RPM counter that stops machine after 10 cycles

[privas]

I have a machine that twist metal square tubes. It makes a spiral turns into the tubes to make them more decorative. Problem is that I have to count the turns myself and then manually turn off the machine. I would like to make or buy a device that would turn off the machine after 10 turns. The machine completes 14 turns in about 90 seconds. The machine operates on 110 volts and has a basic on/off switch.

Any ideas or suggestions?

[gogo2520]

        hello privas
  A rpm counter could be made with a ir led and ir detector. Using a 4017 as a counter and some kind of relay. BUT the thing is SAFETY the Power switch would have to be manualy shut off befor unloading the machine. I don't know what your setup looks like but if you go automatic I would sugest haveing  a cage around it with a door with some kind of cutoff switch to kill the power when its open.
      You could get more elaborate and drop the 4017 counter and use a microcontroller with a count down timer that could be set at any amount of turns you wanted. The relay is no problem, a simple circuit between the mcu and the realy would be easy. And maybe a triger setup for the door latch to reset the counter.
                                              have fun
                                                gogo

[ante]

Hi privas,

If you are using a lathe which has a “clutch” you might want to release the clutch at the right moment instead of switching of the power? This is a safer way to work this if possible.

[privas]

I like the idea. How do I make it. I have a very limited knowledge of electronics.
I know resistor, capacitors, diodes, relays, different voltages, ac, dc, amps but I can't design anything.

1) do you have a model number for the ir led and ir detector from a store like radio shack or some other company that you deal with?
2) what is a 4017 counter? Where can I get one
3) can you sketch something for me, showing how everything is suppose to be wired.
4) the machine is just a very slowing turning more with lots of torque. it has a chuck with a 12" diameter. I imagine that the ir led would go attached to the chuck and the ir detector next to the spinning chuck. Now how do I wire the rest?

[privas]

I like the switch and finger idea better because the work enviroment is dirty and hazardous. So once the finger hits the switch ten times the machine would turn off. The programmable counter would switch the relay from a normally closed position to a normally open position after the set number of turns has been reached. Then it should reset itself or have a reset button. Can you please make a simple sketch so that I can better understand how to wire everything correctly? Please list components needed.

[awright]

Two ideas.

1)  This is a classical application for a Predetermining Counter.  Google "Predetermining Counter" and you will come up with dozens of manufacturers.  This is the bulletproof approach used in industry for this type of application.  You set the dials for whatever count you want.  Press reset to prepare for counting.  When the count reaches zero you get a contact closure or opening that controls a power relay.  Many coil voltages are available to actuate each count, but line voltage would be simplest.  You have to mechanically rig up a microswitch to produce a pulse for eash rotation.

2)  Since you don't have to deal with a lot of differing situations and things are happening pretty slowly, a cheap and dirty method of stopping the machine at 10 counts would be to have a piece of very flexible, small diameter cable or nylon cord that winds up on the workpiece as it turns and activates a switch when the proper length of cord has been wound up on the workpiece.  Perhaps not very elegant or precise, but probably more than adequate to get your desired number of twists.  The cord could pull two contacts apart, pull out an insulating block holding two contacts together, pull out a conductive block maintaining conduction between two contacts, pull on the lever of an industrial limit switch, etc., etc.  You would just have to be sure that any exposed voltages on contacts were safe and that there was sufficient overshoot available on the switch that damage would not be done as the machine coasted down.  But, I imagine that your twisting machine doesn't do much coasting after power is cut.  Your contacts would control a power relay controlling the motor.

awright