Blackhole Coolant Flow Sensor

Methods of cooling laser tubes

Blackhole Coolant Flow Sensor

Postby iGull » Tue Jan 03, 2012 1:32 pm

Hi All

Thought I'd put up some pix of my simple coolant flow sensor design.

The idea was to have a detector that wasn't inline with the coolant line and couldn't restrict the flow if it jammed up. Bad experience of these things in industry caused me to to design something that worked in the open flow of the system.

The sensor was cut from some scrap 6mm acrylic - a length of 2mm dia stainless rod for the shaft and three 8mm neodymium magnets let into the impeller (the drawing marks the centres, drill them 3mm deep with a bullet drill). Detector is an old hall effect switch (looks like an e-line transistor) - each time a magnet passes, the switch comes on. I initially tried the system with a reed switch, but the reeds I had were non too sensitive - YMMV. Any old hall effect switch like this should work fine - you'll need to rake through your local suppliers catalogue.
One side of the sensor is tapped to receive the three M4 stainless screws with a bit of plastic spacer tube to keep them apart (mine happened to be a scrap bit of outer sleeve from a sullivan pushrod - model a/c pushrod). I did cut acrylic spacers for the first model, but if you cut them from the same sheet, they're going to be the wrong thickness :) The centre hole on the impeller needs to be drilled accurately at 2mm and the inside faces of the outers need to be again drilled partially through to trap the ends of the shaft - the 1mm holes act to allow water into the joints. A couple of wee plastic washers on the shafts will keep the impeller roughly centred - I used old transistor mounting bushes - you want a 'rattling fit' so that the impeller doesn't jam.
The sensor was wired up to a length of three or four core security cable - heatshrunk to the sensor legs, then the whole end dipped in clear model aircraft dope a few times - giving ten mins between 'coats' - to keep the water out. I guess I could have used silicone sealant, but I was in a hurry and silicone is messy - I've used dope a few times before and the method works just fine. The sensor was held into the rectangular hole with a 'popout' of acrylic from something I had been cutting before - I keep a scrap box of all the bits that end up on the crumb tray under the laser cutter - they eventually come in handy for something :D

The output end of the coolant pipe from the laser is simply tywrapped to the sensor assembly and wire so that the pipe is directed at the impeller. The hall effect switch runs from 5V, so you can connect it to any monitoring system - I like a simple approach and just use an LED attached to a resistor - the LED flashes to indicate flow - no fancy litres/min arduino/picaxe, I just want to know that it's rattling round :lol:

The whole assembly is just dunked in your coolant reservoir/bucket/container - if the impeller jams up, it doesn't restrict the coolant flow and won't cause any overheating probs. Of course, you can connect the sensor to anything you like - calibrate the whole gadget too if that's your thing (but in that case, you probably own a fancy Acme Inline Laser Coolant Monitor Detector with dilithium crystal inserts at the correct operating frequency :lol: )

Cheers

Neil

flowsensor1.JPG
Flowsensor 1



flowsensor2.JPG
Flowsensor 2


Flowmeter v2.zip
Flowsensor Cut File
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Re: Blackhole Coolant Flow Sensor

Postby bdring » Tue Jan 03, 2012 3:39 pm

That is an innovative idea. Do you have any video of it running.

It could probably be wired to a 555 missing pulse detector for very go no/go detector.
Bart
"If you didn't build it, you will never own it."
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Re: Blackhole Coolant Flow Sensor

Postby iGull » Tue Jan 03, 2012 3:54 pm

bdring wrote:That is an innovative idea. Do you have any video of it running.

It could probably be wired to a 555 missing pulse detector for very go no/go detector.


Sorry, I tried to get a vid but it's like the black hole of calcutta under my laser (pun intended :D )

It would be quite boring anyway watching an impeller rotating :D

You must be very old Bart - 555 timers are just so 20th century :D I have it wired to an led, but yes, a missing pulse detector and a wee annoying alarm would work well.
I now use picaxe 08's instead of 555 these days - http://www.picaxe.com/- they are ultra cheap (probably cheaper than a 555!) and fully programmable - worth a look - whole range and some ultra fast - very easy to program - much fun to be had too ;)

Cheers

Neil
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Re: Blackhole Coolant Flow Sensor

Postby BenJackson » Tue Jan 03, 2012 4:50 pm

I like this idea!

Might as well glue in an LM34 (or LM35) temperature sensor while you're at it!
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Re: Blackhole Coolant Flow Sensor

Postby mikegrundvig » Tue Jan 03, 2012 5:41 pm

Ha, this is great. I have a large hydroponics system and wanted to get flow sensors on the input and output of the nutrient tanks and was agonizing over how to get a sensor working on 2" PVC without breaking the bank. This works great, I'll just physically put it in-line with the drains so the force of the flow causes it to spin. Very nice and clean, thanks!

BTW: you might want to put this up on Thingverse as well - it's useful stuff for a lot of DIY machines.

-Mike
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Re: Blackhole Coolant Flow Sensor

Postby iGull » Tue Jan 03, 2012 6:27 pm

mikegrundvig wrote:Ha, this is great. I have a large hydroponics system and wanted to get flow sensors on the input and output of the nutrient tanks and was agonizing over how to get a sensor working on 2" PVC without breaking the bank. This works great, I'll just physically put it in-line with the drains so the force of the flow causes it to spin. Very nice and clean, thanks!

BTW: you might want to put this up on Thingverse as well - it's useful stuff for a lot of DIY machines.

-Mike


Yes, that would probably work well - maybe increase the gap/impeller size proportionately?

I may just tidy up the design and put it on thingiverse - I've used a few designs from there, so it would be a minor payback :D

I like Bens idea of adding a temp sensor to the design (although I'm renowned for disliking adding complication :D :D ). I've done a lot of work in the past on factory monitoring systems - more recently using DS18B20 three wire digital temp sensors with picaxe microcontrollers - would be only a four line program in a picaxe to read the sensor and dump it to a serial LCD - and extremely cheap - could incorporate it with my z axis focus system ...

Talking about sensors, I need a wind sensor, we had 100+ MPH winds here this afternoon!

Cheers

Neil
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Re: Blackhole Coolant Flow Sensor

Postby iGull » Tue Jan 03, 2012 8:35 pm

This is for Bart, the dangerous deep sea flow sensor movie :D :D

I had a brainwave and used an LED torch to illuminate the tank (blue LED torch :) )



I have the flow rate turned down low BTW.

Cheers

Neil
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Re: Blackhole Coolant Flow Sensor

Postby iGull » Wed Jan 04, 2012 12:56 pm

I took the advice and put it on Thingiverse ...

http://www.thingiverse.com/thing:15415

Cheers

Neil
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Re: Blackhole Coolant Flow Sensor

Postby mikegrundvig » Wed Jan 04, 2012 3:20 pm

Thanks for making it available- I think that's a classy move personally. With that said, Lasersaur immediately tweet'd this: https://twitter.com/#!/lasersaur/status ... 8326648832
I went ahead and replied to em - hope ya don't mind: https://twitter.com/#!/mikegrundvig/sta ... 0633524224

-Mike
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Re: Blackhole Coolant Flow Sensor

Postby iGull » Wed Jan 04, 2012 5:13 pm

No problem Mike :D

However, while the laser is my own design (not a .2x, but maybe some 'mongrelisation' of many machines) it currently uses Lasersaur firmware and software - they'll tweet you back and send someone round to break your legs :lol: :lol:

I guess we're all one family anyway :D

Cheers

Neil
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