure.
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[User Picture]From: travisd
2007-04-13 11:01 pm (UTC)
Power monitoring: Check into one of the smart power strips that they sell for racks -- like what APC sells. Should have SNMP/Ethernet. Should be able to control the outlets as all if the need arises.

I'd say that what you really want to switch is the trigger mechanism, not the power. Always power the pumps, but have a DPDT type of arrangement that switches the triggers between the pumps. This way you can set the current "backup" pump switch a little bit higher, and it stays active as a backup.
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[User Picture]From: spottman
2007-04-14 12:14 am (UTC)


US Distro:

I use these to monitor VERY remote radio repeater systems, their batteries, reboot radios remotely etc... Just run POE to the device over one ethernet cable.

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[User Picture]From: brad
2007-04-14 01:35 am (UTC)
Whoa, that looks at least damn promising. I gotta run now, but I'm going to look into that more later, thanks!
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[User Picture]From: bandicoot
2007-04-14 04:06 am (UTC)
Plumbingsupply.com has this page on water alarms/level switches/sump pump controls. There's some interesting stuff there. I'm going to use one of their float switches in my water storage tank to control the well pump.

They also reference another "More alarms" page that contains a switch that alternates between two pumps, but it's almost $600.
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[User Picture]From: loganb
2007-04-14 06:43 pm (UTC)
Suprisingly, a google search didn't reveal any home products designed to wirelessly measure power consumption.

You could use a PIC microcontroller to measure the current with a Hall-Effect sensor, control relays that trigger the pumps, and talk to a computer via RS-232 (where you do all the hard stuff). PICs can be programmed directly in assembly or you can buy a kit at Fry's aimed at kids that has a BASIC interpreter loaded onto the chip, includes the programmer, etc.

Actually, why bother to measure the current? If the float sensor is triggered, start a pump. If the float sensor doesn't turn off in like 30 seconds you know the pump is bad and fire up the other. Then, you need a PIC that talks RS-232 and you only need to program it to turn on/off three relays, monitors the float pumps, and takes commands over the serial port.

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[User Picture]From: brad
2007-04-14 06:46 pm (UTC)
The float and pump are kinda one unit, iirc.
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