Automatic bar tender : Body frame and electrical building parts

Hey guys, my name is Jérémie and today I ‘am going to speak you about the hardware of our bar tender project. In this video I ‘am going to details how we have made to design all the machine and what material we have used to convert our ideas into a real and functional device.

In this first post, my job is to speak about the mechanical part of the machine then how building the device. The major idea for this project was to only use or to use a maximum of recovered material. Firstly, because we are students and we have limited budget and also to make sure that everyone is able to reproduce our bar tender.

Then we can start with the first step that is to build the body frame of the machine. For this, we have used recovered wooden board from an attic. All the board are shaped into rectangle and joined together with several screws. The size of the structure has been decided by placing 5 bottles aligned and checking the overall length.

When the body frame was fixed to make one piece, we have cut a piece of rigid cardboard and fixed it behind the structure. After we have placed a wood board in front to block the bottles and make sure that it is not possible for the them to go out of the structure.

Once this job has been carried out, it is time to add some wood boards to realize the axle support for the conveyor. They are ready to be perforated and to incorporate the shaft to allow the conveyor to work properly. Moreover, a little piece placed on the top of the body frame is added to create a fixation point for all the piping providing the drink. This component will be detailed forward in the video.

To come back on the shaft support, they are made by inserting à steel pipe surrounded by a PVC one. The diameter of the PVC pipe is slightly wider than the other. That make it free to rotate around the steel pipe. The rotation is possible thanks to the glide between the steel and the PVC.

The next step was to think about the stabilisation of the glass on the conveyor. Then we have carefully cut a thin wood board with a jigsaw and fixed it in the front of the structure. In this case, the conveyor rotates around the axis support and can slide on the wood support to bring stability to the filled glass.

Before inserting the electric motor for the conveyor on the structure, we have took a  MDF plate that is the base of the machine. Thanks to this, we can place the machine wherever we want. Moreover, the structure is reinforced by its fixation on the plate.

After this, the bar tender is ready to be paint, once again, we have chosen a recovered material. That’s why the structure is paint in black.

The final step was to insert auxiliary components on the structure as the pumps, the piping, and all the electronics that command all the operations.

At first, we have perforated the board on the top of the structure and fixed a threaded rod on it. The rod extremity height corresponds at the top of the glass where the liquids are poured. An annular wood board is fixed on this extremity, and 5 holes are perforated where are inserted each pipe. They come from a bottle, go through the pump and finally go out of the pump by a pipe that is inserted in the annular wood board that I was speaking about previously.

We have chosen not to make the piping visible. Then we have put a hold cable duct to insert all the pipes. These pipes are traditional plastic pipes used for all domestic hydraulic applications.

That’s all for the body frame building part. Il leave you with Benoit who will explain the electrical building part. Thanks’ for watching, see you next time!


Hello everyone,

I’m Benoit of the cocktail Team! In this last video, I’m going to explain the electrical building part of our cocktail dispenser.

First, I’m going to make a brief reminder about the listing of the main electrical material needed to make our project functional:

In this project, we have bought 5 centrifugal pumps destinated to an aquarophilia use. Each one is powered in 12DCV and with this voltage, it can reach a flow rate of 240 l/min.

We have also bought 5 Arduino relays, one Genino Arduino (a uno can be adequate for the application). In this project, we have used this object as a slave interface to command all pumps.

Finally, we have used a raspberry PI 3. This device is the most important object in this project because its broadcom chip allows to connect it on a local or online network, furthermore, it allows to manipulate a database because it has a bigger memory than the Arduino. So, it is the brain of our project!

We have bought the pumps on amazon for 5€ each. We have chosen these even though they are really not optimised to this application, because they are low-cost pumps and their flow rate allows to fill the cocktail glass really fast.

We have cut the base connector of each pump and soldered each wire to an Arduino connector. In this way, it’s easier for us to plug these devices on a breadboard.

In the same way, we have cut the connector of an old 12VDc power supply of 500mA and soldered 2 arduino connectors.

Here are the different connections:

First, to power and send the program to the arduino and the raspberry, we have connected these on a laptop by USB.

Then, the arduino connections are pretty basic:

We plug it to a 5VDC sector power supply. As the Arduino is the main device which helps to command the pumps, we must connect each pump on it. However, the power supply voltage of the Arduino and the pumps are different which means that we must pay attention to insulate both supplies between them. Otherwise, we risk to create a short-circuit and to burn all electronic elements. Moreover, we can’t power the pumps with the 5 VDC Arduino supply because it is too low to operate the pumps.

Therefore, we used arduino relays because they create a « galvanic » insulation between the supplies.

As a reminder, a relay is a kind of switch which allows to command an electrical circuit. This switch is operated by a magnetic field which is generated by a self. The self is powered by a secondary circuit which is generally of a lowest voltage than the first one. There isn’t any contact between both circuits and it is that what we called a galvanic insulation.

This is the interest of this device, because we can command a 12VDC circuit by a 5DCV circuit without any risk of short circuit.

The relays have 3 connection pins (VVC – Ground – In) of command circuit by side and 3 others (NO-NC-ground) of power circuit by side. We must plug the Arduino 5VCC on the “VCC” pin and make the same for the ground. The “In” pin must be plugged on an Arduino digital output. The first pins allow to power the relays whereas the last one allows to operate the self.

We have plugged the pumps on the connection “Ground” and “NC”. The plugin is justified because our program activates all pumps at the startup.

To ease the connections, we have used a breadboard to gather all indirect plugins.

So we have connected the power supplies on the track  + and – .

We have finally made the connections like on this schematic (it is not contractual but it’s the main principle):

Capture d_écran 2017-05-22 à 12.43.18

I hope you have now the whole information to make your own cocktail dispenser.

See you soon!

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