Simple circuit to indicate rotation has stopped 1

[PRW]

I need a simple circuit that will indicate when a gear has stopped rotatong. This is a polypropylene gear that has one or more short metal rods imbedded in it.

In the past I have used the metal with a proximity switch to count the gear speed by an output to a PLC.

On the current project, there will be no output to a PLC, everything will be self contained. So I need a circuit that would run on 12 VDC and light a LED or sound a horn when the gear stopped.

Any ideas?

 

[itsmoked]

There are many ways to do this. And they are all over the place on effort and cost.

Are you up for circuit boards?
Have you got embedded controller skills?
Is this a one-off or for many?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[electricpete]

centrifugal switch is one option

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[PRW]

Actually simple and cheap.

I have no imbedded controller skills, (I don't even know what it means).

This will be for 15 units.

 

[PRW]

The gear moves too slow for a centrifugal switch, but good idea.

 

[ScottyUK]

Timer continuously reset by a pulse from the rotating wheel? Wheel stops, timer runs to end of period, indication triggered. Should be able to build that from off-the-shelf control components.


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If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

Well that precludes something pricey and off-the-shelf.

I can find nothing on a brief web search.

All the remaining solutions, I can think of, are too technical or evolved to ever get across a thread.

I'd use a hall-effect sensor and microcontroller to monitor it and provide the filtering and timing desired to provide your signal. But like all these things once you bother with a micro there are often many other thing you can toss on it that makes the systems better with only minor incremental cost increases.

Then you have the board shape. Sometimes you want a strange shape to fit amongst the gears or in the surrounding spaces.

You also want the mounting of the board to utilize existing screws or available mounting holes.

Maybe you should hunt up an engineer to design these for you and get a quote.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

Assuming you can arrange things so that the system provides rotation output pulses of some sort, then the good old fashioned 555 timer chip can be made to work as a 'missing pulse detector'.

 

[Comcokid]

ScottyUK hit upon my first thought. Since you already had a pulse-type speed sensor, just connect the speed sensor into what is sometimes called a "missing pulse detector", or some other type of pulse detector circuit. This type of circuit is frequently made from 555-type timer chips or from 4538B or similar monostable multivibrator ICs.

 

[itsmoked]

Why do you say he, "has a pulse-type speed sensor"??
I don't see where he said that.(?)

Off-the-shelf prox sensors are not inexpensive and he needs fifteen..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[btrueblood]

A weighted & sprung lever attached to a micro-switch, driven by a cam.

Oops, sorry, that's a mechanical answer.

 

[roydm]

Heres what Comcokid was talking about, use your proximity switch to reset the timer

http://www.ecelab.com/circuit-miss-pulse-det.htm

Roy

 

[waross]

Allen Bradley used to make nice zero speed switches but they were big and pricey.

Bill
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"Why not the best?"
Jimmy Carter

 

[ScottyUK]

That describes Allen Bradley perfectly!

roy & ComcoKid: yes, we're thinking on the same lines. Rather than a roll-yer-own timer circuit there are plenty inexpensive ones which are designed for DIN rail mounting which would avoid getting involved in making boards and the like. I hesitate to suggest anything like Veroboard (stripboard) because I really don't like the stuff, even for a simple circuit like that 555 example.


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If we learn from our mistakes I'm getting a great education!

 

[Comcokid]

I don't work with DIN rail or similar industrial control components, but I'm sure there are 'equivalents' to the circuits I described.

I assume the control in it's PLC version is a pulse-type pickup since it consist of metal rods in a plastic gear sensed by a proximity pickup.

I suggest looking for a time-delay relay/control module with a reset input. Connect the proximity pickup to the reset input. If the delay module does not get a pulse on the reset input (speed=0) then after a quick delay, the module will output a signal indicating that there is no rotation. This is the module equivalent to the missing pulse/monostable circuit I suggested earlier.

 

[melghazaly]

you can weld a small gear to the rotating gear then we can couple it by a chain to another gearbox which rotates a potentiometer that gives a signal to a comparator which determine if there's no signal (gear stopped)

 

[MacGyverS2000]

you can weld a small gear to the rotating gear then we can couple it by a chain to another gearbox which rotates a potentiometer that gives a signal to a comparator which determine if there's no signal (gear stopped)

Isn't that going around your elbow to get to your rear end?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[sisif]

Two circuits are parts of the solution:
1 - a movement/rotation sensor;
2 - a retriggerable timer/monostable.

For the first circuit I'd use either one of this:
- hall sensor; with a small magnet attached/glued to one of the rods
- optical sensor:
- reflective sensor - and you need to glue a piece of reflective foil (like the one used to pack chocolate) on the top of the rod, or
- photo interrupter - with a small piece of opaque foil (metal sheet?) attached to the rod...

For the second circuit I'd go with the good old 555 configured as a retriggerable monostable. I prefer this over the 4528/4538 for reliability, availability and output capabilities.
The whole thing will cost under $5 and, while still demanding basic electronic skills, you don't have to program anything in assembler, C# or other .NET horrors. I know there are many here that would happily replace the 555 (or even a resistor!) with anything from a microcontroller to a mainframe computer, just because is close to their hearts, but is really not the case here...

 

[VEBill]

Although they're not explicitly mentioned, there are probably other bits of hardware that are also rotating. It's safe to assume that the gear in question isn't rotating all by itself.

 

[OperaHouse]

If there is an AC or DC motor involved, that signal can be fed into an op amp. Any voltage and a relay closes. Op amp input can be protected by back to back diodes and a several hundred K resistor.

Even a missing pulse detector can be made with an op amp. Any input signal charges a cap with a long discharge. A second op amp switches when the voltage on the cap goes near zero. A neophyte may have more luck with an op amp than a 555.