Tracking Temperatures via the SMBus

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How-To add more temperature sensors to your computer – Lee Hollis

After downloading the latest version of Motherboard Monitor a few weeks ago I found a link to explaining how to add more temperature sensors to your computer. I just happened to pass this link onto a mate of mine who told me “No worries, I’ll build it, just get me the chip.”

Well, I got it and my mate came up with this:


Built around a Maxim MAX1668MEE, it reads 5 different temperatures via the SMBus using MBM 5.2 or later. The MAX1668MEE has one local sensor and can read up to 4 remote sensors with a documented accuracy of 3 degrees Celsius (mine is accurate to 1 degree). You can find the data sheet HERE.


Building the thing isn’t really too difficult if you’re moderately adept at soldering; however, the chip is small – very small:


The biggest problem living in Australia is getting things. It’s not impossible to get things, just difficult. Take for instance the MAX1668; I found I couldn’t get one unless I ordered a minimum of $300.00. I wasn’t about to do that, so I had to contact a friend in the US to get one for me. I’m sure anyone in the US could contact Maxim and get one.

If you’re not inclined to build your own, Maxim will sell you an evaluation kit built on the MAX1668. However, it’s not cheap – they quoted me $60.00 USD.

Etching the Board

The board layout is pretty simple:


According to, you don’t need the capacitors on c2-c5 or the 200ohm resistor at R1, but I wouldn’t recommend leaving them out unless you are planning on using very long lines on your transistors, due to the chance of errors caused by line noise. You could use veroboard instead of blank PCB, but it’s not going to look as neat or be as small as a printed board. It’s not difficult making your own printed boards – Radio Shack sell kits in the US and Dick Smith Electronics sells them here in Australia.



Lee Hollis

Construction – You Will Need:

  • Double sided tape
  • 4- 2200 pF Capacitors
  • 1- 0.1 uF Capacitor
  • 1- 200 ohm 1/4w Resistor
  • 1- PCB etching kit (at least 50mm x 60mm blank copper PCB)
  • 1- Wire link
  • 4- 2N3904 transistors connected as diodes
  • 4- 400mm lengths of 10x 0.12mm twisted pair wire (You will have to do the twisting yourself, however if you find anyone who sells it please let me know!)
  • 1- 400mm length of 10x 0.12mm 4 core wire (multi-colour hook up wire is what was used for this project)
  • 1- 4way dual In-line/ jumpers
  • 2- Jumper shunts
  • 4- 3pin plug connectors
  • 4- 3pin socket connectors
  • 1- 4pin plug connector
  • 1- 4pin socket connector
  • 1- 5pin socket connector to fit SMBus header (The card shown uses a 6 pin socket with the unused sockets blocked off to prevent an incorrect connection)
  • 1- Maxim MAX1668MEE IC
  • 20″- very fine tinned copper wire (0.12mm)

The chip is placed on the board upside down and stuck on with a bit of double sided tape to hold it in place during construction.

Take a length of tinned wire, solder it to the board, then cut and bend it into position. Solder it to the chip leg by touching fresh solder to the iron and the iron to the wire above the chip leg simultaneously. To do this will require a strong hands-free magnifying glass, a good support for the board and somewhere to rest your soldering iron hand. An upturned bowl and some Blue Tac to hold the board worked fine:


The chip shouldn’t be permanently glued to be board, because that could possibly effect the responsiveness of the local sensor. The tape helps insulate the chip from the board, thus allowing the sensor to adjust to changing temperatures quickly.

Each of the 16 pins measures only 0.25 mm, so it’s almost impossible to solder wires to the pins without connecting the different pins together. However, they can be separated by reheating the solder and dragging a sewing needle between the pins. Everything else is pretty straight forward.


The address settings below are correct for my Abit AT7 MB and for Asus A7V, but I can’t verify any other boards; yours should be the same, though.



Use MBM to check your SMBus before setting the address.

Go to Settings, then to System info and click on SMB dump – it will display your SMB by addresses. Pick an empty one and set the jumpers to that setting. There are only 9 address settings, but since hardly anything uses the SMBus, there really shouldn’t be a problem finding an empty address – most likely all of them will be unused.


Or maybe not, but why take the chance; consult your motherboard manual before installation.

Take care when mounting the board; make sure you don’t place it where it can short out. It might be wise to insulate the back if you plan on screwing it to any metal parts in the case.

I mounted mine using stick-on plastic zip tie holders and stuck it in front of the front intake fan.


(Yep, it’s a mains power fan, all my fans are 240 vac. Never mind the vinyl tape – there’s a proper insulated connector underneath.)

This allows the local sensor to measure the incoming air.



The sensors are pretty good when it comes to measuring air temperatures and they should be OK for most components, like hard disk drives. I’m sure I’ll have no trouble adapting it for use with a water-cooling rig I’ve built –
more on that in the future.

My Thanks to Clive B. for building the card.

Lee Hollis


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