In over my head with electrical.

GA

Currently I don't have any problem, manually firring it to 120 RPM's.

I don't anticipate more then 60 to 100 RPM's.

If it goes faster then that, it will apply a centrifugal brake

Then, if it's just the mechanical switch that's the issue, I recommend an optical switch - either the one I recommended of the one in the post below mine. Although the magnetic sensor will work as well.

I like this solution, This is really close to what I'm looking for. Except I cant use this one, it has a max temp. of 25C. As this will sit outside at an ambient temp. of up to 45C.

No - it's good up to 75C. The 25C number is just how they quote the "typical" performance specs.

GA bhankiii

If you already have a bump on your flywheel and it's metal, you can use an inductive proximity sensor.

Just one thing.

How many "bumps" do you have on your flywheel? If it's just one, you might have problems with balance. The mass of the bump tends to pull the flywheel around with it, causing vibration in the system. If the mass is negligible, this may not be so much of a problem but, if it's possible, I'd put another bump on the other side of the flywheel. You'll have to divide your pulses by two to get the actual rpm but that's easily done.

That is one of my current problems. But I hope most of them are temporary, as it's still small in scale. after I work out a couple of other bugs like the one you pointed out, I will increase the size. And of course I will get a hole new set of bugs.

I knew when I wrote this question, that I was in the right place.

Thanks every one for the great suggestions.

Ill be back with more bugs. I need an exterminator.

How 'bout a small magnet and a hall effect sensor?

How ya been Robin ? When you coming to Worcester?

This is a new one on me what's a hall effect sensor?

A hall effect sensor is a semiconductor device that can measure or detect a magnetic field. Some devices provide an analog output that varies by the strength of the field and other devices are switching type designed to be triggered at a set field strength.

I installed proximity probes on generator shafts as a multi-setpoint speed pickup 30 years ago at speeds in excess of 900 rpm normal operating speed, with detection to 2 times normal speed during a breaker trip.

Can't recall the name of the manufacturer of the package (sensor, multiple relays with individual speed setpoints, power supply).

If your installation is on a generator, be sure not to short out an insulated bearing housing when mounting the prox probe as you will wipe bearings quickly.

The prox switch uses a tape stuck to the shaft, an alternate type of tape has holes in it to multiply the actual shaft speed if too slow for reliable sensing.

The prox probe tip gap to the shaft may be up to 1/10 inch depending upon speed and prox probe sensitivity.

The bump, eccentricity or run-out on the shaft can be a problem for any sensor, if it is you may have to get an adjustable spacer machined to "round-out your shaft" so it runs true to the shaft centerline. Unless this apparent out-of-round is actually a bow in a long shaft ?

The name of the prox probes and relay set-up I preferred was Dymax or similar, I just searched "speed pickup" and there are programmable tachometers, etc that may do what you want.

From the field;

I would get a proximity switch that would "pick up" the high spot after you modifiy it. Or drill a hole and set the prox switch see the lack of metal.

How many RPM's are you at when you loose your ability to "switch"?

Mike

Around 60 to 70 RPM's At that point it just skips across the limit switch

for a cheap hall effect sensor (or proximity switch) to play with, head down to your local bicycle shop or Wal-Mart and look for an 'add on speedometer'. That is what they use.

If you are lucky you might pick one up a good will, a thrift shop, or on freecycle.com or post for a 'old but working' one on Craigs List.

You need to go with an proximity switch from someone like pepperl-fuchs (www.pepperl-fuch.com). I've used their induction switches with optical barriers for years in extremely nasty conditions measuring stroke and rotation in moderate temperatures (up to 50 C) and in high vibration. Never had a failure (until a roughneck knocked one with a hammer - there's never been ANYTHING build a roughneck can't break).

Try this link for a distributor

http://www.wolfautomation.com/Product.aspx?ProductID=22006

You may need to mount a target (or 2 for balance) on you flywheel but these things are pretty awesome.

Thanks a lot I'm a Roughneck. Thats not the kind of encouragement I needed

Still laughing.

I'd go with Philo on the proximity sensor, but all of the possibilties have the drawback that they will need addidional circuitry to operate an electromagnet. (assuming that Ratsstar isn't referring to a relay)

we need more info!

Right on the mark im not looking for a relay.

Hello

Try using a proximity switch instead

Ben

Hey Ratsstar,

you missed my point. All the above ideas will work but, unlike your limit switch which is probably 5A or 10A rated the electronic units are usually only reted at 0.1A to 0.5A so you will need (probably) a relay or other means to "beef up" the output.

regards

chas

To better define what you are trying to accomplish for all the responders,

You want an electrical circuit that will open and close in excess of 100 times per minute but less then _x_ times per minute ?

The approimate current to be switched is ?

Is the device being switched a relay or other inductive device or resistive ?

The voltage being switched is AC or DC ?

You run up against potential mechanical limits, electrical component limits and potentially discharge arc quench time if a really inductive device is switched.

If your switch started to "float" (not follow the cam) at say 90 rpm.

Then try adding a rubber band to the switch arm to increase the tension holding the arm to the cam, understand this will result in higher wear and may only be a temporary solution to "prove the concept" and verify this is the problem. The rubber band also may not live long in an elevated temperature environment.

A spring could also be used but can have problems a rubber band does not.

If you can gradually increase the speed from the known good previous operating speed to where the problem starts you may see something else, a shaft flexing or end float on a shaft causing the cam to move from under the switch arm, the switch arm flexing,...

If the switch has a roller on the end of the arm the high mass versus a tiny rubbing block will limit the speed that the switch will work at.

In any event, try the rubber band to increase the load on the switch arm and then let us know the results ?