Project 4 - Tachometer

Its been over a month since my last post... I did not work much on the others, but I did manage to add another project to my list.

Enter Project 4, the tachometer.  This project was spawned from my father buying a mini milling machine from Grizzly Industrial Inc.  The machine is model G0463 which is a variation of other mini mills on the market.

Grizzly Mini Mill Model G0463

The more expensive mini mill model comes with a number of bells and whistles which may or may not pay for themselves, one of them being an RPM gauge.  After a bit of discussion, I decided to take on the task of making a tachometer to determine the RPM of the spindle.  The range is from 0 to 2000 RPM.  I will probably use a sensor to measure the passing teeth on the drive gear beneath the upper cover... but we'll see how that goes.

Below you can see the current breadboard assembly.  I am using a PIC16F877A for now and will switch to something with less pins when I get the time.  I am also using an old mouse encoder wheel mounted to a motor which I can use to simulate the spindle (bottom right).  The sensor is a simple photogate, which has one LED pointing at a light sensor (all in infrared).

Tachometer Breadboard Set-Up

I bought the following from Sparkfun to display the four digit RPM.

Sparkfun Display Order

I managed to send the numbers via serial communication but was not getting the correct range of RPM... I need to play with the code, the delay_ms(time) function in Sourceboost C may be inaccurate.  I don't have any pictures of that quite yet.

The plan, for now, is to use 1 pin to send the RPM to the display instead of 28 pins.  I did not want the hassle of connecting up each led in each segment and then having to control the mess in the code.  That may happen in a later addition and maybe even if I layout a board for this project.