Pro/Forums - View Single Post - Procooling's First monthly Electronics Design Corner

Lmandrake · 05-16-2003, 05:36 PM

Although this discussion seems to have abandoned the notion of using one, a flow sensor can be built using parts from a dead fan. I have built several. An example can be found here:

http://www.overclockers.com/tips642/index02.asp

The electronics are pretty straightforward, you just use a magnetic sensitive device called a Hall Sensor that latches "on" when a magnet passes by in one direction and "off" when the magnet comes back...

I have had a "fail-safe" circuit in my rig for a couple of years. If either the water flow stops or a the water block temp gets too high, the circuit trips a relay that leaves the ATX "power good" open until reset. I use the 5v line that is always on for the flow sensor and have a delay timer built in so the system can start with no water flow. However, if there is still no flow after 7 seconds, it shuts down.

Here is a schematic for a delay timer that operates within a certain period after power is turned "on". If you use it to control a relay switching output from the flow sensor, the fact that there is no flow when you first turn on your PC does not matter.

http://ourworld.compuserve.com/homep....htm#delay.gif

My thermal sensor circuit uses a comparator and is very simple. You don't need much when you are worrying about the kind of temperature swing that occurs with a cooling failure.

A schematic is here:

http://www.mitedu.freeserve.co.uk/Ci.../tempalarm.htm

05-16-2003, 05:36 PM	#18
Lmandrake Cooling Neophyte Join Date: Nov 2001 Location: D.C. Posts: 26	Although this discussion seems to have abandoned the notion of using one, a flow sensor can be built using parts from a dead fan. I have built several. An example can be found here: http://www.overclockers.com/tips642/index02.asp The electronics are pretty straightforward, you just use a magnetic sensitive device called a Hall Sensor that latches "on" when a magnet passes by in one direction and "off" when the magnet comes back... I have had a "fail-safe" circuit in my rig for a couple of years. If either the water flow stops or a the water block temp gets too high, the circuit trips a relay that leaves the ATX "power good" open until reset. I use the 5v line that is always on for the flow sensor and have a delay timer built in so the system can start with no water flow. However, if there is still no flow after 7 seconds, it shuts down. Here is a schematic for a delay timer that operates within a certain period after power is turned "on". If you use it to control a relay switching output from the flow sensor, the fact that there is no flow when you first turn on your PC does not matter. http://ourworld.compuserve.com/homep....htm#delay.gif My thermal sensor circuit uses a comparator and is very simple. You don't need much when you are worrying about the kind of temperature swing that occurs with a cooling failure. A schematic is here: http://www.mitedu.freeserve.co.uk/Ci.../tempalarm.htm __________________ The technology is within the reach of even the smallest nuclear power. Last edited by Lmandrake; 05-16-2003 at 05:49 PM.