57MM DC Spindle

That would be cool. But no, I reach right in there and adjust it. But I have the Hitachi 12mc and the dial is conveniently located up top. Not sure where it is on the other routers.

Still, sometimes spending the money and experimenting is worth it… as long as you remember to temper your regret.

I built a homemade Arduino-based tachometer that will soon permanently mount to my machine. I was able to find a cheap Arduino clone, I nice IR LED/REceiver combo (10 pack), and a tiny, inexpensive OLED display. $12 for the Uno; $2 for the sensor; $10 for a cool readout. I wrote the code yesterday and tested it. Works great. Will mount this weekend. Let me know if you want the details, schematic or code.

I would love to see this device permanently mounted. I might be interested in a similar setup.

Here you go:

Here is the under side. I made the air diverter and dust shoe out of kitchen cutting board (HDPE). The sensor mount is also HDPE and I thought it deserved a little protection under there. The LED light (not necessary but it illuminates the work and makes it easier to see through the clear dust curtain) came from a cheap book light. I used my z-axis limit switch wire to supply five volts to the circuit.

A few things to consider: 1. The wire to the sensor must be shielded. I used a shielded cat 6 cable.
2. The whole thing can be 1/3 the size of mine. You can use the Arduino micro: http://www.amazon.com/OSOYOO-Arduino-ATMEGA328P-Module-Micro-controller/dp/B00UACD13Q/ref=sr_1_4?&ie=UTF8&qid=1440693358&sr=8-4&keywords=arduino+micro

The code is posted elsewhere but let me know if you want it. I went through four revisions to get a stable reading at >15,000 rpms.