# external Thermal sensor for ASUS Mobo



## PeteC (Dec 21, 2004)

Hi all,

Well last year I had a problems with my P4P800 deluxe bluescreening due to a memory timing problem ( wouldn't run in dual memory mode etc) pleased to say that after those nice people at ASUS replaced the board for me it is now sorted.

Has anyone used the power supply thermal connector on a P4P800 deluxe board to hook up a sensor to go into the PSU to monitor it. Some PSU's have a sensor built in which would connect to this header, mine does not and I was thinking of fitting one, I presume the device needs to be a thermister but they come in several resistance ranges, typically from around 4.7k to over 150k at 25degrees C has anyone had any success in this area or is there a stock sensor available perhaps?


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## clintfan (Sep 4, 2003)

Good question. Don't know if a stock sensor is available. I couldn't easily find one on the web. If Asus sells one it's certainly not obvious ... however they do sell stuff that isn't on their website --like BIOS chips-- but you have to call them to find out about it.

The Winbond chip seems to want one of 3 possible things, but exactly what it wants has already been preprogrammed into the Asus BIOS and we have no idea which of the 3 modes has been programmed for the register bits driving that TRPWR1 port. Whichever way they went, one side of the sensing device is grounded, so that doesn't provide a clue.

If it's been programmed to take a thermistor, the properties are a beta value of 3435K with a resistance of 10K ohms at 25 deg. C.

If instead it's been programmed to use a thermal diode, there's a couple options: the Winbond chip has a bit to switch between thermistor or diode. But if it's in diode mode, then there's a second bit to switch between wither an actual diode, or a 2N3904 transistor with B-C tied together to _act_ as a thermal diode. You might need to chase the signal traces on the mobo to figure out which circuit they've set up, then consult the Winbond datasheet section 5.3.3.2 for more clues.


I think if you want to be successful with this project, I suggest you phone Asus support, and ask if they intended a thermistor or a diode to be attached to this port. The quoted "thermal sensor cable" is definitely not specific- enough information for your needs. From what I hear you might get quicker turnaround --or at least _some_ answer-- if you choose the phone over an email that might get lost in the pileup. Who knows.. they might even sell you a sensor!

Hope this helps,

-clintfan


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## PeteC (Dec 21, 2004)

Thanks for the very detailed and very helpful advice Clintfan, I did a bit of searching yesterday and Asus make (or made) a cable with thermistor for their boards described as a P2T-cable and the spec of this is exactly what you have described, 10k at 25 C with a beta of 3435. I couldn't find a dealer in the UK listing one of these so I have mailed Asus to see if they can help, either point out a dealer or perhaps sell one direct.

It's interesting that the winbond chip can be programmed for either thermister or diode sensing, some Asus boards use thermistors and you would think that logically the mobo manufacturer would stick with one method for compatibility with other products, but i suppose that would be too much to hope for.

In the absence of a response from Asus I think theres a fairly simple way to check how the chip is programmed, a b3435 thermister should have a resistance of 4.16kohms at 50 c so if I put that resistance across the 2 pin connector the bios should report PSU at 50 c, and likewise at 10k should report 25 c. The problem then would be to source the correct thermistor.

thanks again for the advice

-PeteC


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## clintfan (Sep 4, 2003)

> It's interesting that the winbond chip can be programmed for either thermister or diode sensing, some Asus boards use thermistors and you would think that logically the mobo manufacturer would stick with one method for compatibility with other products, but i suppose that would be too much to hope for.


They probably have. The flexibility of the Winbond is because the CPU's use the diode method. A diode is actually embedded in the CPU core of some CPU's. I think for those that aren't, a diode can be located nearby. Anyway by having it able to handle both types of sensors, it makes the chip attractive to mobo builders.





> In the absence of a response from Asus I think theres a fairly simple way to check how the chip is programmed, a b3435 thermister should have a resistance of 4.16kohms at 50 c so if I put that resistance across the 2 pin connector the bios should report PSU at 50 c, and likewise at 10k should report 25 c.


You sound like you're more "up" on this than I am, it's been just over 20 years since I did any work with thermistors. I'm not sure about the 10K, as there is supposed to be another 10K resistor in series with this onboard, but you're probably right.

Good luck, and let us know if you get that part and where...

-clintfan


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## Dusty019 (Feb 12, 2008)

I've been doing some searching for this very same thing. I found something similar to the discontinued Asus P2T Cable:
Cooler Master HSC-U01 Thermal Sensor Cable.
http://www1.coolermaster.com/index....le&PHPSESSID=a2b3c9d85f4c71e336f27dcbf2a00d3a


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