Adam W. Chan & Aaron J. Sedine

Automated Bartender
Controls Project

The automated bartender was built to alleviate the work of a typical bartender. Many bar patrons drink the same drinks, so why not have a machine that will dispense the common drinks of choice. The automated bartender is intended to do just that.  The unit was built for personal recreational use, not for a future in public marketing.  For this reason, we have not incorporated a money exchanger or insert within the programming or the machine. This machine was intended for special occasions such as: graduations, weddings, social gatherings, etc.  More specifically a use when the host does not want to bother with mixing drinks and the users are all assumed to be of a legal drinking age if alcohol was to be served.
The user will select their drink choice using one of the two selector switches. A Led will light up when the selector is in the proper location to ensure that the desired selection has been made. Once the selection has been made, the user will have to hold one of the red push buttons until the program times out (machine is done pouring). This was programmed to ensure the user would not push the button and walk away, allowing the beverage to spill.

The purpose of the automated bartender was to familiarize ourselves with real life applications involving PLC’s and also to create a machine that was useful and would actually be used  on a semi-regular basis.


The Automated bartender is constructed of many types of material, most of which can be found at the local Hardware Store.
•Four – 2 gallon containers
•Four – 24 volt, 7 Watt solenoids
•Two – Red push buttons
•One – GE PLC
•Two – Selector switches
•One – Security switch
•Two – Spools 20 gage wire
•Two - 16 gage sheet meal
•Two – Lexan sheets
•Three – Plastic Tee’s
•1/2 and 3/4  inch plastic hose
•Black angle iron
•24 gage sheet metal
The  frame for the dispenser is made of 1.5” x 1.5” x ¼” ASTM angle iron with 24 gage galvanized sheet steel for the body composition.  We used plastic tee’s and ½ and ¾ inch hose to run the liquid from the containers to the dispensing point.  By customizing the spout’s on the gallon containers we were able to regulate the flow of liquid to the end user.  Pour spouts were custom made using 3/8 inch hose and a ball valve solenoid to start and stop flow.  The lexan sheets were used for aesthetic value and serve no structural support.  See attached drawings for machine composition and layout*.
Operational Sequence:

The automated bartender allows a user to select a specific reservoir of liquid by turning a selector dial.  Then by pressing and holding a button, the automated bartender will pour a specific drink. Due to the budget, we had to limit the machine to 10 drink combinations. The machine holds four two-gallon drink dispensers which can be filled with different types of libations. Each container utilizes a solenoid switch and gravitational pull to allow the beverage to flow. The solenoids are regulated by the means of a GE PLC. The automated bartender will be able to accurately pour a desired drink in a matter of seconds.  Once the user pushes the start button it is just a matter of time before gravity pulls the liquids into the hoses and into the users cup.  After receiving the deliverables, the user will simply walk away and the PLC will reset and ready for the next patron.
The following is the basis for our PLC program.  Using this sequence, we designed our PLC program.
         1. User selects from libations bin
                a. container 1 (front right)
                b. container 2 (front left)
                c. container 3 (back right)
                d. container 4 (back left)
                        i. no more than 2 bins can be selected at a time
                        ii. selector switch will designate which drink combination is to be poured
        2. User uses two 5 place selector switches for drink mix
                a. Switch 1, selection 1 = 1
                b. Switch 1, selection 2 = 2
                c. Switch 1, selection 3 = 3
                d. Switch 1, selection 4 = 4
                e. Switch 1, selection 5 = 1 & 2
                f. Switch 2, selection 1 = 1 & 4
                g. Switch 2, selection 2 = 1 & 3
                h. Switch 2, selection 3 = 2 & 4
                i. Switch 2, selection 4 = 2 & 3
                j. Switch 2, selection 5 = 3 & 4
        3. After selection user pushes and holds red “go” button
                a. red “go” button must be held while sequence is initiated or default to “all stop” and reset
                b. two buttons correspond to two switches
                        i. left button goes with left switch
                        ii. right button goes with right switch
                        iii. if  both buttons are pressed, PLC defaults to reset
        4. After drink is poured PLC resets and waits for next command
        5. Lock out stops all functions
                a. natural waiting position and e-stop position for solenoids is in the up or “closed” position
                b. with lock out locked no fluid flows
                c. machine will be locked when fluids need to replenished
                d. machine will be locked when owner does not want machine to operate.
                e. lock removes power from PLC

With the operational sequence completed we analyzed the inputs and outputs.
INPUTS                                                                  OUTPUTS
0 - POUR BUTTON 1                                            20 - SOLENOID 1
1 - SELECTOR POSITION 1                                 21 – SOLENOID 2
2 - SELECTOR POSITION 2                                 22 – SOLENOID 3
3 - SELECTOR POSITION 3                                 23 – SOLENOID 4

One of our main concerns was how we were going to get the solenoids to open and close with the correct amount of pour.  To do this function, we chose to use timers to open and close the solenoids.  We were not sure of how long the solenoids would need to be opened to get the proper amount of pour.  We, therefore, set up the system and manually triggered the solenoids and timed the amount of time to get the proper pour.  Once the data was collected, we were able to set the timers in the PLC to get the proper pour. Wiring the PLC was a very complicated thing.  The wiring schematic* can be seen on the attached drawing.

With the mechanical and electrical components complete there was only one way to know if we had been successful in our venture.  To answer this question we plugged in the machine, grabbed some glasses and slowly worked our way through all the combinations of mixed drinks.  It was an exciting, invigorating and intoxicating means of proving out our own work.  The means of starting with an idea, mechanically building the machine, electrically wiring it, and then programming and having it all work is a beautiful thing.
 The automated bartender layout* can be seen on attached file.

* Link's must be run through AutoCAD 14 or equivalent.