coffee thieft and electronics

[sweducated]

hi,

a cafe has a problem, it keeps having its self service coffee stolen - the actual equipment, money and coffee its self.

i need help designing a pressure pad system to do a few things,

1 monitor the weight of the coffee flask so they can be alerted via a red right when its empty.

2 if there is no weight on that sensor then there will be very noticable alert to staff but not to customers, as the cash box or coffee flask possibly been stolen.

3 log when coffee is taken from the flask and money put into the box so it can be logged with a date and time.

number 1 and number 3 are not essental but would be good if possible the main idea is number 2.

it MUST be very descrete so as to not ruin the atmosphere of the cafe but effective so as to prevent theift.

i figured a simple presure pad would work but i dont know...

 

[BrownOut]

The easiest way would be a simple pushbutton switch. Let the weight of the coffee container engage the switch, and when the container is taken, the switch will open, activating the indicator. Or use a normally closed switch so that when the container is lifted, the switch closes and activates the indicator.

 

[squishy36]

How about something mechanical like a piece of plastic-coated steel cable that ties the pot to the stand using e.g a small padlock? Just enough to help it not grow legs.

 

[sweducated]

im in mensa, thats too simple for me and ruins the atmosphere, says "we dont trust you" so descression is a better way

also im attempting to get a job out of it

 

[BrownOut]

Here is a way to hack a common scale to interface to a computer or controller board https://jdesbonnet.blogspot.com/2010/10/computer-interface-to-low-cost.html The advantage of hacking a scale is you might be able to cut it down to size and hide it under the container.

 

[KeepItSimpleStupid]

Circuit cellar had an article where a load cell was used for the plate. I think it was a warmer and definately within the last two years.

Is RFID an option? Can you rig the doors if the machine moves? In essence, let someone disconnect the coffee maker and start carrying it. When it goes through a door a silent alarm goes off. Catch him/her in the act.


Some other ideas:
1. Load cell to detect the weight of the coffee
2. I don;t know if you can ultrasonically detect level. I don't think so.

 

[picbits]

Put some hidden CCTV in and catch the offender in action - that way there are no arguments when the police are called in.