Connectable

I'm making a smart table with built-in drink cooler and speakers called connectable.

Connectable is run by a raspberry pi which also hosts a website and stores data gathered from the sensors in it's database.

I started out by making a bill of materials to get an idea of what I would need and what it would cost, roughly

when I got the materials I thought I'd need it was time to set up my pi.

Firstly I made the database so I wouldn't need to worry about that later. This database stores all information on the sensors and actuators used in the project. I started out my drawing a rough model in drawio. This way it was easier for me to created the desired tables. I made sure it followed the 3NF standard. This avoids duplicate tables and makes it easy to add tables in the future if you wanted to.

I pushed my dump to GitHub. to use it, just open in with mysql workbench on your ssh connection and run the query. All tables will be created automatically.

After that was done I started drawing the electric schematics. when I was satisfied with them, I drew the finalized versions in fritzing.
One thing to note though is that I bought an l298n double H-bridge instead of building it myself. It's an easy and cheap solution that's guaranteed to work without much trouble.

Once the schematics were done, I could start building the prototype.

I salvaged some old speakers by removing their broken transformer and soldered some wires to the circuit board inside. This way it was easier to use them in my test setup
To find out what voltage they needed, I connected a potentiometer in series with the speakers to slowly ramp up the delivered voltage. Turned out they worked best with a voltage of 3v3.

By removing the transformer it meant that I had an excess power cable which was perfect because I needed one to supply power to my 12V power supply.

Note that this isn't a great solution for the finalized product as the power supply needs to be connected to ground for savety reasons.

The peltier cooler I use has a max supply voltage of 15V, to have it
cool as much as possible I regulated the voltage of the power supply to it's max of 14.2V with the on board regulator. The peltier cooler has a hot and a cold side. You have to make sure to cool the hot side when it's turned on. To optimize cooling I applied some thermal conductive paste to the cooler and heat sink. This makes sure as much heat gets drawn from one to the other.

The CPU cooling fan I use only has a max voltage of 12V. To make sure it gets the right amount of power I soldered two 10Ohm resistors in parallel with each other and connected them to the red wire of the fan. (Some fans have 4 wires, 2 of which are used for speed control but serve no purpose in this project.) To measure the temperature, inside the cooler I'm using a DS18B20 sensor. Be careful connecting to the circuit as the specs show the connections from the bottom! If you want to use the 1-wire sensor, make sure 1 wire is enabled on your raspberry pi. if it isn't , return to step 1.

The rest of the circuit is pretty straight forward.

After the circuit was finished it was time to start programming, I spend a while to get things the way I wanted. it's still not perfect but I'll keep posting updates.

Here is a link to my GitHub.

I designed how I wanted my site to look in adobe XD. Once done, I was ready to create the HTML which you can find on my GitHub as well.

Now the project is almost finished, all that needs to be done is making it look good. Use your imagination! For mine I made a basic design (I will post the measurements later).

first I made the outside of the case, I made sure to leave the side next to the IR receiver open. tµThis way I can add electronics easily.
once done, I cut out the wooden plates and styrofoam (to keep it cool inside). I glued 4 of the faces together.

The bottom and the front pieces need to be detached from the others so the cooler can be opened.