Sewer Pump Monitor rev 3.0

I haven’t posted any of my projects here yet; this will be my first. I recently completed my latest version of the Sewer Pump Monitor (SPM). Before going further I should explain the purpose of the SPM.

Since I live on an acreage in Alberta I have my own septic system; tanks and field. Depending on the snow cover when the deep freeze begins, I may have trouble with laterals freezing. And before the new system was installed, I had to deal with pebbles being picked up by the pump and stalling it. This happened twice and cost me a pump. To deal with these problems I built the SPM. It monitors pump current and pump time. If pump time exceeds 350 sec the pump is stopped briefly, then turned back on. This action causes a 4-way valve to switch to a new lateral. When pump time is exceeded an alarm is produced locally and throughout the house and shop via 60Hz FM intercoms. Keeping track of pump current alerts against bad bearings and the degree to which a lateral is blocked. Fortunately there are no pebbles picked up in the new system.

The build started with an aluminum box to house the MCU board, intercom, Hall effect current sensor, solid state relays and barrier strips. The MCU board is from the Northern Alberta Institute of Technology where I used to be an instructor. It has far more horsepower than needed for this project but it also contains needed components, namely: a RTC battery backed, nice 4 line backlit LCD, bipolar supplies for op amps, buffers for external outputs and an expansion area to build a signal conditioning circuit.

In Photo 6 one side of the box has been machined for cable clamps using my AVID 24x48.

In Photo 7 the box is complete and some parts are installed. The current sensor is mounted on the left side of the box. The 60Hz intercom is at the bottom. Solid state relays are above the intercom. There are 2 SSRs: one for the pump and one for the intercom, which is off mostly and on for alarms.

In Photo 8 the MCU board has been installed. The duplex outlet and cord with alligator clips are just for testing.

In Photo 5 I show a close-up of the signal conditioning circuit. A single quad package implements a precision rectifier, a low pass filter and an offset adjust circuit.

In Photo 9 the finished box is shown. The large holes provide access to Reset and a 5 button array for setting the RTC. The grid of small holes below the LCD is for the beeper.

In Photo 10 the unit mounted on the wall and hardwired in.

In Photo 11 the first real operation of the SPM is captured. Yes, at least one lateral is frozen.

The photos shown here accompany an article that will appear in Digital Machinist some time next year.


It looks great! Nothing like knocking out a project like this. It just feels good and there is something to knowing that if it doesn’t quite work the way you want, or in a year or two if you want to add an extra feature or control, you can just go in and edit/add to it. :slight_smile: Nice Job!

Thanks. It’s always nice when someone else appreciates one’s work.

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I am doing a box for my controllers right now so I have a bit of understanding the work and planning that goes into this.

Looks really pro!

Thanks John! I’ve made quite a few boxes over the years and I was really happy with this one. Having a CNC for the front panel is a real step up.

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Cool, unique project!

Thanks David! Managed to get the box built without making any scrap.

Love to see CNC and electronics in one project. Question - and not antagonizing, to be clear - why build vs buy? A metal box with punchouts is readily available. I much prefer this style, personally, but my ‘get-r-done’ gland would be screaming to just pick one up. :smile:

Thanks David! Regarding build vs buy, the answer is not simple. I do buy enclosures for projects; Hammond and Bud make some nice ones, but metal boxes of any size are expensive. Often the sizes just don’t fit what I need. So for this project I didn’t even look, I just built what I needed. Did I save any money? Not sure. But I did get compliments from my buddies and from some of you folks. What’s that worth in $? Again, not sure.

Rock on - it looks better than any box I’ve seen on the shelf.