Photo Tachometers & Spindle RPM

[elecbob]

Thanks for the many inputs. I ended up getting a Nieko (Asian) photo tach off ebay. I had noticed that the guy on Hoss Machine was using one. It was only $24.95 and free shipping. Comes with a good quantity of reflective tape and a nice fabric case. Seems to be accurate enough. I made a chart of all the different spindle RPM's using the different pulley and back gear combos. Thanks for all the info.
Bob

 

[lens42]

Yes, it's "pretty much" that simple. I don't know if it was this exact tachometer, but I bought one of the Asian cheapy tachs off eBay for about $8 with shipping, and built it into my Maximat lathe. I used a QRD1114 photo transmitter/receiver (Digikey) for the sensor. I also added a comparator to square up the sensor output for the tach input. I'm not sure if that is absolutely needed, but it makes a nice squarewave that I figured would be less susceptible to noise. I hacked up some copper clad with a hobby knife, wired up the the sensor and comparator IC, covered it with heat-shrink tubing and mounted it over my spindle. There's an inch of reflective tape on the spindle. This works very nicely.

One other thing I did is modify the Tach to run off 5V so I could power it from a spare 5V phone wall wart. It's spec'd at 12V, but the whole board runs off a 12V to 5V linear regulator, so I bypassed that and hooked 5V to the regulator output. That also makes the board run cooler, which I cared about since I have it in a closed-up box.

(unrelated - If anyone knows why I can't get rid of that last photo (the 2nd control box picture), I'd like to know. When I try to edit the post, it's not there, but when I preview or save, it shows up. I thought I deleted it)

Has anyone tried one of these?

It sounds as though you hook up a sensor, hook up a power supply and off to the races. Surely it cannot be that simple?

Thanks!

Bob

 

[lens42]

Thanks for posting^. I was just looking at that model and wondered if it would work decent or not. I have a drill press and lathe I would like to hook up.

One thing I forgot to mention is if you plan on panel-mounting the tach without their cheap plastic case, be sure you get one with a circuit board that has mounting holes in the corner. Not all the Chinese eBay tachs have the holes, but some show pictures that do. It only matters if you plan on NOT using their snap-in case and mounting it like it like I did.