Remote control of a PLC-controlled machine

[technolog]

My boss has come up with the idea of renting machines and charging on a per use / per hour basis, so I'm looking into it - just getting my feet wet.

We want a PLC that has the ability to connect to the customer's wi-fi and allows us to remotely see the machine usage and stop it from functioning if bills are unpaid. The I/O count will likely be minimal. We're at the early planning stages but <= 8 discrete ins, <= 4 discrete outputs, <= 4 analog 4-20mA inputs, <= 2 analog outputs.

We would want to operate a fan motor via a VFD and would like the PLC/VFD control to be over a comms bus, preferably Ethernet/IP implicit messaging, that is simple to set up and use (like the Allen-Bradley implicit messaging that I've used previously). My boss has stated an aversion to AB for this particular project - I'm suspecting it's based on perceived cost. He's hoping there's something "cheap & cheerful" in the Automation Direct range. Has anyone used one of their PLC/VFDs in such a fashion? How did it compare with AB?

Does anyone have any insight or suggestions on system architecture?

 

[Locodios]

A quick cheap solution is to use a Automation Direct PLC (DL06) with and Ethernet Module, AO module, and AI module. The base has the DI and DO portion covered. Use the serial port for Modbus communication to your choice of VFD drive and use the Ethernet port with converter to connect to Wifi. Per the functionality for renting, I have used a running clock to verify comms to a server and permissive bit to be able to run. I use to run remote pump stations in Texas like this but we utilized AB and GE PLCs but still over Modbus.

 

[OkiePC]

Stridelinx VPN Routers can allow remote access to PLCs and HMIs. They have wired, wireles and 4G versions. They're simple to set up, secure, and reliable.

Click PLUS PLCs are a huge step up from a DL06 and pushing right up against the Micrologix 1400 capability, but they do lack an LCD and the software is less polished than RSLogix 500.

Some models of the Click PLUS have a wifi port that can connect to a wireless access point, but I have not used that feature. We use a lot of them with all the ports so we can control drives via RS485, connect to serial radios via RS232 and the Ethernet to each other and to HMIs.

I have some controlling Yaskawa VFDs and one or two controlling ABB drives via RS485. Not as slick as Ethernet IP with add on profiles, but functionally it is just fine for water pumping systems that I work with. They speak Modbus natively on all the ports and the instruction set is simple, but plenty flexible for most things. Best of all, there is floating point math with a MATH block (like A/B CPT) and no need to deal with BCD like you do with a DL05/06. The analog I/O is solid too, with card configurable scaling.

 

[Locodios]

I agree with OkiePC. The Click PLC's are a better way to go if you can get them. I have used them as a Slave device but not on Wifi or as a Master.

 

[James Mcquade]

the issue i see is how to lock the plc's the customer cannot buy the software and modify your usage data and yet be able to connect to their wifi.
james

 

[JaxGTO]

You may want your lawyers to go over that method. I was told once by a lawyer that making a machine quit operating at a certain time was considered sabotage.

 

[plvlce]

You may want your lawyers to go over that method. I was told once by a lawyer that making a machine quit operating at a certain time was considered sabotage.

I very much doubt your lawyer was discussing machine rental. It's not the customer's machine here.

If someone contracts to use a machine for a certain length of time and it stops working after that they really don't have any grounds for complaint.

There's issues if it stops working before the specified duration is up, but that should be covered in the contract same as if it breaks down for other reasons.

Although yes the lawyers should be involved, not particularly because of this issue but because you are writing a contract at all.

 

[I_Automation]

I very much doubt your lawyer was discussing machine rental. It's not the customer's machine here.

If someone contracts to use a machine for a certain length of time and it stops working after that....

As long as it's clearly stated in writing then the machine can be shut down, whether it's a rental or purchased on terms.


There was even a used car dealership in the Detroit area that sold cars to people with bad credit - but the payment had to be made in person at the dealership every Friday before 5:00pm so the dealership could relicense the timed interlock they put on the car to allow it to run for another week. Miss a 5:00 payment and the car shut off and had to be towed in to be reset.


The only problem that ended in a lawsuit was it was programmed for exactly 5:00pm on Friday regardless of what the car was doing. In this case the car was doing 70 down the freeway at 5:00 and caused a nice crashsite. They were ordered to rewire and reprogram them all to be that the car could not be started after 5:00 and had to keep running if on at 4:59:59.

 

[cardosocea]

The only problem that ended in a lawsuit was it was programmed for exactly 5:00pm on Friday regardless of what the car was doing. In this case the car was doing 70 down the freeway at 5:00 and caused a nice crashsite. They were ordered to rewire and reprogram them all to be that the car could not be started after 5:00 and had to keep running if on at 4:59:59.

LOL I can think of a way around that... if you have a garage with ventilation at least.

 

[mk42]

You may want your lawyers to go over that method. I was told once by a lawyer that making a machine quit operating at a certain time was considered sabotage.

If you do it the wrong way, sure. If you put a time bomb in the code so they have to call you out every 6 months to "fix" it, yeah, that's not OK. I think you need to at least TRY for it to not be a surprise to the customer, tho if they're just dumb/forgetful that isn't your fault.

If you put in the contract/sales terms exactly what you plan to do (or at least COULD do), you should be good to go. Especially if your whole business model is based around that fact. Note that you can burn a few bridges if you actually enforce it, so you might want to be cautious on actually pulling the trigger unless you have no other choice.

 

[I_Automation]

LOL I can think of a way around that... if you have a garage with ventilation at least.

You and a thousand others.


And that's without a garage as 80% of the houses in Detroit use street parking and 80% of the housing is apartments.


I think they actually abandoned that system completely.

 

[parky]

Reading the originl post, "Stop it functioning if the bill is not paid", one thing if the user disconnects the link ? you will need to ensure with no link the machine will stop, this however, causes all sorts of problems, perhaps if auto stop after a period should inform the user that this is going to happen if bills not paid, how you implement this is going to be a minefield.
Here is just one scenario, assume that auto shutdown if not re-licenced i.e. after x hours the machine will stop unless access on-line to reset the count, user has paid the bill, the link goes down, who pays the bill for lost production.
Perhaps if these systems have HMI's then x hours before re-licence required, the PLC generates a new activation code, this then either means the user has a time in which to contact you or pay the fee, then either, go on-line, re-activate the licence, or the user supplies the re-activation generated code & you give them the new code to re-activate it. (if that makes sense, my brain hurts today).

 

[JesperMP]

Just a comment, that I would not stop the machine entirely.
Only show a message like "license period has expired", and possibly block some of the most fancy functions.
Most of the times that the license does not get renewed will not be because of malicious intent, more often it will be due to forgetfulness, or not knowing how to renew the license, or due to technical issues.
It is important to keep a good rapport with the 99% of the customers that are not trying to cheat you.

edit: Also, to renew the license period in addition to sending a code via the Internet, it would be a good idea to have an alternative method in case there are problems with the internet connection.
For example being able to enter a code on the HMI screen. The code can be sent be email or informed over the phone in an emergency.

 

[I_Automation]

Just a comment, that I would not stop the machine entirely.
Only show a message like "license period has expired", and possibly block some of the most fancy functions.
Most of the times that the license does not get renewed will not be because of malicious intent, more often it will be due to forgetfulness, or not knowing how to renew the license, or due to technical issues...

I was in a circuit board shop and told to fix a piece of equipment in the quality lab that stopped working.


LCD display clearly showed the machine was not going to run because the annual calibration was over 3 months past due. I asked them if it ever showed a warning during the past 3 months and they said they had to clear that warning every 10 minutes for the past 3 months to use the machine.



Plus they got upset when I couldn't plug into the programming plug and reset the timer, and couldn't understand that it had to be done by specific calibration software that only a certified technician would have.


EDIT: This same shop more than once complained that if I had PLC software on my laptop why couldn't I connect to a PLC and make changes. I had Rockwell, Siemen's, Idec, Mitsubishi, Omron, Panasonic, Automation Direct, Saia, Xiinje, Vipa and others, but not the PLC that was in that machine. To them a PLC was a PLC.

 

[drbitboy]

I had Rockwell, Siemen's, Idec, Mitsubishi, Omron, Panasonic, Automation Direct, Saia, Xiinje, Vipa and others, but not the PLC that was in that machine. To them a PLC was a PLC.

LOL.

To them, you were a magician, a la Arthur C. Clarke.