Inductive Proximity Sensors

[flyingsparks]

I have not ruled out the speed monitor devices the rest of you have suggested, need to do some more research i think! Thanks for the input..

 

[toasty]

I'd go for the tacho suggestion. Just attach a small dc motor to the thing you are monitoring.....
It'll generate enough voltage and current to hold open a suitable relay when it's turning... Use the relay n/c contacts to drive a buzzer or indicator lamp

 

[bernardgreen]

There may be a mechanical way by detecting mechanical overload as the drum jams. Whether it can be used depends on how the motor driving the belt is mounted to the machine.

The motor body is mounted in a way that allow it to rotate by a few degrees against a strong spring. While the mechanical load is below the normal running load the spring holds the motor in the normal position. If the load increases then the reaction of the motor body against the spring increases to the point where the motor body starts to overcome the spring and rotate by a small amount, This small amount being enough to operate a micro switch to shut down the motor.

Alternatively the tension in the belt between motor and drum could be measured by deflecting the belt with an idler wheel on a spring loaded arm. If the drum starts to jam then the increasing tension in that section of the belt being pulled towards the motor will cause the belt to try and straighten itself thus causing the idler wheel arm to pivot against the spring and that can operate a micro-switch.

 

[Alarm]

Will a bouncing combine possibly cause a binding occasionally but not the stoppage being looked for?
Good idea but more false alarms than needed?

 

[Spark123]

I do have a Siemens LOGO plc I think lying around here somewhere.. Could possibly use that. Anyone know of any ladder logic programming software?

Siemens offer their own software and programming lead for the Logo, you may be able to download the software from the internet however without the lead will be useless. I believe it is possible to program via the front panel if it has one, however is a bit of a pain.
I'm not sure wether or not a Logo will be capable of looking at rapidly changing signals anyway tbh.

 

[flyingsparks]

There may be a mechanical way by detecting mechanical overload as the drum jams. Whether it can be used depends on how the motor driving the belt is mounted to the machine.

The motor body is mounted in a way that allow it to rotate by a few degrees against a strong spring. While the mechanical load is below the normal running load the spring holds the motor in the normal position. If the load increases then the reaction of the motor body against the spring increases to the point where the motor body starts to overcome the spring and rotate by a small amount, This small amount being enough to operate a micro switch to shut down the motor.

Alternatively the tension in the belt between motor and drum could be measured by deflecting the belt with an idler wheel on a spring loaded arm. If the drum starts to jam then the increasing tension in that section of the belt being pulled towards the motor will cause the belt to try and straighten itself thus causing the idler wheel arm to pivot against the spring and that can operate a micro-switch.

Its not an electric motor which drives the belt, its driven by a power take off from the engine and gearboxes.

Regarding the LOGO PLC I will look into the software and if it is able to cope with high frequency inputs. The dynamo idea and using a DC motor is OK, but I would be concerned about the fact that if the main pulley which is about 400mm diamater is doing 800 rpm, a small(ish) wheel and motor running on that is going to be doing quite a high rpm and there are more moving parts to replace...

 

[flameport]

The dynamo idea and using a DC motor is OK, but I would be concerned about the fact that if the main pulley which is about 400mm diamater is doing 800 rpm, a small(ish) wheel and motor running on that is going to be doing quite a high rpm and there are more moving parts to replace...

These are not just DC motors, tachogenerators are specifically manufactured for this type of application. This is not a new idea, such things have been around for decades.
Many types can operate at speeds over 10k rpm.

Some here: http://www.transdrive.co.uk/tachogenerators/industrial-tachogenerators/

 

[flyingsparks]

The dynamo idea and using a DC motor is OK, but I would be concerned about the fact that if the main pulley which is about 400mm diamater is doing 800 rpm, a small(ish) wheel and motor running on that is going to be doing quite a high rpm and there are more moving parts to replace...

These are not just DC motors, tachogenerators are specifically manufactured for this type of application. This is not a new idea, such things have been around for decades.
Many types can operate at speeds over 10k rpm.

Some here: http://www.transdrive.co.uk/tachogenerators/industrial-tachogenerators/[/QUOTE]

thanks i will take a look..

 

[bernardgreen]

If the drum is on a shaft that rotates with the drum and the end of that shaft is accessable then the tacho could be mounted in line with the shaft. Drill and tap the the end of the shaft to enable a small diameter extension shaft to be studded into the shaft. Then a flexible bellows coupling or similar from that shaft to the tacho generator's shaft

( some drums will have a stationary shaft and rotate on bearings between the drum and the shaft )