Possible to use PLC to stop employees from stealing

I would like to pick to pick all of your kinds brains for a dilemma that I have.

Dilemma:
- I run a 40 station LAN gaming center.
- People come in, buy X hours worth of game time and pay cash.
- Lately, revenues seem to have fallen off, seemingly uncorrelated to the fact that electricity bill seems to be constant.
- While I use an internet cafe software, I suspect my employees have found a way of disabling it and pocketing the sales themselves. I have no way to confirm this.

Question: Is it possible to control each of the 40 stations using PLC?
- Someone comes in, buys 2 hours worth of game time.
- Instead of the internet cafe software, it will be the PLC software frontend, and my staff activates the electricity into station 5, and set the timer for 2 hours. Every week I need to print reports of the activation and uptime of each station, and by which staff login.
- The sensor/PLC attached to each station will also monitor the electricity usage and uptime of each station, for reporting and cross checking purposes.

I am at the end of my wits. At this rate, I will have to be cashier in the business 24 hours a day, and that's just impossible. I hope that tying in the power delivery to each station via PLC will stop them from stealing.

The only knowledge of PLC I have was being briefly shown my friend's hotel's installation of chillers which was monitored and controlled by GE fanuc PLCs, and it gave me the idea of using PLC's to save my business, and allow me to expand to multiple branches without requiring me to be there all the time.

I understand that I may need to rewire each of the 40 stations individually into a central location for this to happen.

Thank you all!

Sure, you can use a PLC for this. I'd use an HMI screen at the cash to enable a particular computer for XXX minutes (depending what the customer purchased). Passwords could be assigned to each employee, so you could log who enables each machine (also for how long and what date / time).

Individual outputs from the PLC would probably be connected to relays with higher current capacity to control the receptacles the machines are plugged into.

If you want to get really fancy, you could install current-sensing devices (like Hall-effect sensors) to determine current flow and calculate averages, totals, trends, etc. of electricity usage.

Get a PLC with Ethernet capability - easier to connect to modems for remote connection.

Rguimond,

Thanks for your quick response. Can you point me in the right direction as to the brand of sensor and PLC, or the particular model I should look at.

Is there an online store for this kind of thing? I will need to buy the PLC's online and learn the programming and installation myself. Margins on LAN gaming centers are very low and I cannot afford to hire a specialised consultant for the implementation.

Thanks again!

Because your application is not industrial (no safety issues)and that you want to save money as much as you can,you should look into IO card(s) that can read inputs and write outputs directly from an application written in for example VB.net Express (for free).
The nature of your application also requires a bit of database control and reporting. Therefore I also recommend a VB.net kind of enviroment, it's fairly easy to get going if you know a little bit about computers, and there are plenty of examples of "how to" on the web.

I've found the video's of Beth Massi extremely good to find my way in SQL and that kind of stuff.

If you are determined to use a plc, then look at one that can be programmed with low cost or free software (like Codesys).

I think this is not a job for a PLC, but for good ol' gum-shoe investigation.

Have a couple of detectives (aka. friends) go and use your gaming shop (on your expense).
Then check if their usage appear in the log and cash register.
Repeat for each person you have employed to tend the cash register.

Years ago, I was having problems with our boys turning the TV on after hours when they should have been in bed and I solved it using X-10.

I got one of the plug-in modules and cut the cord off of the TV and soldered it directly into the module (I had to make a small hole in the module for the cord, but it went together very nicely.)

Things went well for a time after that, but then the boys complained that the TV wasn't working at all anymore!

I checked things out, and the little heathens had figured out if they switched the address to the module, it would no longer respond to any command coming from my computer.

What tripped them up was that I got lazy one night and instead of switching off just that module, I sent out a command to turn everything on the X-10 system off. Since the module was now re-addressed to the wrong address, the ON command didn't work either. Actually I was pretty proud of the little buggers for figuring this out.

Since I didn't want to have to turn everything off just to make sure that the TV went off at the right time, I took the module apart for a second time and soldered in the house code so that the selector switches on the front wouldn't work any more. I left the selector switches in just so that would have something to twiddle, not that it did them any good...

That would be one way to solve the problem, but personally I would use a supervisory PC to control the network and disable the LAN connection and the keyboard when the time was up. This way you wouldn't be shutting down your PCs all day long (think of the wear and tear on the PC, not to mention the reboot time!).

Using Linux on the supervisory PC would be a good choice, but you should bounce this off of some IT guys to see what they think of it.

If I did use a PLC at all, I would have it open up the network connection and the keyboard using relay contacts. I wouldn't shut the power off to the PC.

To be honest; a PLC is not your solution.
As others have suggested: find out who is guilty of stealing from you. Perhaps an ip-cam (cheap and chearfull!) to see what's going on in combination with remotely logging into your icafe client.

Thanks for the advice guys!

I did try the camera but what I need to catch is not someone who is paying cash at the counter, that's part of normal operation.

What needs to be recorded is for a customer to come to a station that's unlocked, not having the internet cafe software gui, upon login, and thus the cash can be pocketed without being monitored.

This is harder to capture. My particular camera compensates for the low ambient lighting and thus the screens are overexposed most of the time. Not to mention optimal camera placements, as one camera won't be able to cover more than a few stations.

Thanks for the suggestions, please keep them coming if you can think of something else. I shall do my research into all the methods everyone have shared above. ...the thought of having a LAN gaming center controlled by PLCs has merit in its own extreme way.

malmal said:

What needs to be recorded is for a customer to come to a station that's unlocked, not having the internet cafe software gui, upon login, and thus the cash can be pocketed without being monitored.

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I think your best bet is to ask a network/security expert. It must be possible to secure the PC's so that they only work when the software is running.

What you need is software to log who enables a power point (this should only be done with a password) and logs the time each point is enabled, which should correspond with the above logging.

I'm also unsure if a PLC is the best solution here or new more secure PC software and a database.

Better internet cafe software might be the answer, searching the net there are plenty out there.

Yeah, it is more question about incompetent software. Maybe theyre booting off usb stick or disk.. I would put those cameras so that you can see what happens on gaming stations.

What features does the current software you use have? What kinda priviliges do you have when logged in? Can you use the USB ports?

rootboy said:

This way you wouldn't be shutting down your PCs all day long (think of the wear and tear on the PC, not to mention the reboot time!).

Click to expand...

Yes. Cycling power repeatedly is very hard on equipment.