Inexpensive Non Contact Tachometers....??

Just got my Neiko tach. Was excited when it arrived. This looks more like a cheap kit than anything, but it mostly works. The battery springs are in full coil bind and then some. The supplied batteries wouldn't fit. Had to find some other batteries that would fit. The laser spot is not aligned correctly and is internally occluded. The spot is uneven in illumination within the beam and sharply cut off due to the misalignment. The battery compartment screw was installed by Godzilla. Have no idea why it was screwed in so tightly! This photo is overexposed, the illumination is worse than this. Camera is making it look better than it is.
PXL_20210818_174954015.NIGHT.jpg
But, it does seem to work. I cleaned my chuck with alcohol wipes and wrapped a piece of black electrical tape around it, leaving a shiny gap about one beamwidth. It is concerning that if I move the tach a little to the right, the readings are much different. My chuck is still slinging a little oil, so I get a couple of droplets on the tach. Kind of annoying, and undoubtedly not so hot for the "optics".

Trying to decide if I will return it, or open it up and try to fix it. The packaging that this unit came in is totally ineffective against a product drop. It might have left the factory ok, (optically), but there really was nothing to help cushion any common carrier shipping. This is a typical Amazon thing. They probably made a cost tradeoff between shipping damage and good packing and chose shipping damage.
 
Opened it up, well, because. Can't resist a challenge. LED illuminator was bent away from optical axis. Not quite sure how to fix it, to be honest. Not even sure if it matters. Oh I tried a couple of things, but none of the permutations are much better than what I started with. Installing and removing the batteries is a pain. I need to compress the positive buttons to stop this interference fit.

Ok. The gold one is the emitter. The clear LED looking device is actually the photodetector. The emitter is being occluded by the detector base. From the description in Amazon, dated 2015, a person said the detector was mounted on the other side of the board. Not true in 2021. I could lower the detector a little by resoldering the joint, or install on the other side. Problem with doing the other side is I have to bend the leads in the opposite direction. That might cause the lead to break.
PXL_20210818_192806684.jpgPXL_20210818_192934525.jpg
I have a phototransistor (connected as a diode) which might work. First try, I will lower the detector a little. Not very successful. Need to desolder and form the leads to drop it further. Used some low temp solder to make my life a little easier. It will be fine on the detector. The detector is still eclipsing the beam. I'll try it out and see if it is any better or worse. Seriously considering moving the detector to the bottom of the board.
 
For a lathe, mill, or drill, it seems sensible to install a Hall type sensor as a more permanent fixture, with a hands-free readout. I have a variable speed drill press with one of these, and it's pretty nice to have. Under $20 makes sense.

DIGITEN 4 Digital Green LED Tachometer RPM Speed Meter + Hall Proximity Switch Magnet Sensor NPN for Lathe Conveyor Belt: Amazon.com: Industrial & Scientific

DIGITEN 4 Digital Green LED Tachometer RPM Speed Meter + Hall Proximity Switch Magnet Sensor NPN for Lathe Conveyor Belt: Amazon.com: Industrial & Scientific
www.amazon.com
 
You must log in or register to reply here.
Back
Top