Hardware protection against water pump failure (Thermal Switch)

[GigaFrog]

If you have a water cooled pelt, you know what will happen if the pump dies and you are away: peltier, water block, and CPU will fry, plus possibly motherboard and videocard.

How to avoid this?
A software protection can be set to turn off the PC if the CPU exceeds a given tmperature. The problem is that the PC is likely to crash before the software protection triggers. You can always back off the CPU clock, but then, what is the point of having a pelt?

The other solution is a hardware protection that will shut down the PC if the water block overheats. I implemented this solution in my computer, and it works great. I use a thermal switch found at MECI.com, part number 580-0203. The thermal switch is connected to the PS_OK signal from the PSU. If the temp of the water block exceeds 57°C, the thermal switch de-activates the PS_OK signal, which will result by an immediate shut down.

I tested it by applying a soldering iron against the thermal switch, and it worked almost immediatly.

Hope this will help someone (it helped me!).

Bye.

[GigaFrog]

???

[AL666]

I think it's a great idea, i wanna try it...

I also wanna do a similar mod to the DigitalDoc5... any ideas?

[ 12-16-2001: Message edited by: AL666 ]

[Joe]

have you read CK42's device? it does what you are talking about for the most part.
http://www.procooling.com/articles/html/cpu_overtemp_power_shutdown_ho.shtml

[GigaFrog]

This is way more complex than what I am using.

Part needed in my solution: 1 thermal switch.
Cost: 75c (yes, $0.75)
Labor: cutting a PSU wire (green PS_OK wire) and soldering its two ends to the thermal switch.
Time required: ~15mn

No PCB, no thermistor, no relay.

Here is a diagram: http://www.geocities.com/alochin/temp/ThermalSwitch.gif

The only drawback of this system: it checks the temp of the waterblock (or heatsink), not the temp of the CPU. It is intended to protect against water pump failure.

[GigaFrog]

Note: to make work the above link, you have to copy-paste the address in the address bar of your browser.

[BrianW]

hey frog i was wondering.... Does that thermal switch have to be connected to the heat source or does it use a thermistor conected to a wire?

Could you show some pics of it installes in ur system?

Thanks.

[GigaFrog]

Yea, I will show some pics, when I will have a digital camera.
Should come in ... about 2 weeks.

[GigaFrog]

It does not use any additional component. It is a bimetal switch that react to temperature. It must be applied to the heat source, in my case, the water block.

[BrianW]

That sucks...

Looks like i'll have to go the other route.

[Brad]

think of it as a normal SPST switch

just have it on the side of a waterblock or something, buy one of the appropriate temp, as soon as it gets to XX C then it turns off.

[GigaFrog]

Exactly.
I put it between the top of the water block and the hold down clamp. It is pressed against the block by the clamp.
As soon as I have a digicam, I'll post pics.

[jaydee]

Good idea!!! I was thinking about a flow switch. If the pump dies the flow would stop and the switch would turn off shutting the comp dowm. Tghe problem is finding a switch capable of doing that without disrupting the water flow. Your idea is better.

[Brad]

so, apart from applying a soldering iron to it, have you done any actual tests of it in a computer?

[GigaFrog]

It is installed in my comp since about 3 months.
When I applied the soldering iron, the thermal switch was connected to the system, and the computer shut down as soon as the iron got warm.
I think it is enough to proof the functionnality of the design.

[dax]

you could prolly do the same with this thermal cutoff component, although i think you can't reuse them if they go over their temp http://www.velleman.be/Product.asp?lan=1&id=346171 those should be pretty cheap too and can handle like 10A through them, enough for a poweron wire

[GigaFrog]

The above link did not work for me.

The PS_OK wire carries very low current, it is a high impedance signal.
You can use any kind of thermal cut-off, as long as you connect them to the PS_OK signal, and they open at the right temperature.

When I will have my peltier installed, I will make the test of shutting down the water pump while the system is runing (scarry test!).

[Brad]

I still think that the thermal trip diode under the core linked to the ps_ok signal is by far the easiest way.

[GigaFrog]

Thermal trip diode?
You mean this solution:
http://www.procooling.com/articles/html/cpu_overtemp_power_shutdown_ho.shtml

I don't get it !!!!
It require you to build an additional PCB. Not that it is a bad solution, it is actually more efficient because it really measure the temp of the CPU, but it is IMO "by far" more complex that what I am using! Come on! An additional PCB, a relay, and a thermistor to put under the CPU, that's not really easy. Let stay realistic!

Pro-cooling's solution is the most efficient solution. But if you don't want to go through the design of a PCB, my solution is by far easier.

Unless you are talking about something else that ProC's solution, I really don't get your statement.
I don't see what can be "by far easier" that my solution ???

This statement really makes no sense to me.

If you really have a solution by far easier that mine, tell it now, and I will apply it right away.

One very important thing in safety system is to make them simple, so that they don't fail. A safety system that fails will not tell that it failed, you will realize it when you will really have a failure, and see that nothing reacted to protect your hardware. The other failure mode of a safety system is generating false alarms, extremely anoying. I want none of that. Thats why I eliminate safety systems that include a PCB, or even more unreliable, software based.

[Brad]

I know, your solution doesn't require any real electrical knowledge or soldering ability.

your solution is much much better

[LiquidCool]

I didnt look at the switch, but is it small enough to sit under the cpu? Between the mobo and bottom of the cpu inside the socket?

[Brad]

10mm x 4.3mm but it has a 1mm thick wire coming out of each end.

if would be possible, but barely

[LiquidCool]

hmmmm ideas.... Artic silver adhesive and a soldering iron :)

[Brad]

yes it should sit quite happily underneath the core, and could be easily integrated into the ps_ok line