# Motion sensitive flow control



## Hamer (Oct 5, 2010)

Hey all. I have a situation I need to resolve. I know how to this with a PLC, but as of now, there's no PLC on the machine. 

We have an interlocked infeed/outfeed setup for our chipper. The problem arises when the outfeed chain breaks. The interlock is run through the auxillaries on the affected motor starters. This works great if one of the motors trips the overloads. But if the drive chain or outfeed chain breaks, the motor is still turning and the infeed keeps running, clogging up the chipper and causing all kinds of problems.

What I have in mind is a variation on a PLC controlled setup we have elsewhere on plant. On one of the idler sprockets, we have a piece of keystock welded on the shaft that, when rotating, makes and breaks a prox switch. In the ladder logic, if no motion or pulse is detected, a timer breaks the rung and the motor is stopped, breaking the contacts on the auxillary, breaking the interlock and shutting down the infeed.

I am trying to figure out a way to do this with one or two timed relays and no PLC. On paper, it looks like it would work, but on the bench, it's not functioning like I think it should. Has anyone done something like this with relay logic?


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## MDShunk (Jan 7, 2007)

There are specialized broken belt relays.


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## Hamer (Oct 5, 2010)

Don't happen to have a link do you? I'll look for it on my own too. I know I could put a Micro-800 on it and solve the problem. It's more of a challenge just for me.


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## Splash (Apr 11, 2008)

Hard to troubleshoot without knowing what kind of timing relay you are using. Is the relay triggering with the prox?


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## Hamer (Oct 5, 2010)

We've tried a couple of configurations with OMRON multi time relays. I tried it with a pneumatic timer and almost got what I was looking for. The only problem was: If the idler happened to stop with the relay made (keystock in front of prox switch), there was no way to indicate lack of rotation. That's why I thought I needed two relays.

I think MD has the right idea. This isn't a critical issue ATM. I just like to failsafe everything I can. When something takes me this long to figure out, I just bite the bullet and ask.


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## John Valdes (May 17, 2007)

Are the product transferred to the chipper via a conveyor belt?
Maybe look at the product instead of chain rotation? Chips build on conveyor, photo eye turns off feed? Just an example.
If you are just trying to test yourself, the sky is the limit. If this is an important process, I suggest you look at the big picture. There is more than one way to skin a cat.


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## MDShunk (Jan 7, 2007)

Hamer said:


> Don't happen to have a link do you? I'll look for it on my own too. I know I could put a Micro-800 on it and solve the problem. It's more of a challenge just for me.


Since you already have a prox, all you need now is called a "watchdog relay". Google that. There are a bunch. Some other names for essentially the same relay are tach monitor relay, speed relay, and cycle monitor relay. You may find a better one for your application under one of those names.

http://www.go4b.com/usa/technical-support/technical-papers/slack-and-broken-chain-detector.pdf


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## greenman (Apr 20, 2012)

*Try this*

*Siemens Milltronics MFA-4* Motion Failure Alarm and Speed Sensors*

http://www.lesman.com/unleashd/catalog/belt/bsfm_mfa4.html
or
http://www.gavazzi-automation.com/group.asp


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## JRaef (Mar 23, 2009)

Current sensing relay. Measure the *unloaded* current of the motor, set the CSR slightly higher than that. If the motor starter is ON, but the current is not above that threshold, you must have a broken shft, chain etc. Simple relay logic.


NK Go-No Go Current Switch

Veris Industries same thing (shows prices at under $100).


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## sbrn33 (Mar 15, 2007)

Cheaper to use a little Logo or Zelio than a bunch of timers


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## sparky970 (Mar 19, 2008)

http://ittmc.com/PS10PS20LM.html

We've used these on mag drive pumps


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## Splash (Apr 11, 2008)

Since you already have a pulse I would go with a watchdog relay.


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## Hamer (Oct 5, 2010)

I was familiar with the watchdog concept as far as a PLC goes. Didn't realize there was a real-world unit. Good ideas guys. That's why I ask here. We'll discuss it and make our move. I'll bet they end up wanting me to go with a micrologix controller, but it's good to know I could pull it off with straight up wiring if I wanted to.


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## John (Jan 22, 2007)

Try a Allen Bradley 808 speed sensing switch.I worked in a factory that had miles of conveyor belts and used these to monitor them.


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## Peewee0413 (Oct 18, 2012)

Hamer said:


> Hey all. I have a situation I need to resolve. I know how to this with a PLC, but as of now, there's no PLC on the machine.
> 
> We have an interlocked infeed/outfeed setup for our chipper. The problem arises when the outfeed chain breaks. The interlock is run through the auxillaries on the affected motor starters. This works great if one of the motors trips the overloads. But if the drive chain or outfeed chain breaks, the motor is still turning and the infeed keeps running, clogging up the chipper and causing all kinds of problems.
> 
> ...


are you allowing for errors? like missing a pulse?


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## wendon (Sep 27, 2010)

I've installed a type of motion sensor on some motors that was a self contained unit that mounted next to the motor. There was a little magnet that got tapped into the driven pulley and a sensor mounted on the back side of the shield. I'm not sure of the manufacturer but it worked slick.


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## Hamer (Oct 5, 2010)

We talked about several options. The good news is that I got to read about some stuff I'd never dealt with before. We ended up using an AB Micro810. Found one cheap. Thanks for all the input guys.


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