Gang, Looking for links for a fairly good, reliable and accurate revolution (not speed) counter to attach or use on my metal lathe chuck. Reflective tape on the chuck or (less desirable) a magnet on the chuck. I've been looking, but I'm not finding what I think will work. Anybody using something on their lathe that works good? Any good ideas? Help greatly appreciated. Ken Sterling
Winding a coil? If you're not going too high RPM, there are mechanical counters that you can just flip every time something goes by.. my local Chinese guy charges $6 a piece for them. McMaster et al ought to have something similar, probably at >5x the price. Took a lot of b*ggering around to get it to work when we did it.
You could use a magnet and a reed-switch activated electronic counter- some of them are battery powered (throw it away when the battery runs out!) and about $60 a shot. Or use a reflective opto pickup, but you'll have to get it quite close to the reflective tape on the chuck to get it to work reliably.
Omron, probably via Digi-Key. They have reflective optical sensors with built in signal conditioning for the detection end and simple counter display modules that should be able to accept the input from the optical sensor. The lathe chuck is probably pretty reflective, so a wrap of black friction tape first followed by a piece of reflective tape ought to do. Not sure why you need counts, spring or coil winding perhaps?
Spehro, Don't think a mechanical would be good enough. I'd be afraid that it wouldn't catch *every* revolution. The reed switch and magnet would probably work (reaction time quick enough) but I'm not sure *which* electronic counter I need. Thanks Ken
Pete, Black tape sounds like a good idea. What do I need to look for concerning resolution, etc? I'm assuming (I know, not a good idea) that these would transmit some sort of a light source themselves and then pick up the reflection on a sensor?? Thanks. Ken
The battery powered Red Lion Cubs are pretty tough and reliable:
Depending on speed and what you can conveniently mount for a target, an inductive prox, photosensor, reed switch, or variable reluctance sensor would work to trigger the counter. The variable reluctance sensor doesn't need a power source and could pick up a projection on the spindle or chuck. Downside is the target needs to be moving above some minimum speed to trigger the sensor.
digital pedometers are cheap. Not sure how fast they can count. Use a magnet/reed switch to replace the swinging weight. Depending on how fast you want to run it, you might be able to stick it on the chuck. Or put something on the chuck or workpiece to slap the pedometer every revolution. Obviously can't go fast that way.
Resolution shouldn't be an issue if you are just counting revolutions, all of the sensors should be plenty fast for counting one reflective spot per rev.
I used an Omron reflective sensor, something like the Digi-Key OR536 (a part I got as a sample some time ago) as a spindle tach sensor on a mini mill. I made a bracket to aim it at the top locknut on the spindle which has a black oxide finish, and put a square of aluminum tape on it which worked well.
There is quite a variety of Omron reflective logic output sensors available over a wide price range. Something like the OR525 would probably be fine if you can mount it, otherwise something like OR580 might be easier to mount. Just match up the output type with the counter module you select. For a counter, something like the RLC2000 from Digi-Key would probably do the job.
Okay ALL and THANKS SO MUCH for all the suggestion and ideas and links. I've decided that probably the best unit for my application will be the Red Lion Cub 3 model counter and I can "drive" it with a simple magnet and reed switch (which I already have). I have ordered one from Digi-Key tonight (although there was a Cub2 on Ebay which looked a little beat up, but probably would have been fine - I would rather have a new unit). Thanks again to ALL who responded with some fantastic ideas (cheap calculator - never would have thought of that one). Ken Sterling
How many RPM? Electro-mechanical (solenoid driving counter readout from contact closures on a cam-operated switch) is probably fast enough for any speed you are safe using. :-)
If the counter is electronic, and you are using a reed switch actuated by a passing magnet, look for a mercury-wetted reed switch. Otherwise, you will get contact bounce, and the electronic counter can count *every* bounce. :-)
If a mechanical switch (something like a cam-actuated MicroSwitch, take two Dual input NAND gates (7400 TTL at whatever speed and power level you can find. Cross-link the output of one NAND to one input of the other, and vise versa, and use the switch to connect one remaining NAND input to ground in the rest position, and the other to ground in the actuated position. This circuit will latch, so the switch contacts can bounce all they want -- it won't show up on the output (which can be taken from either of the two NAND gate outputs.
If the counter is a solenoid operated Veeder-Root style counter, it won't react quickly enough for the contact bounce to be a problem, so don't worry. :-)