Flow Switch?
 

Is there a flow switch available in either copper or plastic (that fits 1/2-inch tubing) which will allow me to automagically turn the system off if the pump stops pumping while I'm not around? Is it readily available/easy to find?

Can anyone think of any other way to tell (electronically) if fluid is moving through clear tubing (preferrably from the outside of the tubing).

Gentech international makes the FCS-01 and FCS-02 flow switch, which comes with 3/8" BSP or NPT thread respectively. They're made for automated drinks dispensers and are reliable and have little flow resistance. They cost £9,-- a piedce, but the difficulty is getting them in small quantities --they're made to order usually, by the thousands, and I had to beg and plead to buy ten (as low as they would go --and yes, I've sold the surplus already). They may also do 1/2" models, but probably without the thread.

Here's a FCS-01:

http://pic10.picturetrail.com/VOL332...4/26377841.jpg

...fitted on an Aquatube res. Note I had to drill out and tap (to 3/8" BSP) the Aquatube inlet to accommodate this switch. But it fits nicely.

http://pic10.picturetrail.com/VOL332...4/26377849.jpg

I'm connecting this switch to a bit of electronics made by electronics wiz Dr. Mike (a.k.a. bsodmike). It's a PIC driven circuit connecting to a bi-colour LED, that makes the power LED throb, iMac style, when the PC is off (blue in my case), shine continuously when the PC is on (still blue), but turn another colour (red in my case) if the pump fails. It simultaneously sends a shutdown signal to the PC.

The circuit in question comes on a PCB that connects to a standard molex and also incorporates a supply connection for a 12V pump (inc. interference shielding capacitor and diode, and a fuse). Which is nice. :D

Another way to measure flow without moving parts, is Gentech's ultrasound sensor. It's a little oblong black box with 3/8" thread openings on either end, through which liquid flows unrestricted as ultrasound sensors measure its flow (without coming into contact with the liquid). Rate of flow is expressed as pulse speed (like a fan-- so you could in theory hook it straight to the mobo?). It operates comfortably on 12V. the unit is a bit more pricey; expect to pay £90,-- ish.

http://www.zfz.com/pictures/temp/flow_switch.jpg

Go to page 4 of that article if you don't want to read it all. I'm now using it with Shutdown plus to force a hibernation on no or low flow and test it once a week. so far it's never failed to hibernate the PC within 30 secs of stopping flow

Bladerunner,

I had to use their "international" website, and the part doesn't appear to be listed. :/

www.rswww.com in the search box at the top left type C257076, works for me. or you can try the part no 257-076

my little brother came up with an ingenius way to solve this problem. at school he made a water sensor circuit and he placed it into the res on his PC where the water would splash up the side as the water flowed into it. he then hooked it up to the sleep button and low and behold, as soon as he shut off the pump the computer went into standby. he now has it set so that the computer shuts itself down safely when the standby button is tripped.

he sure is smart for a 12 year old.

Yeah, it works on their main UUK web site for me as well, but when you try to place an order, it dircets you to the "internationals site, and when I click the North America/United States option, iand then do a search for the part, it comes up with no matches (ditto on the manufacturer as well).

Well If you really, really, really want one, I could possibly be persuaded to sell you the one in the image :dome: I still have it somewhere. I thread tapped it and fitted 1/2" barbs to it, can't remember if I sealed the barbs in with aradite or not now I'd have to find it but I have a meeting at the bank tomorrow so I'm pretty busy doing accounts until then. It is unused other than testing, was destined for my shuttle w/c project but I can get another. :cool:

Read my article about it through to be sure you want one, and then let me know...

I looked around (both your website and here) and I can't seem to find an article that mentions that switch. Got a link? :)

The image I posted in my reply above is also a link to a full article, (on bit-tech), that has details on the complete flow protection system. (if you can't see any image then you have a add banner blocker or something similar in your firewall that's mistaking it for an add). My article includes details about the flow switch and how it's used in my system together with the pulse gen and MBM5 etc, (except I use the larger flowswitch in my system because of the pump used and amount of blocks / flow required in my system)> It looks and works in an identical way.

The one in the image is mentioned on the last page of the article btw..

nexxo, I like your circuit idea. Do you have a diagram?

Sorry, nope, but bsodmike, who designed the circuit, does. He is currently producing just a few one-offs, one for me, and probably one for himself. If you're interested, bsodmike an be found on Bit-Tech forums. E-mail him and he can probably show you. I'm sure he'll also be willing to sell you one if you wanted one. I have a .jpg of the PCB but he put a lot of time in developing this thing so I want to ask his permission to show it first.

Are their specs on it inner diameter or outer diameter?

And does it say 1.5L/minute or 1-5L/minute. B/c if its 1.5L/minute norminal rate, that's pretty damn low.

I like your sig :dome:

Well remember I only bought it, I didn't design it :p but I'm pretty sure it's 15mm OD, when i find the one i have I'll measure. It can't be 15mm ID because like I said in the linked article I tapped a thread in the body of the 15mm unit for a standard 1/2" barb, with 1/4bsp thread. There are two 15mm versions and my guess is it's just the "bobbin part", (the bit that moves up on flow to trigger the proximity switch), is just lighter on one type so it registers flow at a lower flow rate. The lpm rating is just a trigger point not maximum flow, if you are just using it to monitor pump death / flow loss then its fine.

Here is some of the best answers for your questions, is an article writen by RoboTech in a similar thread i had a couple of month ago.

Controlling Pumps and Initiating Emergency Shutdowns

Good article, I will do a hardware shutdown sometime as a last resort emergency, maybe CPU or waterblock temp controlled to interrupt the green wire. I prefer the initial software based system to force hibernation as it saves the PC's current state / work in progress. I also like to test it often so keeping pulling the plug on the PC when it's running is not good practise.

I also have a solid state optical water level switch, (rs code 183-543), that I haven't had time to set-up yet, again if it works as described should more reliable than any float mechanism.

Ahh, thank you for the clarification. I (hope) that RS can ship to the US, either that or I'll have them ship to my friend in eastham and he can shoot it over to me. Either that or I'll send it to Pug/Infidel and he can ship it over. ohhh the crazy things I do!

I'm glad you like the sig line.

If you get stuck I can probably get you one also, and if you intend to tap it to 1/4 bsp / npt then you'll really need some non taper fittings, or just die cut taper ones like I do. Let me know if you want more details on how I did the one in the image, it required care to avoid cracking the resin body.

@ Warlok: talked to bsodmike; you can e-mail (or MSN) him on: mike@bsodmike.com
He can give you all the details you want on the circuit in question. :)

I hadn't even gotten that far in my thinking as to how to get the fittings on it. Since the casing is plastic I'd probably get gray PVC or nylon or polypro 1/4 NPT 1/2" OD barbs and and attempt to epoxy/plumbers goop them in.

Aldralite is another type of plastic weld, yes?

What do you think of this method?

I'm never in favour of gluing anything, especially when its likely to be subject to water immersion. I just don't trust glues due to experience. With any glue the bond is always great right up until the point it fails :eek: I use araldite purely as a sealing agent that also strengthens the area / join. The barbs are held in by the thread pitch not the bond of the glue. About the only glue I accept as good enough on its' own is used to melt plastics together, like model kits or plumbing pipes for instance, but thats more like plastic soldering than gluing. Anyway I don't think this would work because the body of the unit is a resin based. What size / type of barb would you need in it anyway?

I've got 1/2" ID tubing all around, so a 1/2ID barb would be the best, but a 1/2" OD barb would suffice, so long as ream it out.

speaking of flowswitches, just got these:

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3803514447

should work pretty well i hope? for some reason the ones i got have way too many sensor wires

The ones you got may be sensors that connect to some central processing unit, rather than work stand-alone. But if you can tell us how many wires come out, that may give us a clue.

Keep in mind that with any type of flow sensor you have to look at its flow resistance, or "pressure drop". It's one more restriction in your circuit...

Got the rotorflow's
 

ok I got the sensors today. Here is the deal:

Those are these sensors here:
http://www.gemssensors.com/pdf/IOM_B...s/RFS-2500.pdf

They have 5 wires coming out 2 for power (12 VDC)
1 more is common and the other 2 are signals wires
1 Normally Closed (closes the loop between it and common when there is a set amout of flow)
1 Normally Open (opens the loop between it and common when there is a set amout of flow)

1 pot on the back that adjusts the amount of flow that will trigger the NC to open and NO to close

also an LED in the back that lights up when the threshold flow is reached.

oh yea they are $150 each got all 6 (one is 24 volt) for really cheap.