I wanted to make a turns counter for my drill press. I have it set for 330 RPMs or about 6 cycles per second. It doesn't work. Unreliable counting. My high point is (switch closure time) about 1/12 of the rotation, I wonder if I did a 50/50 duty cycle if it would be better.
Or, is expecting the switch to operate at 6Hz just to fast for a standard microswitch?
Mikek
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** Try using a reed switch with a small permanent magnet, magnet rotating switch fixed.Many cassette decks used such an arrangement as a tape movement sensor.
... Phil
Why not use a hall-effect instead? Or laser and photo-diode with a small mirror stuck to the side of the quill? I don't see a microswitch as being suitable for this application.
That's sounds good, if I can find my reed switches. We had a hurricane
11 months ago and all my supplies got reshuffled. Pain in the ass committing the position of everything back into a new memory.Mikek
I have a Root Veeder counter all it needs is a pulse, I wanted the project to be counting the turns on a coil, not developing a circuit to make a pulse to drive the counter. Just trying to keep it simple, until I buy a lathe. Mikek
6 Hz should be OK at 50% duty cycle.
Are you debouncing the closure?
Not yet, I'm hoping there is a bit of debounce caused by the electro/mechanics of the counter. It draws 3/4 amp at 12 volts, I can do plenty of fast wire touches without it counting,it does give a nice counter EMF. It won't count until the voltage reaches 6.2 volts. I'll put in a search tomorrow for my reed switches.
Mikek
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** Bet JL has never tried it.I know a reed switch will easily do the job far better.
But I'm not a "designer" . ...
.... Phil
Reed switches won't play nice with 3/4 amp, though. A one-shot for debounce, into a solid state counter like this might be the easiest, and would probably work with the microswitch. It only needs a button cell for power.
counter with Hall sensor and a little magnet
17 bucks---------------
** Nonsense, 12V at 750ma is a piece of cake.Small ones are typically rated at 1 amp and 200V for millions of cycles at up to 100Hz.
Larger types are rated at 250V and 5 amps.
.... Phil
Whether you can mount a magnet on the drill press and whether it has enough time over the switch to make it work might be a question though.
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** If the OP can mount a suitable cam he can also mount a small magnet.Now: The OP's drill turns at up to 300rpm or 166mS per rev.
Operate time for a reed switch is about 2.5mS or 1.5% of a rev.
Betcha it will work just fine.
... Phil
How are you doing the counting?
Sylvia.
Use something made for the job. These come in different counts per turn, and are rated up to 5000 RPM. They run on DC and can be used to count turns, show direction or show the shaft position.
Encoder-360P-R-Incremental-Rotary-Encoder-360p-r-AB-phase-encoder-6mm-Shaft
Dana ponedjeljak, 16. rujna 2019. u 01:45:07 UTC+2, korisnik amdx napisao je:
You can use an inductive sensor instead of a mechanical switch. Inductive sensor has approximately few kHz switching frequency.
** Nice unit but overkill.
The op only wants to count turns cos he is winding inductors. His mechanical counter is fine, it just needs a one cycle per rev switch to drive it.
.... Phil
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** The reference I found suggests 1 cycle per second is the norm used in mechanical life testing of such switches. 6Hz seems very high.But as I posted earlier, reed relays can do it very easily.
.... Phil
Reflective strip of tape and an optical proximity sensor.
I had a small electomechanical counter that was fine with the sub 10ms pulses that I got from a half-wave rectifier,
It must be that your microswitch is too slow. perhaps you can arrange for the counter's drive current to pass through some moving part of the drill.
With a lathe would you use the lead screw as a counter, or do you have some other strategy in mind?
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