DIY automation

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Desterline

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Jul 18, 2014
63
Tucson, AZ
So, I've been chewing on ideas of reducing my daily maintenance effort... SWG are interesting, not entirely sure I understand how the liquidator works yet (suction side of filter pump plus a metering valve? Seems a recipe for inconsistent delivery) and then you have metering pumps (mostly Stenners, it seems). At the moment I'm having a hard time swallowing the cost for any of them. Commercial liquid chlorine dispensing seems a bit too expensive compared to SWG. Fairly close to the same price, but I still have to buy and carry the chlorine. A SWG is attractive, but I'f I'm investing that much (and dealing with salting the water), it really needs to be part of a whole plan to renovate the pad. So I'm considering low-cost DIY options.

Hoping it doesn't turn out like this:



It seems a lot of people are doing at least some amount of DIY with the Stenner pumps anyway, different timers and control schemes and different tank arrangements seem to be common. Is anyone doing anything interesting with different pumps?

I see this one from McMaster-Carr http://www.mcmaster.com/#43045k51/=tdlzjx for about $150 does almost 20 gallons a day (80 gallon a day version available for about the same price)

Then I was poking around e-bay and tripped on these: http://www.ebay.com/itm/Peristaltic.../291109659872?pt=BI_Pumps&hash=item43c77ce4e0 Rated 100mL a minute. If I did the conversion right, that's about 38 gallons a day. Best part is they're available for less than $10 shipped.
No word on chemical compatibility, but I'm thinking at that price I could probably afford to change the tubing out for something bleach-compatible. :)

Any thoughts?
 
I like stenner or SWG. I would do the stenner over the McMaster, price is close and the Stenner is a known quantity.

That ebay version would be a really fun experiment...
 
The ebay version lead me to this one on AdaFruit http://www.adafruit.com/blog/2012/12/19/new-product-peristaltic-liquid-pump-with-silicone-tubing/ which lead me to a couple interesting youtube videos of the pump in action and a teardown.

Looks to be using everyday silicone tubing in the pump which A) passes compatibility with bleach, and B) is cheap and readily available.


I would _like_ to do a SWG, but if I'm going through that effort, there's other things I need to do and it quickly snowballs on me. I'm limping along with a CYA over 500, and really need to drain and fill... while it's drained I really need an acid wash and some tile work... if I'm doing that, there's some cracks in the decking... I really should change my old pump out for a variable speed for the energy efficiency... If I'm moving stuff on the pad, I really should remove the abandoned gas heater... need a better cleaner connection... that old filter has issues... should re-route the backwash drain... the sitting wall really needs some love... the landscaping...:drown: Maybe I'll just stop by walmart for a couple more bottles of bleach.:rolleyes:

I'm a mild mannered pool owner by day, but by night I'm an electrical engineer that specializes in product development. My engineering sense is tingling and I know there's a better way to automate this....
We'll see
 
That is interesting. So the implementation details vary a bit, but basically just a bucket with a tube to the suction side of the pump and a metering valve. Frankly I'm amazed you're able to maintain consistent delivery volumes. Do you have enough chemistry data to back this up? I'm wondering if you actually have consistent delivery volume or if it just averages out over practical time frames. I'm also wondering about using it for bleach vs acid. Not just the immediate chemical compatibility, but the tendency to precipitate crystals and that blocking your "metering valves" (in whatever form) I see some of the posts in that thread were of people doing just that, but I didn't see much in the way of long-term results.

I went ahead and ordered one of the e-bay pumps and I'll be ordering some more tubing and fittings today. Worst case scenario is I'm out $20 and had something to putter with for a few days.


I'm chewing on another thought though. A hydraulically driven pump...



Other implementations are likely better, but the obvious concept is two hydraulic cylinders mounted end to end.
One is hooked to the pressure side of the pump and has a return spring, such that whenever the pump builds pressure it extends and when the pump looses pressure it retracts.
Use the other cylinder with a couple check valves as a bleach pump.
Every time the filter pump cycles you get one stroke on the bleach pump.
Adjustment could be (in addition to chemical concentration) stroke length and number of start-stop cycles of the pump.
Some type of metering valve to limit the rate of addition.

Have to play with the relative sizes, wouldn't want to have to cycle the pump very many times a day for practical delivery volumes.

A single chamber with a diaphragm is probably a more practical implementation.

(probably more thought experiment than anything I'm likely to actually build)
 
Desterline said:
Frankly I'm amazed you're able to maintain consistent delivery volumes. Do you have enough chemistry data to back this up? I'm wondering if you actually have consistent delivery volume or if it just averages out over practical time frames
Click to expand...
6 years worth of operation but I have found that short term consistency is not all that important as long as you take into account the swings which aren't really all that large. A manually dosed pool has very large swings in both PH and CL so if you compare this system to that, it is far more consistent. I usually test once a week but PH rarely varies much unless I change pump run time or the SWG run time. Two factors that affect PH. FC levels should be affected mainly by user load and UV extinction both of which are pretty easy to account for.

The other factor that affects draw rates are the pool valve settings. I have basically two settings that can affect the suction on the pump. Cleaner on vs off and solar on vs off. There is no acid draw in spa mode because of where I put the injection point. However, most of the time, I have the cleaner valve engage and solar only comes on for an hour or so a day which is fairly predictable so again, those things tend to average out and you quickly learn the worst case and simply set for that.

As for your pump setup, assuming you can get the hydraulic pump to work there, it would be subject to same pressure changes as the suction side setup so the draw rate would also vary with valve settings. So I don't see the advantage of adding the hydraulic pump.
 
I built a DIY peristaltic chlorinator that is controllable from my phone. It has worked flawlessly this first year and is kind of fun to use, but I'm not sure I saved any money over a Stenner.

$50 .. Watson-Marlow OEM peristalic pump w/ DC motor from ebay
$50 .. mbed microcontroller development board
$35 .. bluetooth radio module
$20 .. Solid-state relay
free .. 24V AC/DC power supply
$30 .. Stenner injector, tubing & suction line strainer
$20 .. 6" pvc pipe & cap (for housing)
$80(?) .. 15 gal tank

An app on my phone lets me set the target FC, burn rate (ppm/day), and enter my FAS-DPD measurements. The microcontroller continuously estimates FC using the burn rate and any measurements I enter, then injects as needed to keep the estimate within 0.1 ppm of target. I measure FC once a week and its usually spot on. Of course a swim party throws it off, so I do a measurement after the party and that brings it right back to target.

The white cylinder above the tank houses the pump and electronics.

11507170803_fb50e53ff3_c.jpg
 
Pentair SWCG and Simpool pH is a simple and effective solution in use down south. All parts available online and only part to replace is the probe once every 24 months. Calibration is quick and simple every 4 months.
 
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