See post 15.

ooopsss... missed that one...
it's going to be much harder to devise something with an axial turbine, instead of a traversal wheel, as I had originally visualized it...

 

See post 15.

The curved vanes might make opto-interrupting tricky - and that colour molding might make opto-reflective just as difficult!

 

The curved vanes might make opto-interrupting tricky - and that colour molding might make opto-reflective just as difficult!

I'd probably just change the thing for a paddle wheel type, instead of putting too much work in this one.

 

http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=0K8AKGXN9XEEV2NA6WV0

It would be quite easy to use a simple light source and sensor mounted on opposite sides of a flow paddle like the one in the link. Yours is a little more difficult, but might be done.

This would be my choice short of getting into more expensive solutions like flow switches and sensors. With all the inexpensive stuff falling off the boats from China I have yet to see inexpensive flow stuff fall off the boats.

For $20 I would start with the above linked Roto-Flo Flow Indicator and glue a LDR and light source to it and see what you can come up with.

Ron

 

It looks like it dismantles pretty easily, if so I would look at embedding a miniature button magnet in one of the vanes and use a prox detector on the outside, I don't think the rpm is going to be that high to worry about imbalance, but if so another magnet could be used on the opposite vane.
SS400 $1.40 at Digikey.
Max.

 

It looks like it dismantles pretty easily, if so I would look at embedding a miniature button magnet in one of the vanes and use a prox detector on the outside, I don't think the rpm is going to be that high to worry about imbalance, but if so another magnet could be used on the opposite vane.
Max.

That's actually a very good idea... another possibility would be to drill a hole in each vane so that a light could be shined through them at an optical sensor on the other side...

 

I found these on ebay and wonder if one of these can work for what i want? http://www.ebay.com/bhp/water-flow-switch

 

I found these on ebay and wonder if one of these can work for what i want? http://www.ebay.com/bhp/water-flow-switch

Yes, they can do exactly what you want. Just make sure they're the size you want and are capable of detecting the minimum flow you need. And that they also work at the proper pressure range

 

Ok i will order a couple of these and play around with them
thanks again Paul

 

Hi Cmartinez the problem i see using the magnetic water flow switch is that when the pump is turned on
it takes about 15-20 seconds before the water reaches the flow switch.
and close the contact.
so the alarm will then be on.for that time so i will need a delay of power for that 15-20 seconds before the flow
switch is closed.
i found a delay power supply on ebay.
can this work? http://www.ebay.com/itm/12V-Power-ON-delay-relay-Module-Delay-circuit-module-/400494540934?
or is there another way of doing this. not sure if i have this right
thanks Paul

 

Hi Cmartinez the problem i see using the magnetic water flow switch is that when the pump is turned on
it takes about 15-20 seconds before the water reaches the flow switch.
and close the contact.
so the alarm will then be on.for that time so i will need a delay of power for that 15-20 seconds before the flow
switch is closed.
i found a delay power supply on ebay.
can this work? http://www.ebay.com/itm/12V-Power-ON-delay-relay-Module-Delay-circuit-module-/400494540934?
or is there another way of doing this. not sure if i have this right
thanks Paul

You mean there is no water in the pipe when the pump is turned on?
How fast of a response time would you want your circuit to have?

 

yes there will be no water in pipe for 15-20 seconds so a minute or two response would be ok. for the circuit to switch on.
thanks paul

 

So a solution that covers everything now has two parts. Part one looks at the pump and enables the alarm circuit only after the pump has been on for 20 seconds (see 947 previous threads about long time 555 circuits), and an alarm sensor that detects vane rotation and drives a beeper or flasher. I like the optical approach because the magnets probably will decrease the net flow rate through the inline sensor. There are lotsa ways to get reliable detection from the optical methods in previous posts, but it will take some fiddling around. All in all, this could cook down to three 555's...

ak

 

So the steps you want your circuit to follow is:

• Start a 20 second (adjustable) timer as soon as the pump is started
• After this lapse, start monitoring water flow
• If water flow stops, then sound off an alarm after 2 or 3 seconds
• Reset the alarm manually, or stop the alarm and start monitoring again if water flow is reestablished

Is that it?

 

Cmartinez yes that is it correct
paul

 

Cmartinez yes that is it correct
paul

Then that means that @AnalogKid is pretty much on the mark... about three 555's will be needed.

1. The first one will work as a missing pulse detector set for 20 seconds (adjustable) and will start as soon as the pump starts.
   
2. The second one will start monitoring flow immediately, making sure that one rotation of the flow vanes takes place at least once every two seconds, but it won't be able to sound off an alarm until after the first timer has expired.
3. The third one will be in charge of producing a sound in the form of a series of beeps, or a siren, that won't stop until the second timer detects flow again, or the user stops the pump, or the circuit is shut off.

I suggest an optical system that would work by drilling a small hole (about 1/8" diameter) in the middle of the vane wheel. A LED would shine through the hole to a sensor on the opposite side. A pulse would be detected by the sensor with each turn of the vane wheel. The type of LED and sensor (infrared, or visible light) is yet to be determined.
A magnetic/hall effect detection system would also work. But adding a magnet to the vane wheel introduces an additional component to the system that could alter its balance, or accidentally fall off... I like the optical approach better.

Check the attached document, there you will find lots (if not everything) of what you need to know about 555's for this project.

 

As most of these W.C. spindles are 3ph, I am guessing that you also have a VFD?
If so, you could look at incorporating the various I/O such as instead of a 20 sec delay, use an up-to-speed output signal to AND with your flow meter Normal condition and either inhibit motion and/or shut the VFD off, this also could monitor it when running.
Max.

 

As most of these W.C. spindles are 3ph, I am guessing that you also have a VFD?
If so, you could look at incorporating the various I/O such as instead of a 20 sec delay, use an up-to-speed output signal to AND with your flow meter Normal condition and either inhibit motion and/or shut the VFD off, this also could monitor it when running.
Max.

Yet another possibility would be to monitor the pump motor's rpm, which are bound to be higher if the motor is running on dry. Or maybe also monitor how much power (in amps) is being consumed. If the pump is running on dry, then RPMs would go up and Amps would o down.