The 'ultimate rev counter' thread...

[irving2008]

Ok, so I got bored at work writing a paper on why we don't need to spend another £100k on overpriced Sun disc arrays (don't go there OK, I dont want to discuss it further :twisted:) so I decided to draw up this...

Its a rev counter with bell n whistles.

In its most basic form it takes pulses from the rev sensor (on the left), and shows revs on the LCD display.

It will also take a PWM input (or a voltage input but I haven't shown that on the diagram) from MACH3 or EMC2 and output a PWM signal for a speed controller. It could also output a 0 - 10v as well but I've not shown that bit. So it can act in 3 modes:
1/ PWM type 1 in, PWM type 2 out
2/ Voltage in, PWM out
3/ PWM in, voltage out

The two preset resistors set the upper and lower bound of the output speed. A commanded speed below the lower bound results in no motion. I've assumed for the moment that MACH3/EMC would control the spindle power relay, but it woudnt be hard to add this here.

Since we know commanded speed and actual speed it would be possible to provide closed loop control, although that requires some interesting calculations. This chip only has 2k of program memory, so might need to go to its bigger brother for that.