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BladeRunner · 11-12-2002, 04:26 AM

Hi guys, It's true most commercial flow meters are either far too expensive or restrict the flow down to a tiny hole. They also mostly work by spinning an impeller which makes a noise. As I was only after a flow "monitor" not a flow "meter" I made this auto shutoff system, works really well using this, (cheapish, £13 UK), flow switch shown below, bought from RS in the UK, which uses the same principal as the proximity switch shown in my previous posting in this topic HERE

Here's my description of how it works:-

Inside the tube it has a small plastic cylinder which sits on the base of the unit positioned in the branch off part. Inside this plastic cylinder is a small magnet. The "cap" at the top of the Y branch has a proximity switch. When the pump is not running the plastic cylinder sits on the base of the unit so the contacts of the proximity switch remain open. When the pump is on the flow pressure makes the cylinder rise up into the branch so causing the proximity switch to close contacts. (there are two versions, 22mm and 15mm), I used the 22mm so it wont cause any overall flow restriction)

The output from this is run to a "pulse Generator" unit which is a small cheap & simple electronic circuit I made, (with much help from others), to mimic a fans sensor output, so I could use the original "Smart Doctor" utility with my Water-cooled Asus GeForce 3, (with the GF3's fan removed, smart doctor would pop up all the time saying the fan was dead, and there was no way to disable it).

Here is an image of the "pulse gen"

It plugs into the CPU fan header on the motherboard. The sensor output from the "pulse gen" is run through the flow switch so when the pump is running the motherboard reads about 3000rpm just as if a fan is plugged into it. If the pump dies or the flow is interrupted by coolant loss, or flow is low etc, the cylinder in the flow switch will drop down and the proximity switch inside will go open circuit cutting the sensor output to the fan header. This will cause the bios to read 0 rpm and instantly shut the PC down if the bios option is set to "shutdown on CPU fan fail".

I've since found there is a slight problem with this on my motherboard, (Abit KX7 333R), in that the bios setting for "shutdown when CPU Fan fail" doesn't actually work, (It is enabled). It's also nothing to do with my "pulse gen system" because even with no fan connected it doesn't shutdown. I'm therefore using "Motherboard Monitor" with "Shutdown now" set to force shutdown in 0 seconds on no CPU fan rotation. This works fine and shuts off the PC within a few seconds if the Pump or flow is stopped. A bit of an ass about face way of doing it, but until I can find out why the bios setting doesn't work it will do.

The flow switches can be found on the UK RS site, (http://www.rswww.com), by typing this code C257076 into the search feature.

You don't have to use a pulse gen, but can just use a fan as long as it can be run from the motherboard CPU fan header. If you are fanless like myself, then here is the circuit diagram for the pulse gen, with components required.

Wire trace colours used mainly just to show where they pass each other but are not joined, (they are only joined with a circle).

more detail on this in the linked topic at the beginning

If you don't need to have a fanless solution the pulse gen unit is not required. It is then very simple to wire up all you need to do is cut one wire and make two wire joins. This very poor sketch should make it clear

This will mean when the pump is creating flow the contacts in the flow switch will be closed so the fan will output it's RPM to the motherboard in the conventional way via the flowswitch. If flow stops, or drops too low, pump dies, coolant loss etc the contacts in the flow switch will open so the fans rpm output will be switched off causing the mobo to read zero rpm just as if the fan had stopped working, (although the fan will still be running).

The only other things you will need are Motherboard monitor (free), and shutdown now which is free for 2 weeks then costs $19 USD, (make sure you buy it because it doesn't tell you it's stopped working it just pops up a window rather than shutting down). At least you'll have two weeks to get it working and decide if it's what you want.

So total cost:-

Fan (I'd assume you had one but $5)
Flow switch $18
shutdown now $19

total $37 usd without fan, plus a few hours work and maybe some tube, tube clamps and reducers.

not much for piece of mind

(if anyone does this, motherboard monitor wont allow a setting of 0 seconds to shutoff on CPU fan fail, lowest is 10 seconds but it's quite easy to edit the inf, ask if you need to know how).

The beauty is it will power your system off in the correct way if you are not around in event of a failure, so saving your data. If I were running a high watt TEC I'd probably make the system just power off the PSU instantly to be safe.

11-12-2002, 04:26 AM	#19
BladeRunner Cooling Savant Join Date: Jul 2001 Location: Chesterfield Uk Posts: 459	Hi guys, It's true most commercial flow meters are either far too expensive or restrict the flow down to a tiny hole. They also mostly work by spinning an impeller which makes a noise. As I was only after a flow "monitor" not a flow "meter" I made this auto shutoff system, works really well using this, (cheapish, £13 UK), flow switch shown below, bought from RS in the UK, which uses the same principal as the proximity switch shown in my previous posting in this topic HERE Here's my description of how it works:- Inside the tube it has a small plastic cylinder which sits on the base of the unit positioned in the branch off part. Inside this plastic cylinder is a small magnet. The "cap" at the top of the Y branch has a proximity switch. When the pump is not running the plastic cylinder sits on the base of the unit so the contacts of the proximity switch remain open. When the pump is on the flow pressure makes the cylinder rise up into the branch so causing the proximity switch to close contacts. (there are two versions, 22mm and 15mm), I used the 22mm so it wont cause any overall flow restriction) The output from this is run to a "pulse Generator" unit which is a small cheap & simple electronic circuit I made, (with much help from others), to mimic a fans sensor output, so I could use the original "Smart Doctor" utility with my Water-cooled Asus GeForce 3, (with the GF3's fan removed, smart doctor would pop up all the time saying the fan was dead, and there was no way to disable it). Here is an image of the "pulse gen" It plugs into the CPU fan header on the motherboard. The sensor output from the "pulse gen" is run through the flow switch so when the pump is running the motherboard reads about 3000rpm just as if a fan is plugged into it. If the pump dies or the flow is interrupted by coolant loss, or flow is low etc, the cylinder in the flow switch will drop down and the proximity switch inside will go open circuit cutting the sensor output to the fan header. This will cause the bios to read 0 rpm and instantly shut the PC down if the bios option is set to "shutdown on CPU fan fail". I've since found there is a slight problem with this on my motherboard, (Abit KX7 333R), in that the bios setting for "shutdown when CPU Fan fail" doesn't actually work, (It is enabled). It's also nothing to do with my "pulse gen system" because even with no fan connected it doesn't shutdown. I'm therefore using "Motherboard Monitor" with "Shutdown now" set to force shutdown in 0 seconds on no CPU fan rotation. This works fine and shuts off the PC within a few seconds if the Pump or flow is stopped. A bit of an ass about face way of doing it, but until I can find out why the bios setting doesn't work it will do. The flow switches can be found on the UK RS site, (http://www.rswww.com), by typing this code C257076 into the search feature. You don't have to use a pulse gen, but can just use a fan as long as it can be run from the motherboard CPU fan header. If you are fanless like myself, then here is the circuit diagram for the pulse gen, with components required. Wire trace colours used mainly just to show where they pass each other but are not joined, (they are only joined with a circle). more detail on this in the linked topic at the beginning If you don't need to have a fanless solution the pulse gen unit is not required. It is then very simple to wire up all you need to do is cut one wire and make two wire joins. This very poor sketch should make it clear This will mean when the pump is creating flow the contacts in the flow switch will be closed so the fan will output it's RPM to the motherboard in the conventional way via the flowswitch. If flow stops, or drops too low, pump dies, coolant loss etc the contacts in the flow switch will open so the fans rpm output will be switched off causing the mobo to read zero rpm just as if the fan had stopped working, (although the fan will still be running). The only other things you will need are Motherboard monitor (free), and shutdown now which is free for 2 weeks then costs $19 USD, (make sure you buy it because it doesn't tell you it's stopped working it just pops up a window rather than shutting down). At least you'll have two weeks to get it working and decide if it's what you want. So total cost:- Fan (I'd assume you had one but $5) Flow switch $18 shutdown now $19 total $37 usd without fan, plus a few hours work and maybe some tube, tube clamps and reducers. not much for piece of mind (if anyone does this, motherboard monitor wont allow a setting of 0 seconds to shutoff on CPU fan fail, lowest is 10 seconds but it's quite easy to edit the inf, ask if you need to know how). The beauty is it will power your system off in the correct way if you are not around in event of a failure, so saving your data. If I were running a high watt TEC I'd probably make the system just power off the PSU instantly to be safe. __________________ Zero Fan Zone Last edited by BladeRunner; 06-23-2005 at 04:27 PM.