Author Topic: Flow measuring device  (Read 8503 times)

Offline yorkie_chris

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Flow measuring device
« on: July 13, 2011, 01:42:28 PM »
I'm wanting to make a fuel flow monitoring device, the only workable idea I have so far is for something resembling a hydraulic motor. A vaned rotor in a close-fitting housing with an inlet and output port within a tangent to the outer diameter.

The shaft would have a toothed/slotted disc on it for an opto-encoder to pick up.
The sort of flow rate we're looking at is between 30-400ml/min approximately.

All the things I can find meant for the job seem expensive or massive, and as it's for a bike there isn't that much room, and I'm poor.

Has anyone built one? Does anyone know if the bare flowmeter modules are available cheaply? Any ideas of parts that could be scavenged from elsewhere?

Offline jim

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Re: Flow measuring device
« Reply #1 on: July 13, 2011, 01:51:48 PM »
is this for a gravity fed system?

if i'd thought it through, i'd have never tried it

Offline Noitoen

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Re: Flow measuring device
« Reply #2 on: July 13, 2011, 04:50:17 PM »
You could build a small gear pump style flow meter but with the body made of acrylic plastic and no output shaft. Mount the optical sensor to count one of the gear's teeth. If the engine has fuel injection, you can build a sensor to "add" the injector activation period which is proportional to the fuel injected.

Offline BillTodd

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Re: Flow measuring device
« Reply #3 on: July 13, 2011, 05:39:53 PM »
With a little effort, you might be able to use one of these thermal flow sensors (~25):

http://uk.farnell.com/ist/fs1l-0-1l-195/flow-sensor-fluids/dp/1266954

Bill

Offline yorkie_chris

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Re: Flow measuring device
« Reply #4 on: July 13, 2011, 06:05:24 PM »
Unfortunately it's for carb bike, so no chance of getting fuel flow rate by adding up injector durations or anything.

is this for a gravity fed system?


Yes

Offline tomrux

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Re: Flow measuring device
« Reply #5 on: July 14, 2011, 05:14:27 AM »
Farnell flog a transducer should get you close to what your after.

http://au.element14.com/digmesa/932-9506-b/flowmeter-fhksc-arnite/dp/8544700

Tom

Offline picclock

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Re: Flow measuring device
« Reply #6 on: July 14, 2011, 06:04:25 AM »
@ yorkie
Vaned rotor is the way to go, but no opto. Just fit small earing type magnets to the outside edge of the vane (in pairs so they balance), make the housing of plastic, then fit a magnetic sensor on the outside. That way the vane rotor and it's bearings are fully enclosed with no chance of leaks or fuel contamination.

Integrated hall sensors are cheap, 5 for 5 on fleabay and should give good results. Best to get the ones with hysteresis. You will then need to display the info - but I assume you have something in mind for this.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline yorkie_chris

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Re: Flow measuring device
« Reply #7 on: July 15, 2011, 12:58:36 PM »
Seems that farnell one is Ok but flow range may be a bit narrow, seems that one works with the inertia of the fluid hitting the rotor. Also I can't see anywhere on sheet whether it is suitable with petrol.
I may make a similar thing just with a close fitting rotor, more like constant volume pump to better measure at low flow rates.


Why hall effect rather than opto? I've got some experience using them for speedo setups on the bikes (in fact will be one involved in same thing) but never at small scale like this.

I was thinking if I went opto I could use an ally case and drill right through, LED one side, sensor the other and pot them both in there with some epoxy.



Actually my first serious electronics project. Thinking of going with Atmega8 chip linked to a 2x16 lcd screen. I want to display current mpg, trip mpg, litres used and battery voltage. I think there should be enough capability in there for that.

Offline picclock

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Re: Flow measuring device
« Reply #8 on: July 15, 2011, 03:12:10 PM »
hi Yorkie

That sounds like quite a project to undertake.

With a magnetic sensor (hall effect) its easy to have a physical barrier between the fuel and the measuring electronics. If you use an opto sensor you either have to measure the interruption of a path of light or a reflection.  This means that you will have to use glass or transparent plastic to monitor the rotor, unless you have the shaft come through the casing with some form of mechanical seal (never a good idea with flammable liquids). Also, magnetic sensors are immune to changes of ambient light which can cause issues.

Most modern car speedo's now use hall effect sensors to replace the flexible spiral cable.

Good luck with your project

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline yorkie_chris

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Re: Flow measuring device
« Reply #9 on: July 15, 2011, 03:24:19 PM »
So with a couple of powerful magnets embedded in the lobes, will that work a hall sensor even with a bit of ally in the way? Or does it have to be directly in the petrol?

What is drawing me towards opto is the LED and sensor could be inside, no ambient light at all then, and just the lobes of the rotor to break the beam and trigger it. Nothing to try and stick in the rotor then.


For a change the mechanical seems easy.
What seems a little difficult is I know no C code, just a little MATLAB... how different can it be   :lol: :bang:

Offline AndreasL

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Re: Flow measuring device
« Reply #10 on: July 28, 2011, 09:40:57 AM »
This is one I support and will follow. Contribute...mmm, If I can that is.  My skills in programming is...slim to say the least.  ::)

But as an Mechanical Design Engineer and in to Racing Cars incl. data loggers etc I have this will to try to make a "information panel" for "the family boat" this winter.
I know my father in law really would appreciate it.

So any information like yours is really worth a lot.  :thumbup:

I have had a small look maybe using a Aurdino, but there may be several other options thats better (Read: EASIER!)?

Offline yorkie_chris

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Re: Flow measuring device
« Reply #11 on: September 11, 2011, 08:51:34 AM »
Arduino seems pretty well supported, my thought was to go with the AVR chip though as the accessory boards and such with arduino setup don't seem necessary for this.

I would advise against putting any sort of display like this on a boat, the numbers will just scare you  :lol:
Friend of mine has a 10m RIB with 400bhp, 150+l/hr is not unusual  :loco: