For my Clarke CMD10 milling machine I wanted to add a tachometer so that I could better judge the appropriate cutting speeds for various materials, rather than doing the whole thing by ear (literally).
The CMD10 has many failings. It's sloppy, the ways are rough, the tool head nods like an amused donkey.
The list goes on. But one of it's great features is it's speed control. A fairly decent quality potentiometer governs the spindle speed from stall speed (60RPM or so) up to a stated 2000 (mine tops out at 1975). Within that range you can pick any speed you like to a fine resolution. This really does feel nice to use since the machinist can simply use their ears to sense the changes in spindle speed. Quite a pleasant way to use the machine. But I like accuracy, so I wanted a tacho to tell me the precise speed of the tool's rotation in real-time.
Why buy a tacho when you can build one? I thought it would be a cool project and there happens to be a convenient spot on top of the machine for a tacho to live. I fired up my pen and paper and wrote some code to do the requisite calculations. Then threw a board together and did a bit more code to drive a 4 digit LED display. Actually this is a fair amount of coding to do but it's a lot of fun to do some serious coding in PASM.
To bring this blog up to date for once (!!!), today I managed to motivate myself to get this build into a state where the RPM sensing and display code is fully operational and made a quick video of it...
https://flic.kr/p/mUsYE2
Next I plan to find a way to add X and Y axis position readings to the display. Watch this space.
Thanks for reading, comments welcome. :)
The CMD10 has many failings. It's sloppy, the ways are rough, the tool head nods like an amused donkey.
The list goes on. But one of it's great features is it's speed control. A fairly decent quality potentiometer governs the spindle speed from stall speed (60RPM or so) up to a stated 2000 (mine tops out at 1975). Within that range you can pick any speed you like to a fine resolution. This really does feel nice to use since the machinist can simply use their ears to sense the changes in spindle speed. Quite a pleasant way to use the machine. But I like accuracy, so I wanted a tacho to tell me the precise speed of the tool's rotation in real-time.
Why buy a tacho when you can build one? I thought it would be a cool project and there happens to be a convenient spot on top of the machine for a tacho to live. I fired up my pen and paper and wrote some code to do the requisite calculations. Then threw a board together and did a bit more code to drive a 4 digit LED display. Actually this is a fair amount of coding to do but it's a lot of fun to do some serious coding in PASM.
To bring this blog up to date for once (!!!), today I managed to motivate myself to get this build into a state where the RPM sensing and display code is fully operational and made a quick video of it...
https://flic.kr/p/mUsYE2
Next I plan to find a way to add X and Y axis position readings to the display. Watch this space.
Thanks for reading, comments welcome. :)