Frankenmouse: Kensington Thinking Mouse with USB, scroll wheel, and optical sensor

The Kensington Thinking Mouse is, in my experience, the best mouse ever made, with a comfortable shape and plenty of programmable buttons. Unfortunately, time has passed it by. A modern pro mouse requires a scroll wheel, an optical sensor, and a USB connector. Kensington now only uses the Thinking Mouse's form factor on one- two-button mice, clearly not enough for those of us who have known the power of four buttons.

While searching for a USB replacement for my beloved but obsolete Thinking Mouse, I tried Kensington's Mouse-in-a-box Optical Pro. This is a terrible mouse - too big for my hands, with flimsy, ill-positioned buttons - but the internal circuit board and switch positions are similar to those of the Thinking Mouse. With the aid of a soldering iron and liberal use of a Dremel tool, I built the Frankenmouse: the hardware of a Mouse-in-a-box Optical Pro transplanted into a Thinking Mouse case.

Top view   |   Side view   |   Bottom view


Only the plastic shell for the Thinking Mouse will be used. Save a few bucks by buying the PS/2 model, and leave the rarer ADB version for users of beige Macs. The PS/2 version is about $10 on eBay.

The Mouse-in-a-box Optical Pro is no longer sold by Kensington, but can usually be found on eBay for about $10. I don't whether any other Kensington mice will work well.

There appear to be at least two revisions of the Optical Pro, with slightly different internal circuitry and plastics. I have successfully built a Frankenmouse with both versions.


0. Disclaimer

This worked for me, twice. It may not work for you. It is not recommended or supported by Kensington, and will certainly void your warranty. If something goes wrong, you could break: two perfectly good mice, your computer, your tools, yourself, and anything that gets close to your soldering iron or Dremel tool. Don't try this at home. Void where prohibited. For entertainment purposes only. Ask your mom or dad for help first.

1. Dismantle

Taking stuff apart is always the best part.

2. Rearrange switches

The four switches of the Optical Pro's four buttons need some rearrangement in order to work with the Thinking Mouse's shell. Switch wiring

3. Reshape the circuit board

The Optical Pro's two-part circuit board is too wide and too long to fit inside the Thinking Mouse. A Dremel tool and soldering iron can solve that problem. Finished board   |   Diagram of areas cut from board

4. Reshape the inside of the shell

The inside of the Thinking Mouse's shell needs to be expanded slightly to make room for the new circuit board and its optical sensor. Circuit board in place

5. Position optics

The optical plate needs to be positioned at the proper height for the optical tracking to work. The existing hole for the mouse ball is in the wrong place, so a new hole needs to be cut for the optics.

6. Make room for the scroll wheel

The original Thinking Mouse has neither a scroll wheel nor a hole for one. The new mouse needs both.

7. Reattach switches

The two extra buttons on the Thinking Mouse separate the power users from the newbies. Attach the two switches under the front two buttons and feel your computing skills instantly improve.

8. Enjoy

Your new and improved mouse is complete. Download some drivers from Kensington or USB Overdrive and sell your USB-ADB adapter on eBay.

Frankenmouse   |   top view   |   side view   |   bottom view   |   switch wiring   |   circuit board   |   board cut diagram   |   board in place
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