Simple circuit to indicate rotation has stopped
Simple circuit to indicate rotation has stopped
(OP)
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?
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?





RE: Simple circuit to indicate rotation has stopped
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
RE: Simple circuit to indicate rotation has stopped
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RE: Simple circuit to indicate rotation has stopped
I have no imbedded controller skills, (I don't even know what it means).
This will be for 15 units.
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
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If we learn from our mistakes I'm getting a great education!
RE: Simple circuit to indicate rotation has stopped
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
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
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
RE: Simple circuit to indicate rotation has stopped
Oops, sorry, that's a mechanical answer. :)
RE: Simple circuit to indicate rotation has stopped
http://www.ecelab.com/circuit-miss-pulse-det.htm
Roy
RE: Simple circuit to indicate rotation has stopped
Bill
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"Why not the best?"
Jimmy Carter
RE: Simple circuit to indicate rotation has stopped
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!
RE: Simple circuit to indicate rotation has stopped
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.
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Simple circuit to indicate rotation has stopped
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...
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
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.
RE: Simple circuit to indicate rotation has stopped
h
One thing to consider is that the watchdog must be edge-triggered. Otherwise, if the gear stops on one of the prox. switch targets, a simple 555 reset scheme will be held off indefinitely. The app notes for these parts may have some other insights into possible design issues.
RE: Simple circuit to indicate rotation has stopped
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Simple circuit to indicate rotation has stopped
I have investigated the 555 circuits ( missing pulse detector ) that were mentioned and also looked into hall effect sensors. I would like to use both, but have no experience with actual circuit design.
Terms like when triggered, the output goes low, what does that mean? Would I need a relay at the output to turn on a light of the relay is de-energized?
Then there is the problem one of you mentioned about where or not the gear stopped next to the sensor. Since the repetition stops, will the missing pulse detector not perform as designed?
I think I need to find a "Circuits for Dummies" Book!
RE: Simple circuit to indicate rotation has stopped
Then, there's the issue of latency. How many pulses per second (RPM, whatever) does this device run at? What is the minimum speed under which a 'no rotation' signal must be generated and how soon after it drops below this threshold must a signal be produced?
The behavior I mentioned in a previous post applies to some of the simplest 555 circuits, which are timers that will run to completion if not periodically reset. If the pulse which resets the timer is based on a sensor level (high or low), what happens if the gear stops directly under the sensor, holding the 555 'off' and incapable of generating its output indefinitely? These are all things that have been addressed by designers of things like watchdog circuits. You'll still have to do some soldering, but the application notes will probably cover a case close enough to yours that re-inventing the wheel will be unnecessary.
RE: Simple circuit to indicate rotation has stopped
RE: Simple circuit to indicate rotation has stopped
Nice thing is that one will run on 24VDC and the NPN from the proxy switch can connect directly to the start input. Y?You should just require the proxy sensor, 24VDC power supply and timer to make the circuit. It also has contact outputs which make it easy to use the output.
RE: Simple circuit to indicate rotation has stopped
http
Page 20 shows how to connect the proxy switch.
RE: Simple circuit to indicate rotation has stopped
This looks like any excellent solution, except for the cost. I was hoping to do this for a lot less money, but I don't know how. I design mechanical stuff, and although I can put together some simple electronic parts, I have no idea of how they connect.
I will keep your suggestion in mind, but I am sure the "counters of beans" will shoot it down.
Thanks,
Paul
RE: Simple circuit to indicate rotation has stopped
If you can change to magnets instead of steel in the gear then you could find some cheaper sensors.
RE: Simple circuit to indicate rotation has stopped
In any earlier post I mentioned looking a hall effect sensors, and was thinking of using the Allegro switch on this page: http://w
Based on my very limited knowledge, I thought this would work.
Someone mentioned earlier in the post that there would be a problem if the input stayed high. How do I overcome that? Would that be a problem if I used the timer you mentioned?